From: Vsevolod Stakhov <vsevolod@rspamd.com>
Date: Mon, 29 Dec 2025 22:13:25 +0000 (+0000)
Subject: [Project] Update fmt library to 12.1.0
X-Git-Tag: 3.14.3~21
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ed113cede183592e4fe9cd37213d524149fb269c;p=thirdparty%2Frspamd.git

[Project] Update fmt library to 12.1.0

Also restore doctest/scripts/version.txt removed in previous commit.
---

diff --git a/contrib/DEPENDENCY_INFO.md b/contrib/DEPENDENCY_INFO.md
index fc41c07a3d..8e7cb8e797 100644
--- a/contrib/DEPENDENCY_INFO.md
+++ b/contrib/DEPENDENCY_INFO.md
@@ -32,7 +32,7 @@
 | simdutf                | ef7d39c | Apache 2            | NO      | build system only   |
 | expected               | v1.0    | Public Domain / CC0 | NO      |                     |
 | frozen                 | 1.0.1   | Apache 2            | NO      |                     |
-| fmt                    | 11.0.0  | MIT                 | NO      |                     |
+| fmt                    | 12.1.0  | MIT                 | NO      |                     |
 | doctest                | 2.4.11  | MIT                 | NO      |                     |
 | function2              | 4.1.0   | Boost               | NO      |                     |
 | ankerl/svector         | 1.0.2   | MIT                 | NO      |                     |
diff --git a/contrib/doctest/scripts/version.txt b/contrib/doctest/scripts/version.txt
new file mode 100644
index 0000000000..e393c3c556
--- /dev/null
+++ b/contrib/doctest/scripts/version.txt
@@ -0,0 +1 @@
+2.4.11
\ No newline at end of file
diff --git a/contrib/fmt/LICENSE.rst b/contrib/fmt/LICENSE.rst
index f0ec3db4d2..1cd1ef9269 100644
--- a/contrib/fmt/LICENSE.rst
+++ b/contrib/fmt/LICENSE.rst
@@ -1,4 +1,4 @@
-Copyright (c) 2012 - present, Victor Zverovich
+Copyright (c) 2012 - present, Victor Zverovich and {fmt} contributors
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/contrib/fmt/include/fmt/args.h b/contrib/fmt/include/fmt/args.h
index 31a60e8faf..5e5f40f9eb 100644
--- a/contrib/fmt/include/fmt/args.h
+++ b/contrib/fmt/include/fmt/args.h
@@ -17,7 +17,6 @@
 #include "format.h"  // std_string_view
 
 FMT_BEGIN_NAMESPACE
-
 namespace detail {
 
 template <typename T> struct is_reference_wrapper : std::false_type {};
@@ -72,19 +71,13 @@ class dynamic_arg_list {
  * It can be implicitly converted into `fmt::basic_format_args` for passing
  * into type-erased formatting functions such as `fmt::vformat`.
  */
-template <typename Context>
-class dynamic_format_arg_store
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
-    // Workaround a GCC template argument substitution bug.
-    : public basic_format_args<Context>
-#endif
-{
+FMT_EXPORT template <typename Context> class dynamic_format_arg_store {
  private:
   using char_type = typename Context::char_type;
 
   template <typename T> struct need_copy {
     static constexpr detail::type mapped_type =
-        detail::mapped_type_constant<T, Context>::value;
+        detail::mapped_type_constant<T, char_type>::value;
 
     enum {
       value = !(detail::is_reference_wrapper<T>::value ||
@@ -97,7 +90,7 @@ class dynamic_format_arg_store
   };
 
   template <typename T>
-  using stored_type = conditional_t<
+  using stored_t = conditional_t<
       std::is_convertible<T, std::basic_string<char_type>>::value &&
           !detail::is_reference_wrapper<T>::value,
       std::basic_string<char_type>, T>;
@@ -112,41 +105,37 @@ class dynamic_format_arg_store
 
   friend class basic_format_args<Context>;
 
-  auto get_types() const -> unsigned long long {
-    return detail::is_unpacked_bit | data_.size() |
-           (named_info_.empty()
-                ? 0ULL
-                : static_cast<unsigned long long>(detail::has_named_args_bit));
-  }
-
   auto data() const -> const basic_format_arg<Context>* {
     return named_info_.empty() ? data_.data() : data_.data() + 1;
   }
 
   template <typename T> void emplace_arg(const T& arg) {
-    data_.emplace_back(detail::make_arg<Context>(arg));
+    data_.emplace_back(arg);
   }
 
   template <typename T>
   void emplace_arg(const detail::named_arg<char_type, T>& arg) {
-    if (named_info_.empty()) {
-      constexpr const detail::named_arg_info<char_type>* zero_ptr{nullptr};
-      data_.insert(data_.begin(), {zero_ptr, 0});
-    }
-    data_.emplace_back(detail::make_arg<Context>(detail::unwrap(arg.value)));
+    if (named_info_.empty())
+      data_.insert(data_.begin(), basic_format_arg<Context>(nullptr, 0));
+    data_.emplace_back(detail::unwrap(arg.value));
     auto pop_one = [](std::vector<basic_format_arg<Context>>* data) {
       data->pop_back();
     };
     std::unique_ptr<std::vector<basic_format_arg<Context>>, decltype(pop_one)>
         guard{&data_, pop_one};
     named_info_.push_back({arg.name, static_cast<int>(data_.size() - 2u)});
-    data_[0].value_.named_args = {named_info_.data(), named_info_.size()};
+    data_[0] = {named_info_.data(), named_info_.size()};
     guard.release();
   }
 
  public:
   constexpr dynamic_format_arg_store() = default;
 
+  operator basic_format_args<Context>() const {
+    return basic_format_args<Context>(data(), static_cast<int>(data_.size()),
+                                      !named_info_.empty());
+  }
+
   /**
    * Adds an argument into the dynamic store for later passing to a formatting
    * function.
@@ -164,7 +153,7 @@ class dynamic_format_arg_store
    */
   template <typename T> void push_back(const T& arg) {
     if (detail::const_check(need_copy<T>::value))
-      emplace_arg(dynamic_args_.push<stored_type<T>>(arg));
+      emplace_arg(dynamic_args_.push<stored_t<T>>(arg));
     else
       emplace_arg(detail::unwrap(arg));
   }
@@ -200,7 +189,7 @@ class dynamic_format_arg_store
         dynamic_args_.push<std::basic_string<char_type>>(arg.name).c_str();
     if (detail::const_check(need_copy<T>::value)) {
       emplace_arg(
-          fmt::arg(arg_name, dynamic_args_.push<stored_type<T>>(arg.value)));
+          fmt::arg(arg_name, dynamic_args_.push<stored_t<T>>(arg.value)));
     } else {
       emplace_arg(fmt::arg(arg_name, arg.value));
     }
@@ -210,17 +199,20 @@ class dynamic_format_arg_store
   void clear() {
     data_.clear();
     named_info_.clear();
-    dynamic_args_ = detail::dynamic_arg_list();
+    dynamic_args_ = {};
   }
 
   /// Reserves space to store at least `new_cap` arguments including
   /// `new_cap_named` named arguments.
   void reserve(size_t new_cap, size_t new_cap_named) {
     FMT_ASSERT(new_cap >= new_cap_named,
-               "Set of arguments includes set of named arguments");
+               "set of arguments includes set of named arguments");
     data_.reserve(new_cap);
     named_info_.reserve(new_cap_named);
   }
+
+  /// Returns the number of elements in the store.
+  auto size() const noexcept -> size_t { return data_.size(); }
 };
 
 FMT_END_NAMESPACE
diff --git a/contrib/fmt/include/fmt/base.h b/contrib/fmt/include/fmt/base.h
index 976402a42b..0d57867782 100644
--- a/contrib/fmt/include/fmt/base.h
+++ b/contrib/fmt/include/fmt/base.h
@@ -15,15 +15,13 @@
 #ifndef FMT_MODULE
 #  include <limits.h>  // CHAR_BIT
 #  include <stdio.h>   // FILE
-#  include <string.h>  // strlen
+#  include <string.h>  // memcmp
 
-// <cstddef> is also included transitively from <type_traits>.
-#  include <cstddef>      // std::byte
 #  include <type_traits>  // std::enable_if
 #endif
 
 // The fmt library version in the form major * 10000 + minor * 100 + patch.
-#define FMT_VERSION 110000
+#define FMT_VERSION 120100
 
 // Detect compiler versions.
 #if defined(__clang__) && !defined(__ibmxl__)
@@ -78,6 +76,11 @@
 #else
 #  define FMT_HAS_INCLUDE(x) 0
 #endif
+#ifdef __has_builtin
+#  define FMT_HAS_BUILTIN(x) __has_builtin(x)
+#else
+#  define FMT_HAS_BUILTIN(x) 0
+#endif
 #ifdef __has_cpp_attribute
 #  define FMT_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
 #else
@@ -93,9 +96,9 @@
 // Detect C++14 relaxed constexpr.
 #ifdef FMT_USE_CONSTEXPR
 // Use the provided definition.
-#elif FMT_GCC_VERSION >= 600 && FMT_CPLUSPLUS >= 201402L
-// GCC only allows throw in constexpr since version 6:
-// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67371.
+#elif FMT_GCC_VERSION >= 702 && FMT_CPLUSPLUS >= 201402L
+// GCC only allows constexpr member functions in non-literal types since 7.2:
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66297.
 #  define FMT_USE_CONSTEXPR 1
 #elif FMT_ICC_VERSION
 #  define FMT_USE_CONSTEXPR 0  // https://github.com/fmtlib/fmt/issues/1628
@@ -111,7 +114,9 @@
 #endif
 
 // Detect consteval, C++20 constexpr extensions and std::is_constant_evaluated.
-#if !defined(__cpp_lib_is_constant_evaluated)
+#ifdef FMT_USE_CONSTEVAL
+// Use the provided definition.
+#elif !defined(__cpp_lib_is_constant_evaluated)
 #  define FMT_USE_CONSTEVAL 0
 #elif FMT_CPLUSPLUS < 201709L
 #  define FMT_USE_CONSTEVAL 0
@@ -138,40 +143,19 @@
 #  define FMT_CONSTEXPR20
 #endif
 
-#if defined(FMT_USE_NONTYPE_TEMPLATE_ARGS)
-// Use the provided definition.
-#elif defined(__NVCOMPILER)
-#  define FMT_USE_NONTYPE_TEMPLATE_ARGS 0
-#elif FMT_GCC_VERSION >= 903 && FMT_CPLUSPLUS >= 201709L
-#  define FMT_USE_NONTYPE_TEMPLATE_ARGS 1
-#elif defined(__cpp_nontype_template_args) && \
-    __cpp_nontype_template_args >= 201911L
-#  define FMT_USE_NONTYPE_TEMPLATE_ARGS 1
-#elif FMT_CLANG_VERSION >= 1200 && FMT_CPLUSPLUS >= 202002L
-#  define FMT_USE_NONTYPE_TEMPLATE_ARGS 1
-#else
-#  define FMT_USE_NONTYPE_TEMPLATE_ARGS 0
-#endif
-
-#ifdef FMT_USE_CONCEPTS
-// Use the provided definition.
-#elif defined(__cpp_concepts)
-#  define FMT_USE_CONCEPTS 1
-#else
-#  define FMT_USE_CONCEPTS 0
-#endif
-
 // Check if exceptions are disabled.
-#ifdef FMT_EXCEPTIONS
+#ifdef FMT_USE_EXCEPTIONS
 // Use the provided definition.
 #elif defined(__GNUC__) && !defined(__EXCEPTIONS)
-#  define FMT_EXCEPTIONS 0
+#  define FMT_USE_EXCEPTIONS 0
+#elif defined(__clang__) && !defined(__cpp_exceptions)
+#  define FMT_USE_EXCEPTIONS 0
 #elif FMT_MSC_VERSION && !_HAS_EXCEPTIONS
-#  define FMT_EXCEPTIONS 0
+#  define FMT_USE_EXCEPTIONS 0
 #else
-#  define FMT_EXCEPTIONS 1
+#  define FMT_USE_EXCEPTIONS 1
 #endif
-#if FMT_EXCEPTIONS
+#if FMT_USE_EXCEPTIONS
 #  define FMT_TRY try
 #  define FMT_CATCH(x) catch (x)
 #else
@@ -179,6 +163,20 @@
 #  define FMT_CATCH(x) if (false)
 #endif
 
+#ifdef FMT_NO_UNIQUE_ADDRESS
+// Use the provided definition.
+#elif FMT_CPLUSPLUS < 202002L
+// Not supported.
+#elif FMT_HAS_CPP_ATTRIBUTE(no_unique_address)
+#  define FMT_NO_UNIQUE_ADDRESS [[no_unique_address]]
+// VS2019 v16.10 and later except clang-cl (https://reviews.llvm.org/D110485).
+#elif FMT_MSC_VERSION >= 1929 && !FMT_CLANG_VERSION
+#  define FMT_NO_UNIQUE_ADDRESS [[msvc::no_unique_address]]
+#endif
+#ifndef FMT_NO_UNIQUE_ADDRESS
+#  define FMT_NO_UNIQUE_ADDRESS
+#endif
+
 #if FMT_HAS_CPP17_ATTRIBUTE(fallthrough)
 #  define FMT_FALLTHROUGH [[fallthrough]]
 #elif defined(__clang__)
@@ -197,34 +195,12 @@
 #  define FMT_NORETURN
 #endif
 
-#ifndef FMT_NODISCARD
-#  if FMT_HAS_CPP17_ATTRIBUTE(nodiscard)
-#    define FMT_NODISCARD [[nodiscard]]
-#  else
-#    define FMT_NODISCARD
-#  endif
-#endif
-
-#ifdef FMT_DEPRECATED
-// Use the provided definition.
-#elif FMT_HAS_CPP14_ATTRIBUTE(deprecated)
-#  define FMT_DEPRECATED [[deprecated]]
-#else
-#  define FMT_DEPRECATED /* deprecated */
-#endif
-
-#ifdef FMT_INLINE
+#ifdef FMT_NODISCARD
 // Use the provided definition.
-#elif FMT_GCC_VERSION || FMT_CLANG_VERSION
-#  define FMT_ALWAYS_INLINE inline __attribute__((always_inline))
+#elif FMT_HAS_CPP17_ATTRIBUTE(nodiscard)
+#  define FMT_NODISCARD [[nodiscard]]
 #else
-#  define FMT_ALWAYS_INLINE inline
-#endif
-// A version of FMT_INLINE to prevent code bloat in debug mode.
-#ifdef NDEBUG
-#  define FMT_INLINE FMT_ALWAYS_INLINE
-#else
-#  define FMT_INLINE inline
+#  define FMT_NODISCARD
 #endif
 
 #if FMT_GCC_VERSION || FMT_CLANG_VERSION
@@ -233,36 +209,53 @@
 #  define FMT_VISIBILITY(value)
 #endif
 
-#ifndef FMT_GCC_PRAGMA
+// Detect pragmas.
+#define FMT_PRAGMA_IMPL(x) _Pragma(#x)
+#if FMT_GCC_VERSION >= 504 && !defined(__NVCOMPILER)
 // Workaround a _Pragma bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59884
 // and an nvhpc warning: https://github.com/fmtlib/fmt/pull/2582.
-#  if FMT_GCC_VERSION >= 504 && !defined(__NVCOMPILER)
-#    define FMT_GCC_PRAGMA(arg) _Pragma(arg)
-#  else
-#    define FMT_GCC_PRAGMA(arg)
-#  endif
+#  define FMT_PRAGMA_GCC(x) FMT_PRAGMA_IMPL(GCC x)
+#else
+#  define FMT_PRAGMA_GCC(x)
 #endif
-
-// GCC < 5 requires this-> in decltype.
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 500
-#  define FMT_DECLTYPE_THIS this->
+#if FMT_CLANG_VERSION
+#  define FMT_PRAGMA_CLANG(x) FMT_PRAGMA_IMPL(clang x)
 #else
-#  define FMT_DECLTYPE_THIS
+#  define FMT_PRAGMA_CLANG(x)
 #endif
-
 #if FMT_MSC_VERSION
 #  define FMT_MSC_WARNING(...) __pragma(warning(__VA_ARGS__))
-#  define FMT_UNCHECKED_ITERATOR(It) \
-    using _Unchecked_type = It  // Mark iterator as checked.
 #else
 #  define FMT_MSC_WARNING(...)
-#  define FMT_UNCHECKED_ITERATOR(It) using unchecked_type = It
+#endif
+
+// Enable minimal optimizations for more compact code in debug mode.
+FMT_PRAGMA_GCC(push_options)
+#if !defined(__OPTIMIZE__) && !defined(__CUDACC__) && !defined(FMT_MODULE)
+FMT_PRAGMA_GCC(optimize("Og"))
+#  define FMT_GCC_OPTIMIZED
+#endif
+FMT_PRAGMA_CLANG(diagnostic push)
+FMT_PRAGMA_GCC(diagnostic push)
+
+#ifdef FMT_ALWAYS_INLINE
+// Use the provided definition.
+#elif FMT_GCC_VERSION || FMT_CLANG_VERSION
+#  define FMT_ALWAYS_INLINE inline __attribute__((always_inline))
+#else
+#  define FMT_ALWAYS_INLINE inline
+#endif
+// A version of FMT_ALWAYS_INLINE to prevent code bloat in debug mode.
+#if defined(NDEBUG) || defined(FMT_GCC_OPTIMIZED)
+#  define FMT_INLINE FMT_ALWAYS_INLINE
+#else
+#  define FMT_INLINE inline
 #endif
 
 #ifndef FMT_BEGIN_NAMESPACE
 #  define FMT_BEGIN_NAMESPACE \
     namespace fmt {           \
-    inline namespace v10 {
+    inline namespace v12 {
 #  define FMT_END_NAMESPACE \
     }                       \
     }
@@ -274,7 +267,13 @@
 #  define FMT_END_EXPORT
 #endif
 
-#if !defined(FMT_HEADER_ONLY) && defined(_WIN32)
+#ifdef _WIN32
+#  define FMT_WIN32 1
+#else
+#  define FMT_WIN32 0
+#endif
+
+#if !defined(FMT_HEADER_ONLY) && FMT_WIN32
 #  if defined(FMT_LIB_EXPORT)
 #    define FMT_API __declspec(dllexport)
 #  elif defined(FMT_SHARED)
@@ -287,28 +286,19 @@
 #  define FMT_API
 #endif
 
-#ifndef FMT_UNICODE
-#  define FMT_UNICODE 1
+#ifndef FMT_OPTIMIZE_SIZE
+#  define FMT_OPTIMIZE_SIZE 0
 #endif
 
-// Check if rtti is available.
-#ifndef FMT_USE_RTTI
-// __RTTI is for EDG compilers. _CPPRTTI is for MSVC.
-#  if defined(__GXX_RTTI) || FMT_HAS_FEATURE(cxx_rtti) || defined(_CPPRTTI) || \
-      defined(__INTEL_RTTI__) || defined(__RTTI)
-#    define FMT_USE_RTTI 1
-#  else
-#    define FMT_USE_RTTI 0
-#  endif
+// FMT_BUILTIN_TYPE=0 may result in smaller library size at the cost of higher
+// per-call binary size by passing built-in types through the extension API.
+#ifndef FMT_BUILTIN_TYPES
+#  define FMT_BUILTIN_TYPES 1
 #endif
 
-#define FMT_FWD(...) static_cast<decltype(__VA_ARGS__)&&>(__VA_ARGS__)
-
-// Enable minimal optimizations for more compact code in debug mode.
-FMT_GCC_PRAGMA("GCC push_options")
-#if !defined(__OPTIMIZE__) && !defined(__CUDACC__)
-FMT_GCC_PRAGMA("GCC optimize(\"Og\")")
-#endif
+#define FMT_APPLY_VARIADIC(expr) \
+  using unused = int[];          \
+  (void)unused { 0, (expr, 0)... }
 
 FMT_BEGIN_NAMESPACE
 
@@ -324,17 +314,15 @@ template <typename T>
 using remove_const_t = typename std::remove_const<T>::type;
 template <typename T>
 using remove_cvref_t = typename std::remove_cv<remove_reference_t<T>>::type;
-template <typename T> struct type_identity {
-  using type = T;
-};
-template <typename T> using type_identity_t = typename type_identity<T>::type;
 template <typename T>
 using make_unsigned_t = typename std::make_unsigned<T>::type;
 template <typename T>
 using underlying_t = typename std::underlying_type<T>::type;
+template <typename T> using decay_t = typename std::decay<T>::type;
+using nullptr_t = decltype(nullptr);
 
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 500
-// A workaround for gcc 4.8 to make void_t work in a SFINAE context.
+#if (FMT_GCC_VERSION && FMT_GCC_VERSION < 500) || FMT_MSC_VERSION
+// A workaround for gcc 4.9 & MSVC v141 to make void_t work in a SFINAE context.
 template <typename...> struct void_t_impl {
   using type = void;
 };
@@ -356,14 +344,15 @@ struct monostate {
 #  define FMT_ENABLE_IF(...) fmt::enable_if_t<(__VA_ARGS__), int> = 0
 #endif
 
-// This is defined in base.h instead of format.h to avoid injecting in std.
-// It is a template to avoid undesirable implicit conversions to std::byte.
-#ifdef __cpp_lib_byte
-template <typename T, FMT_ENABLE_IF(std::is_same<T, std::byte>::value)>
-inline auto format_as(T b) -> unsigned char {
-  return static_cast<unsigned char>(b);
+template <typename T> constexpr auto min_of(T a, T b) -> T {
+  return a < b ? a : b;
 }
-#endif
+template <typename T> constexpr auto max_of(T a, T b) -> T {
+  return a > b ? a : b;
+}
+
+FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
+                                      const char* message);
 
 namespace detail {
 // Suppresses "unused variable" warnings with the method described in
@@ -373,9 +362,8 @@ template <typename... T> FMT_CONSTEXPR void ignore_unused(const T&...) {}
 
 constexpr auto is_constant_evaluated(bool default_value = false) noexcept
     -> bool {
-// Workaround for incompatibility between libstdc++ consteval-based
-// std::is_constant_evaluated() implementation and clang-14:
-// https://github.com/fmtlib/fmt/issues/3247.
+// Workaround for incompatibility between clang 14 and libstdc++ consteval-based
+// std::is_constant_evaluated: https://github.com/fmtlib/fmt/issues/3247.
 #if FMT_CPLUSPLUS >= 202002L && FMT_GLIBCXX_RELEASE >= 12 && \
     (FMT_CLANG_VERSION >= 1400 && FMT_CLANG_VERSION < 1500)
   ignore_unused(default_value);
@@ -389,7 +377,9 @@ constexpr auto is_constant_evaluated(bool default_value = false) noexcept
 }
 
 // Suppresses "conditional expression is constant" warnings.
-template <typename T> constexpr auto const_check(T value) -> T { return value; }
+template <typename T> FMT_ALWAYS_INLINE constexpr auto const_check(T val) -> T {
+  return val;
+}
 
 FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
                                       const char* message);
@@ -404,19 +394,18 @@ FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
 #  define FMT_ASSERT(condition, message)                                    \
     ((condition) /* void() fails with -Winvalid-constexpr on clang 4.0.1 */ \
          ? (void)0                                                          \
-         : fmt::detail::assert_fail(__FILE__, __LINE__, (message)))
+         : ::fmt::assert_fail(__FILE__, __LINE__, (message)))
 #endif
 
 #ifdef FMT_USE_INT128
-// Do nothing.
+// Use the provided definition.
 #elif defined(__SIZEOF_INT128__) && !defined(__NVCC__) && \
     !(FMT_CLANG_VERSION && FMT_MSC_VERSION)
 #  define FMT_USE_INT128 1
 using int128_opt = __int128_t;  // An optional native 128-bit integer.
 using uint128_opt = __uint128_t;
-template <typename T> inline auto convert_for_visit(T value) -> T {
-  return value;
-}
+inline auto map(int128_opt x) -> int128_opt { return x; }
+inline auto map(uint128_opt x) -> uint128_opt { return x; }
 #else
 #  define FMT_USE_INT128 0
 #endif
@@ -424,9 +413,27 @@ template <typename T> inline auto convert_for_visit(T value) -> T {
 enum class int128_opt {};
 enum class uint128_opt {};
 // Reduce template instantiations.
-template <typename T> auto convert_for_visit(T) -> monostate { return {}; }
+inline auto map(int128_opt) -> monostate { return {}; }
+inline auto map(uint128_opt) -> monostate { return {}; }
+#endif
+
+#ifdef FMT_USE_BITINT
+// Use the provided definition.
+#elif FMT_CLANG_VERSION >= 1500 && !defined(__CUDACC__)
+#  define FMT_USE_BITINT 1
+#else
+#  define FMT_USE_BITINT 0
 #endif
 
+#if FMT_USE_BITINT
+FMT_PRAGMA_CLANG(diagnostic ignored "-Wbit-int-extension")
+template <int N> using bitint = _BitInt(N);
+template <int N> using ubitint = unsigned _BitInt(N);
+#else
+template <int N> struct bitint {};
+template <int N> struct ubitint {};
+#endif  // FMT_USE_BITINT
+
 // Casts a nonnegative integer to unsigned.
 template <typename Int>
 FMT_CONSTEXPR auto to_unsigned(Int value) -> make_unsigned_t<Int> {
@@ -434,6 +441,9 @@ FMT_CONSTEXPR auto to_unsigned(Int value) -> make_unsigned_t<Int> {
   return static_cast<make_unsigned_t<Int>>(value);
 }
 
+template <typename Char>
+using unsigned_char = conditional_t<sizeof(Char) == 1, unsigned char, unsigned>;
+
 // A heuristic to detect std::string and std::[experimental::]string_view.
 // It is mainly used to avoid dependency on <[experimental/]string_view>.
 template <typename T, typename Enable = void>
@@ -441,31 +451,28 @@ struct is_std_string_like : std::false_type {};
 template <typename T>
 struct is_std_string_like<T, void_t<decltype(std::declval<T>().find_first_of(
                                  typename T::value_type(), 0))>>
-    : std::true_type {};
+    : std::is_convertible<decltype(std::declval<T>().data()),
+                          const typename T::value_type*> {};
 
-// Returns true iff the literal encoding is UTF-8.
-constexpr auto is_utf8_enabled() -> bool {
-  // Avoid an MSVC sign extension bug: https://github.com/fmtlib/fmt/pull/2297.
-  using uchar = unsigned char;
-  return sizeof("\u00A7") == 3 && uchar("\u00A7"[0]) == 0xC2 &&
-         uchar("\u00A7"[1]) == 0xA7;
-}
-constexpr auto use_utf8() -> bool {
-  return !FMT_MSC_VERSION || is_utf8_enabled();
-}
+// Check if the literal encoding is UTF-8.
+enum { is_utf8_enabled = "\u00A7"[1] == '\xA7' };
+enum { use_utf8 = !FMT_WIN32 || is_utf8_enabled };
+
+#ifndef FMT_UNICODE
+#  define FMT_UNICODE 1
+#endif
 
-static_assert(!FMT_UNICODE || use_utf8(),
+static_assert(!FMT_UNICODE || use_utf8,
               "Unicode support requires compiling with /utf-8");
 
-template <typename Char> FMT_CONSTEXPR auto length(const Char* s) -> size_t {
-  size_t len = 0;
-  while (*s++) ++len;
-  return len;
+template <typename T> constexpr auto narrow(T*) -> char* { return nullptr; }
+constexpr FMT_ALWAYS_INLINE auto narrow(const char* s) -> const char* {
+  return s;
 }
 
 template <typename Char>
-FMT_CONSTEXPR auto compare(const Char* s1, const Char* s2, std::size_t n)
-    -> int {
+FMT_CONSTEXPR auto compare(const Char* s1, const Char* s2, size_t n) -> int {
+  if (!is_constant_evaluated() && sizeof(Char) == 1) return memcmp(s1, s2, n);
   for (; n != 0; ++s1, ++s2, --n) {
     if (*s1 < *s2) return -1;
     if (*s1 > *s2) return 1;
@@ -473,28 +480,37 @@ FMT_CONSTEXPR auto compare(const Char* s1, const Char* s2, std::size_t n)
   return 0;
 }
 
+namespace adl {
+using namespace std;
+
+template <typename Container>
+auto invoke_back_inserter()
+    -> decltype(back_inserter(std::declval<Container&>()));
+}  // namespace adl
+
 template <typename It, typename Enable = std::true_type>
 struct is_back_insert_iterator : std::false_type {};
+
 template <typename It>
 struct is_back_insert_iterator<
-    It,
-    bool_constant<std::is_same<
-        decltype(back_inserter(std::declval<typename It::container_type&>())),
-        It>::value>> : std::true_type {};
+    It, bool_constant<std::is_same<
+            decltype(adl::invoke_back_inserter<typename It::container_type>()),
+            It>::value>> : std::true_type {};
 
 // Extracts a reference to the container from *insert_iterator.
 template <typename OutputIt>
-inline auto get_container(OutputIt it) -> typename OutputIt::container_type& {
+inline FMT_CONSTEXPR20 auto get_container(OutputIt it) ->
+    typename OutputIt::container_type& {
   struct accessor : OutputIt {
-    accessor(OutputIt base) : OutputIt(base) {}
+    FMT_CONSTEXPR20 accessor(OutputIt base) : OutputIt(base) {}
     using OutputIt::container;
   };
   return *accessor(it).container;
 }
 }  // namespace detail
 
-// Checks whether T is a container with contiguous storage.
-template <typename T> struct is_contiguous : std::false_type {};
+// Parsing-related public API and forward declarations.
+FMT_BEGIN_EXPORT
 
 /**
  * An implementation of `std::basic_string_view` for pre-C++17. It provides a
@@ -503,7 +519,6 @@ template <typename T> struct is_contiguous : std::false_type {};
  * compiled with a different `-std` option than the client code (which is not
  * recommended).
  */
-FMT_EXPORT
 template <typename Char> class basic_string_view {
  private:
   const Char* data_;
@@ -515,22 +530,29 @@ template <typename Char> class basic_string_view {
 
   constexpr basic_string_view() noexcept : data_(nullptr), size_(0) {}
 
-  /// Constructs a string reference object from a C string and a size.
+  /// Constructs a string view object from a C string and a size.
   constexpr basic_string_view(const Char* s, size_t count) noexcept
       : data_(s), size_(count) {}
 
-  constexpr basic_string_view(std::nullptr_t) = delete;
+  constexpr basic_string_view(nullptr_t) = delete;
 
-  /// Constructs a string reference object from a C string.
-  FMT_CONSTEXPR20
-  basic_string_view(const Char* s)
-      : data_(s),
-        size_(detail::const_check(std::is_same<Char, char>::value &&
-                                  !detail::is_constant_evaluated(false))
-                  ? strlen(reinterpret_cast<const char*>(s))
-                  : detail::length(s)) {}
-
-  /// Constructs a string reference from a `std::basic_string` or a
+  /// Constructs a string view object from a C string.
+#if FMT_GCC_VERSION
+  FMT_ALWAYS_INLINE
+#endif
+  FMT_CONSTEXPR20 basic_string_view(const Char* s) : data_(s) {
+#if FMT_HAS_BUILTIN(__builtin_strlen) || FMT_GCC_VERSION || FMT_CLANG_VERSION
+    if (std::is_same<Char, char>::value && !detail::is_constant_evaluated()) {
+      size_ = __builtin_strlen(detail::narrow(s));  // strlen is not constexpr.
+      return;
+    }
+#endif
+    size_t len = 0;
+    while (*s++) ++len;
+    size_ = len;
+  }
+
+  /// Constructs a string view from a `std::basic_string` or a
   /// `std::basic_string_view` object.
   template <typename S,
             FMT_ENABLE_IF(detail::is_std_string_like<S>::value&& std::is_same<
@@ -567,13 +589,11 @@ template <typename Char> class basic_string_view {
     return starts_with(basic_string_view<Char>(s));
   }
 
-  // Lexicographically compare this string reference to other.
   FMT_CONSTEXPR auto compare(basic_string_view other) const -> int {
-    size_t str_size = size_ < other.size_ ? size_ : other.size_;
-    int result = detail::compare(data_, other.data_, str_size);
-    if (result == 0)
-      result = size_ == other.size_ ? 0 : (size_ < other.size_ ? -1 : 1);
-    return result;
+    int result =
+        detail::compare(data_, other.data_, min_of(size_, other.size_));
+    if (result != 0) return result;
+    return size_ == other.size_ ? 0 : (size_ < other.size_ ? -1 : 1);
   }
 
   FMT_CONSTEXPR friend auto operator==(basic_string_view lhs,
@@ -597,179 +617,274 @@ template <typename Char> class basic_string_view {
   }
 };
 
-FMT_EXPORT
 using string_view = basic_string_view<char>;
 
-/// Specifies if `T` is a character type. Can be specialized by users.
-FMT_EXPORT
-template <typename T> struct is_char : std::false_type {};
-template <> struct is_char<char> : std::true_type {};
-
-namespace detail {
-
-// Constructs fmt::basic_string_view<Char> from types implicitly convertible
-// to it, deducing Char. Explicitly convertible types such as the ones returned
-// from FMT_STRING are intentionally excluded.
-template <typename Char, FMT_ENABLE_IF(is_char<Char>::value)>
-auto to_string_view(const Char* s) -> basic_string_view<Char> {
-  return s;
-}
-template <typename T, FMT_ENABLE_IF(is_std_string_like<T>::value)>
-auto to_string_view(const T& s) -> basic_string_view<typename T::value_type> {
-  return s;
-}
-template <typename Char>
-constexpr auto to_string_view(basic_string_view<Char> s)
-    -> basic_string_view<Char> {
-  return s;
-}
-
-template <typename T, typename Enable = void>
-struct has_to_string_view : std::false_type {};
-// detail:: is intentional since to_string_view is not an extension point.
-template <typename T>
-struct has_to_string_view<
-    T, void_t<decltype(detail::to_string_view(std::declval<T>()))>>
-    : std::true_type {};
-
-template <typename Char, Char... C> struct string_literal {
-  static constexpr Char value[sizeof...(C)] = {C...};
-  constexpr operator basic_string_view<Char>() const {
-    return {value, sizeof...(C)};
-  }
-};
-#if FMT_CPLUSPLUS < 201703L
-template <typename Char, Char... C>
-constexpr Char string_literal<Char, C...>::value[sizeof...(C)];
-#endif
+template <typename T> class basic_appender;
+using appender = basic_appender<char>;
 
-enum class type {
-  none_type,
-  // Integer types should go first,
-  int_type,
-  uint_type,
-  long_long_type,
-  ulong_long_type,
-  int128_type,
-  uint128_type,
-  bool_type,
-  char_type,
-  last_integer_type = char_type,
-  // followed by floating-point types.
-  float_type,
-  double_type,
-  long_double_type,
-  last_numeric_type = long_double_type,
-  cstring_type,
-  string_type,
-  pointer_type,
-  custom_type
-};
+// Checks whether T is a container with contiguous storage.
+template <typename T> struct is_contiguous : std::false_type {};
 
-// Maps core type T to the corresponding type enum constant.
-template <typename T, typename Char>
-struct type_constant : std::integral_constant<type, type::custom_type> {};
+class context;
+template <typename OutputIt, typename Char> class generic_context;
+template <typename Char> class parse_context;
 
-#define FMT_TYPE_CONSTANT(Type, constant) \
-  template <typename Char>                \
-  struct type_constant<Type, Char>        \
-      : std::integral_constant<type, type::constant> {}
+// Longer aliases for C++20 compatibility.
+template <typename Char> using basic_format_parse_context = parse_context<Char>;
+using format_parse_context = parse_context<char>;
+template <typename OutputIt, typename Char>
+using basic_format_context =
+    conditional_t<std::is_same<OutputIt, appender>::value, context,
+                  generic_context<OutputIt, Char>>;
+using format_context = context;
 
-FMT_TYPE_CONSTANT(int, int_type);
-FMT_TYPE_CONSTANT(unsigned, uint_type);
-FMT_TYPE_CONSTANT(long long, long_long_type);
-FMT_TYPE_CONSTANT(unsigned long long, ulong_long_type);
-FMT_TYPE_CONSTANT(int128_opt, int128_type);
-FMT_TYPE_CONSTANT(uint128_opt, uint128_type);
-FMT_TYPE_CONSTANT(bool, bool_type);
-FMT_TYPE_CONSTANT(Char, char_type);
-FMT_TYPE_CONSTANT(float, float_type);
-FMT_TYPE_CONSTANT(double, double_type);
-FMT_TYPE_CONSTANT(long double, long_double_type);
-FMT_TYPE_CONSTANT(const Char*, cstring_type);
-FMT_TYPE_CONSTANT(basic_string_view<Char>, string_type);
-FMT_TYPE_CONSTANT(const void*, pointer_type);
+template <typename Char>
+using buffered_context =
+    conditional_t<std::is_same<Char, char>::value, context,
+                  generic_context<basic_appender<Char>, Char>>;
 
-constexpr auto is_integral_type(type t) -> bool {
-  return t > type::none_type && t <= type::last_integer_type;
-}
-constexpr auto is_arithmetic_type(type t) -> bool {
-  return t > type::none_type && t <= type::last_numeric_type;
-}
+template <typename Context> class basic_format_arg;
+template <typename Context> class basic_format_args;
 
-constexpr auto set(type rhs) -> int { return 1 << static_cast<int>(rhs); }
-constexpr auto in(type t, int set) -> bool {
-  return ((set >> static_cast<int>(t)) & 1) != 0;
-}
+// A separate type would result in shorter symbols but break ABI compatibility
+// between clang and gcc on ARM (#1919).
+using format_args = basic_format_args<context>;
 
-// Bitsets of types.
-enum {
-  sint_set =
-      set(type::int_type) | set(type::long_long_type) | set(type::int128_type),
-  uint_set = set(type::uint_type) | set(type::ulong_long_type) |
-             set(type::uint128_type),
-  bool_set = set(type::bool_type),
-  char_set = set(type::char_type),
-  float_set = set(type::float_type) | set(type::double_type) |
-              set(type::long_double_type),
-  string_set = set(type::string_type),
-  cstring_set = set(type::cstring_type),
-  pointer_set = set(type::pointer_type)
+// A formatter for objects of type T.
+template <typename T, typename Char = char, typename Enable = void>
+struct formatter {
+  // A deleted default constructor indicates a disabled formatter.
+  formatter() = delete;
 };
-}  // namespace detail
 
 /// Reports a format error at compile time or, via a `format_error` exception,
 /// at runtime.
 // This function is intentionally not constexpr to give a compile-time error.
 FMT_NORETURN FMT_API void report_error(const char* message);
 
-FMT_DEPRECATED FMT_NORETURN inline void throw_format_error(
-    const char* message) {
-  report_error(message);
-}
+enum class presentation_type : unsigned char {
+  // Common specifiers:
+  none = 0,
+  debug = 1,   // '?'
+  string = 2,  // 's' (string, bool)
 
-/// String's character (code unit) type.
-template <typename S,
-          typename V = decltype(detail::to_string_view(std::declval<S>()))>
-using char_t = typename V::value_type;
+  // Integral, bool and character specifiers:
+  dec = 3,  // 'd'
+  hex,      // 'x' or 'X'
+  oct,      // 'o'
+  bin,      // 'b' or 'B'
+  chr,      // 'c'
 
-/**
- * Parsing context consisting of a format string range being parsed and an
- * argument counter for automatic indexing.
- * You can use the `format_parse_context` type alias for `char` instead.
- */
-FMT_EXPORT
-template <typename Char> class basic_format_parse_context {
+  // String and pointer specifiers:
+  pointer = 3,  // 'p'
+
+  // Floating-point specifiers:
+  exp = 1,  // 'e' or 'E' (1 since there is no FP debug presentation)
+  fixed,    // 'f' or 'F'
+  general,  // 'g' or 'G'
+  hexfloat  // 'a' or 'A'
+};
+
+enum class align { none, left, right, center, numeric };
+enum class sign { none, minus, plus, space };
+enum class arg_id_kind { none, index, name };
+
+// Basic format specifiers for built-in and string types.
+class basic_specs {
  private:
-  basic_string_view<Char> format_str_;
-  int next_arg_id_;
+  // Data is arranged as follows:
+  //
+  //  0                   1                   2                   3
+  //  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+  // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+  // |type |align| w | p | s |u|#|L|  f  |          unused           |
+  // +-----+-----+---+---+---+-+-+-+-----+---------------------------+
+  //
+  //   w - dynamic width info
+  //   p - dynamic precision info
+  //   s - sign
+  //   u - uppercase (e.g. 'X' for 'x')
+  //   # - alternate form ('#')
+  //   L - localized
+  //   f - fill size
+  //
+  // Bitfields are not used because of compiler bugs such as gcc bug 61414.
+  enum : unsigned {
+    type_mask = 0x00007,
+    align_mask = 0x00038,
+    width_mask = 0x000C0,
+    precision_mask = 0x00300,
+    sign_mask = 0x00C00,
+    uppercase_mask = 0x01000,
+    alternate_mask = 0x02000,
+    localized_mask = 0x04000,
+    fill_size_mask = 0x38000,
+
+    align_shift = 3,
+    width_shift = 6,
+    precision_shift = 8,
+    sign_shift = 10,
+    fill_size_shift = 15,
+
+    max_fill_size = 4
+  };
 
-  FMT_CONSTEXPR void do_check_arg_id(int id);
+  unsigned data_ = 1 << fill_size_shift;
+  static_assert(sizeof(basic_specs::data_) * CHAR_BIT >= 18, "");
 
- public:
-  using char_type = Char;
-  using iterator = const Char*;
+  // Character (code unit) type is erased to prevent template bloat.
+  char fill_data_[max_fill_size] = {' '};
 
-  explicit constexpr basic_format_parse_context(
-      basic_string_view<Char> format_str, int next_arg_id = 0)
-      : format_str_(format_str), next_arg_id_(next_arg_id) {}
+  FMT_CONSTEXPR void set_fill_size(size_t size) {
+    data_ = (data_ & ~fill_size_mask) |
+            (static_cast<unsigned>(size) << fill_size_shift);
+  }
 
-  /// Returns an iterator to the beginning of the format string range being
-  /// parsed.
-  constexpr auto begin() const noexcept -> iterator {
-    return format_str_.begin();
+ public:
+  constexpr auto type() const -> presentation_type {
+    return static_cast<presentation_type>(data_ & type_mask);
+  }
+  FMT_CONSTEXPR void set_type(presentation_type t) {
+    data_ = (data_ & ~type_mask) | static_cast<unsigned>(t);
   }
 
-  /// Returns an iterator past the end of the format string range being parsed.
-  constexpr auto end() const noexcept -> iterator { return format_str_.end(); }
+  constexpr auto align() const -> align {
+    return static_cast<fmt::align>((data_ & align_mask) >> align_shift);
+  }
+  FMT_CONSTEXPR void set_align(fmt::align a) {
+    data_ = (data_ & ~align_mask) | (static_cast<unsigned>(a) << align_shift);
+  }
 
-  /// Advances the begin iterator to `it`.
-  FMT_CONSTEXPR void advance_to(iterator it) {
-    format_str_.remove_prefix(detail::to_unsigned(it - begin()));
+  constexpr auto dynamic_width() const -> arg_id_kind {
+    return static_cast<arg_id_kind>((data_ & width_mask) >> width_shift);
+  }
+  FMT_CONSTEXPR void set_dynamic_width(arg_id_kind w) {
+    data_ = (data_ & ~width_mask) | (static_cast<unsigned>(w) << width_shift);
   }
 
-  /// Reports an error if using the manual argument indexing; otherwise returns
-  /// the next argument index and switches to the automatic indexing.
+  FMT_CONSTEXPR auto dynamic_precision() const -> arg_id_kind {
+    return static_cast<arg_id_kind>((data_ & precision_mask) >>
+                                    precision_shift);
+  }
+  FMT_CONSTEXPR void set_dynamic_precision(arg_id_kind p) {
+    data_ = (data_ & ~precision_mask) |
+            (static_cast<unsigned>(p) << precision_shift);
+  }
+
+  constexpr auto dynamic() const -> bool {
+    return (data_ & (width_mask | precision_mask)) != 0;
+  }
+
+  constexpr auto sign() const -> sign {
+    return static_cast<fmt::sign>((data_ & sign_mask) >> sign_shift);
+  }
+  FMT_CONSTEXPR void set_sign(fmt::sign s) {
+    data_ = (data_ & ~sign_mask) | (static_cast<unsigned>(s) << sign_shift);
+  }
+
+  constexpr auto upper() const -> bool { return (data_ & uppercase_mask) != 0; }
+  FMT_CONSTEXPR void set_upper() { data_ |= uppercase_mask; }
+
+  constexpr auto alt() const -> bool { return (data_ & alternate_mask) != 0; }
+  FMT_CONSTEXPR void set_alt() { data_ |= alternate_mask; }
+  FMT_CONSTEXPR void clear_alt() { data_ &= ~alternate_mask; }
+
+  constexpr auto localized() const -> bool {
+    return (data_ & localized_mask) != 0;
+  }
+  FMT_CONSTEXPR void set_localized() { data_ |= localized_mask; }
+
+  constexpr auto fill_size() const -> size_t {
+    return (data_ & fill_size_mask) >> fill_size_shift;
+  }
+
+  template <typename Char, FMT_ENABLE_IF(std::is_same<Char, char>::value)>
+  constexpr auto fill() const -> const Char* {
+    return fill_data_;
+  }
+  template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+  constexpr auto fill() const -> const Char* {
+    return nullptr;
+  }
+
+  template <typename Char> constexpr auto fill_unit() const -> Char {
+    using uchar = unsigned char;
+    return static_cast<Char>(static_cast<uchar>(fill_data_[0]) |
+                             (static_cast<uchar>(fill_data_[1]) << 8) |
+                             (static_cast<uchar>(fill_data_[2]) << 16));
+  }
+
+  FMT_CONSTEXPR void set_fill(char c) {
+    fill_data_[0] = c;
+    set_fill_size(1);
+  }
+
+  template <typename Char>
+  FMT_CONSTEXPR void set_fill(basic_string_view<Char> s) {
+    auto size = s.size();
+    set_fill_size(size);
+    if (size == 1) {
+      unsigned uchar = static_cast<detail::unsigned_char<Char>>(s[0]);
+      fill_data_[0] = static_cast<char>(uchar);
+      fill_data_[1] = static_cast<char>(uchar >> 8);
+      fill_data_[2] = static_cast<char>(uchar >> 16);
+      return;
+    }
+    FMT_ASSERT(size <= max_fill_size, "invalid fill");
+    for (size_t i = 0; i < size; ++i)
+      fill_data_[i & 3] = static_cast<char>(s[i]);
+  }
+
+  FMT_CONSTEXPR void copy_fill_from(const basic_specs& specs) {
+    set_fill_size(specs.fill_size());
+    for (size_t i = 0; i < max_fill_size; ++i)
+      fill_data_[i] = specs.fill_data_[i];
+  }
+};
+
+// Format specifiers for built-in and string types.
+struct format_specs : basic_specs {
+  int width;
+  int precision;
+
+  constexpr format_specs() : width(0), precision(-1) {}
+};
+
+/**
+ * Parsing context consisting of a format string range being parsed and an
+ * argument counter for automatic indexing.
+ */
+template <typename Char = char> class parse_context {
+ private:
+  basic_string_view<Char> fmt_;
+  int next_arg_id_;
+
+  enum { use_constexpr_cast = !FMT_GCC_VERSION || FMT_GCC_VERSION >= 1200 };
+
+  FMT_CONSTEXPR void do_check_arg_id(int arg_id);
+
+ public:
+  using char_type = Char;
+  using iterator = const Char*;
+
+  constexpr explicit parse_context(basic_string_view<Char> fmt,
+                                   int next_arg_id = 0)
+      : fmt_(fmt), next_arg_id_(next_arg_id) {}
+
+  /// Returns an iterator to the beginning of the format string range being
+  /// parsed.
+  constexpr auto begin() const noexcept -> iterator { return fmt_.begin(); }
+
+  /// Returns an iterator past the end of the format string range being parsed.
+  constexpr auto end() const noexcept -> iterator { return fmt_.end(); }
+
+  /// Advances the begin iterator to `it`.
+  FMT_CONSTEXPR void advance_to(iterator it) {
+    fmt_.remove_prefix(detail::to_unsigned(it - begin()));
+  }
+
+  /// Reports an error if using the manual argument indexing; otherwise returns
+  /// the next argument index and switches to the automatic indexing.
   FMT_CONSTEXPR auto next_arg_id() -> int {
     if (next_arg_id_ < 0) {
       report_error("cannot switch from manual to automatic argument indexing");
@@ -796,23 +911,357 @@ template <typename Char> class basic_format_parse_context {
   FMT_CONSTEXPR void check_dynamic_spec(int arg_id);
 };
 
-FMT_EXPORT
-using format_parse_context = basic_format_parse_context<char>;
+#ifndef FMT_USE_LOCALE
+#  define FMT_USE_LOCALE (FMT_OPTIMIZE_SIZE <= 1)
+#endif
+
+// A type-erased reference to std::locale to avoid the heavy <locale> include.
+class locale_ref {
+#if FMT_USE_LOCALE
+ private:
+  const void* locale_;  // A type-erased pointer to std::locale.
+
+ public:
+  constexpr locale_ref() : locale_(nullptr) {}
+
+  template <typename Locale, FMT_ENABLE_IF(sizeof(Locale::collate) != 0)>
+  locale_ref(const Locale& loc) : locale_(&loc) {
+    // Check if std::isalpha is found via ADL to reduce the chance of misuse.
+    isalpha('x', loc);
+  }
+
+  inline explicit operator bool() const noexcept { return locale_ != nullptr; }
+#endif  // FMT_USE_LOCALE
+
+ public:
+  template <typename Locale> auto get() const -> Locale;
+};
+
+FMT_END_EXPORT
 
 namespace detail {
+
+// Specifies if `T` is a code unit type.
+template <typename T> struct is_code_unit : std::false_type {};
+template <> struct is_code_unit<char> : std::true_type {};
+template <> struct is_code_unit<wchar_t> : std::true_type {};
+template <> struct is_code_unit<char16_t> : std::true_type {};
+template <> struct is_code_unit<char32_t> : std::true_type {};
+#ifdef __cpp_char8_t
+template <> struct is_code_unit<char8_t> : bool_constant<is_utf8_enabled> {};
+#endif
+
+// Constructs fmt::basic_string_view<Char> from types implicitly convertible
+// to it, deducing Char. Explicitly convertible types such as the ones returned
+// from FMT_STRING are intentionally excluded.
+template <typename Char, FMT_ENABLE_IF(is_code_unit<Char>::value)>
+constexpr auto to_string_view(const Char* s) -> basic_string_view<Char> {
+  return s;
+}
+template <typename T, FMT_ENABLE_IF(is_std_string_like<T>::value)>
+constexpr auto to_string_view(const T& s)
+    -> basic_string_view<typename T::value_type> {
+  return s;
+}
+template <typename Char>
+constexpr auto to_string_view(basic_string_view<Char> s)
+    -> basic_string_view<Char> {
+  return s;
+}
+
+template <typename T, typename Enable = void>
+struct has_to_string_view : std::false_type {};
+// detail:: is intentional since to_string_view is not an extension point.
+template <typename T>
+struct has_to_string_view<
+    T, void_t<decltype(detail::to_string_view(std::declval<T>()))>>
+    : std::true_type {};
+
+/// String's character (code unit) type. detail:: is intentional to prevent ADL.
+template <typename S,
+          typename V = decltype(detail::to_string_view(std::declval<S>()))>
+using char_t = typename V::value_type;
+
+enum class type {
+  none_type,
+  // Integer types should go first,
+  int_type,
+  uint_type,
+  long_long_type,
+  ulong_long_type,
+  int128_type,
+  uint128_type,
+  bool_type,
+  char_type,
+  last_integer_type = char_type,
+  // followed by floating-point types.
+  float_type,
+  double_type,
+  long_double_type,
+  last_numeric_type = long_double_type,
+  cstring_type,
+  string_type,
+  pointer_type,
+  custom_type
+};
+
+// Maps core type T to the corresponding type enum constant.
+template <typename T, typename Char>
+struct type_constant : std::integral_constant<type, type::custom_type> {};
+
+#define FMT_TYPE_CONSTANT(Type, constant) \
+  template <typename Char>                \
+  struct type_constant<Type, Char>        \
+      : std::integral_constant<type, type::constant> {}
+
+FMT_TYPE_CONSTANT(int, int_type);
+FMT_TYPE_CONSTANT(unsigned, uint_type);
+FMT_TYPE_CONSTANT(long long, long_long_type);
+FMT_TYPE_CONSTANT(unsigned long long, ulong_long_type);
+FMT_TYPE_CONSTANT(int128_opt, int128_type);
+FMT_TYPE_CONSTANT(uint128_opt, uint128_type);
+FMT_TYPE_CONSTANT(bool, bool_type);
+FMT_TYPE_CONSTANT(Char, char_type);
+FMT_TYPE_CONSTANT(float, float_type);
+FMT_TYPE_CONSTANT(double, double_type);
+FMT_TYPE_CONSTANT(long double, long_double_type);
+FMT_TYPE_CONSTANT(const Char*, cstring_type);
+FMT_TYPE_CONSTANT(basic_string_view<Char>, string_type);
+FMT_TYPE_CONSTANT(const void*, pointer_type);
+
+constexpr auto is_integral_type(type t) -> bool {
+  return t > type::none_type && t <= type::last_integer_type;
+}
+constexpr auto is_arithmetic_type(type t) -> bool {
+  return t > type::none_type && t <= type::last_numeric_type;
+}
+
+constexpr auto set(type rhs) -> int { return 1 << static_cast<int>(rhs); }
+constexpr auto in(type t, int set) -> bool {
+  return ((set >> static_cast<int>(t)) & 1) != 0;
+}
+
+// Bitsets of types.
+enum {
+  sint_set =
+      set(type::int_type) | set(type::long_long_type) | set(type::int128_type),
+  uint_set = set(type::uint_type) | set(type::ulong_long_type) |
+             set(type::uint128_type),
+  bool_set = set(type::bool_type),
+  char_set = set(type::char_type),
+  float_set = set(type::float_type) | set(type::double_type) |
+              set(type::long_double_type),
+  string_set = set(type::string_type),
+  cstring_set = set(type::cstring_type),
+  pointer_set = set(type::pointer_type)
+};
+
+struct view {};
+
+template <typename T, typename Enable = std::true_type>
+struct is_view : std::false_type {};
+template <typename T>
+struct is_view<T, bool_constant<sizeof(T) != 0>> : std::is_base_of<view, T> {};
+
+template <typename Char, typename T> struct named_arg;
+template <typename T> struct is_named_arg : std::false_type {};
+template <typename T> struct is_static_named_arg : std::false_type {};
+
+template <typename Char, typename T>
+struct is_named_arg<named_arg<Char, T>> : std::true_type {};
+
+template <typename Char, typename T> struct named_arg : view {
+  const Char* name;
+  const T& value;
+
+  named_arg(const Char* n, const T& v) : name(n), value(v) {}
+  static_assert(!is_named_arg<T>::value, "nested named arguments");
+};
+
+template <bool B = false> constexpr auto count() -> int { return B ? 1 : 0; }
+template <bool B1, bool B2, bool... Tail> constexpr auto count() -> int {
+  return (B1 ? 1 : 0) + count<B2, Tail...>();
+}
+
+template <typename... T> constexpr auto count_named_args() -> int {
+  return count<is_named_arg<T>::value...>();
+}
+template <typename... T> constexpr auto count_static_named_args() -> int {
+  return count<is_static_named_arg<T>::value...>();
+}
+
+template <typename Char> struct named_arg_info {
+  const Char* name;
+  int id;
+};
+
+// named_args is non-const to suppress a bogus -Wmaybe-uninitialized in gcc 13.
+template <typename Char>
+FMT_CONSTEXPR void check_for_duplicate(named_arg_info<Char>* named_args,
+                                       int named_arg_index,
+                                       basic_string_view<Char> arg_name) {
+  for (int i = 0; i < named_arg_index; ++i) {
+    if (named_args[i].name == arg_name) report_error("duplicate named arg");
+  }
+}
+
+template <typename Char, typename T, FMT_ENABLE_IF(!is_named_arg<T>::value)>
+void init_named_arg(named_arg_info<Char>*, int& arg_index, int&, const T&) {
+  ++arg_index;
+}
+template <typename Char, typename T, FMT_ENABLE_IF(is_named_arg<T>::value)>
+void init_named_arg(named_arg_info<Char>* named_args, int& arg_index,
+                    int& named_arg_index, const T& arg) {
+  check_for_duplicate<Char>(named_args, named_arg_index, arg.name);
+  named_args[named_arg_index++] = {arg.name, arg_index++};
+}
+
+template <typename T, typename Char,
+          FMT_ENABLE_IF(!is_static_named_arg<T>::value)>
+FMT_CONSTEXPR void init_static_named_arg(named_arg_info<Char>*, int& arg_index,
+                                         int&) {
+  ++arg_index;
+}
+template <typename T, typename Char,
+          FMT_ENABLE_IF(is_static_named_arg<T>::value)>
+FMT_CONSTEXPR void init_static_named_arg(named_arg_info<Char>* named_args,
+                                         int& arg_index, int& named_arg_index) {
+  check_for_duplicate<Char>(named_args, named_arg_index, T::name);
+  named_args[named_arg_index++] = {T::name, arg_index++};
+}
+
+// To minimize the number of types we need to deal with, long is translated
+// either to int or to long long depending on its size.
+enum { long_short = sizeof(long) == sizeof(int) && FMT_BUILTIN_TYPES };
+using long_type = conditional_t<long_short, int, long long>;
+using ulong_type = conditional_t<long_short, unsigned, unsigned long long>;
+
+template <typename T>
+using format_as_result =
+    remove_cvref_t<decltype(format_as(std::declval<const T&>()))>;
+template <typename T>
+using format_as_member_result =
+    remove_cvref_t<decltype(formatter<T>::format_as(std::declval<const T&>()))>;
+
+template <typename T, typename Enable = std::true_type>
+struct use_format_as : std::false_type {};
+// format_as member is only used to avoid injection into the std namespace.
+template <typename T, typename Enable = std::true_type>
+struct use_format_as_member : std::false_type {};
+
+// Only map owning types because mapping views can be unsafe.
+template <typename T>
+struct use_format_as<
+    T, bool_constant<std::is_arithmetic<format_as_result<T>>::value>>
+    : std::true_type {};
+template <typename T>
+struct use_format_as_member<
+    T, bool_constant<std::is_arithmetic<format_as_member_result<T>>::value>>
+    : std::true_type {};
+
+template <typename T, typename U = remove_const_t<T>>
+using use_formatter =
+    bool_constant<(std::is_class<T>::value || std::is_enum<T>::value ||
+                   std::is_union<T>::value || std::is_array<T>::value) &&
+                  !has_to_string_view<T>::value && !is_named_arg<T>::value &&
+                  !use_format_as<T>::value && !use_format_as_member<U>::value>;
+
+template <typename Char, typename T, typename U = remove_const_t<T>>
+auto has_formatter_impl(T* p, buffered_context<Char>* ctx = nullptr)
+    -> decltype(formatter<U, Char>().format(*p, *ctx), std::true_type());
+template <typename Char> auto has_formatter_impl(...) -> std::false_type;
+
+// T can be const-qualified to check if it is const-formattable.
+template <typename T, typename Char> constexpr auto has_formatter() -> bool {
+  return decltype(has_formatter_impl<Char>(static_cast<T*>(nullptr)))::value;
+}
+
+// Maps formatting argument types to natively supported types or user-defined
+// types with formatters. Returns void on errors to be SFINAE-friendly.
+template <typename Char> struct type_mapper {
+  static auto map(signed char) -> int;
+  static auto map(unsigned char) -> unsigned;
+  static auto map(short) -> int;
+  static auto map(unsigned short) -> unsigned;
+  static auto map(int) -> int;
+  static auto map(unsigned) -> unsigned;
+  static auto map(long) -> long_type;
+  static auto map(unsigned long) -> ulong_type;
+  static auto map(long long) -> long long;
+  static auto map(unsigned long long) -> unsigned long long;
+  static auto map(int128_opt) -> int128_opt;
+  static auto map(uint128_opt) -> uint128_opt;
+  static auto map(bool) -> bool;
+
+  template <int N>
+  static auto map(bitint<N>) -> conditional_t<N <= 64, long long, void>;
+  template <int N>
+  static auto map(ubitint<N>)
+      -> conditional_t<N <= 64, unsigned long long, void>;
+
+  template <typename T, FMT_ENABLE_IF(is_code_unit<T>::value)>
+  static auto map(T) -> conditional_t<
+      std::is_same<T, char>::value || std::is_same<T, Char>::value, Char, void>;
+
+  static auto map(float) -> float;
+  static auto map(double) -> double;
+  static auto map(long double) -> long double;
+
+  static auto map(Char*) -> const Char*;
+  static auto map(const Char*) -> const Char*;
+  template <typename T, typename C = char_t<T>,
+            FMT_ENABLE_IF(!std::is_pointer<T>::value)>
+  static auto map(const T&) -> conditional_t<std::is_same<C, Char>::value,
+                                             basic_string_view<C>, void>;
+
+  static auto map(void*) -> const void*;
+  static auto map(const void*) -> const void*;
+  static auto map(volatile void*) -> const void*;
+  static auto map(const volatile void*) -> const void*;
+  static auto map(nullptr_t) -> const void*;
+  template <typename T, FMT_ENABLE_IF(std::is_pointer<T>::value ||
+                                      std::is_member_pointer<T>::value)>
+  static auto map(const T&) -> void;
+
+  template <typename T, FMT_ENABLE_IF(use_format_as<T>::value)>
+  static auto map(const T& x) -> decltype(map(format_as(x)));
+  template <typename T, FMT_ENABLE_IF(use_format_as_member<T>::value)>
+  static auto map(const T& x) -> decltype(map(formatter<T>::format_as(x)));
+
+  template <typename T, FMT_ENABLE_IF(use_formatter<T>::value)>
+  static auto map(T&) -> conditional_t<has_formatter<T, Char>(), T&, void>;
+
+  template <typename T, FMT_ENABLE_IF(is_named_arg<T>::value)>
+  static auto map(const T& named_arg) -> decltype(map(named_arg.value));
+};
+
+// detail:: is used to workaround a bug in MSVC 2017.
+template <typename T, typename Char>
+using mapped_t = decltype(detail::type_mapper<Char>::map(std::declval<T&>()));
+
+// A type constant after applying type_mapper.
+template <typename T, typename Char = char>
+using mapped_type_constant = type_constant<mapped_t<T, Char>, Char>;
+
+template <typename T, typename Context,
+          type TYPE =
+              mapped_type_constant<T, typename Context::char_type>::value>
+using stored_type_constant = std::integral_constant<
+    type, Context::builtin_types || TYPE == type::int_type ? TYPE
+                                                           : type::custom_type>;
 // A parse context with extra data used only in compile-time checks.
 template <typename Char>
-class compile_parse_context : public basic_format_parse_context<Char> {
+class compile_parse_context : public parse_context<Char> {
  private:
   int num_args_;
   const type* types_;
-  using base = basic_format_parse_context<Char>;
+  using base = parse_context<Char>;
 
  public:
-  explicit FMT_CONSTEXPR compile_parse_context(
-      basic_string_view<Char> format_str, int num_args, const type* types,
-      int next_arg_id = 0)
-      : base(format_str, next_arg_id), num_args_(num_args), types_(types) {}
+  FMT_CONSTEXPR explicit compile_parse_context(basic_string_view<Char> fmt,
+                                               int num_args, const type* types,
+                                               int next_arg_id = 0)
+      : base(fmt, next_arg_id), num_args_(num_args), types_(types) {}
 
   constexpr auto num_args() const -> int { return num_args_; }
   constexpr auto arg_type(int id) const -> type { return types_[id]; }
@@ -830,2005 +1279,1528 @@ class compile_parse_context : public basic_format_parse_context<Char> {
   using base::check_arg_id;
 
   FMT_CONSTEXPR void check_dynamic_spec(int arg_id) {
-    detail::ignore_unused(arg_id);
+    ignore_unused(arg_id);
     if (arg_id < num_args_ && types_ && !is_integral_type(types_[arg_id]))
       report_error("width/precision is not integer");
   }
 };
 
-/// A contiguous memory buffer with an optional growing ability. It is an
-/// internal class and shouldn't be used directly, only via `memory_buffer`.
-template <typename T> class buffer {
- private:
-  T* ptr_;
-  size_t size_;
-  size_t capacity_;
-
-  using grow_fun = void (*)(buffer& buf, size_t capacity);
-  grow_fun grow_;
-
- protected:
-  // Don't initialize ptr_ since it is not accessed to save a few cycles.
-  FMT_MSC_WARNING(suppress : 26495)
-  FMT_CONSTEXPR20 buffer(grow_fun grow, size_t sz) noexcept
-      : size_(sz), capacity_(sz), grow_(grow) {}
-
-  constexpr buffer(grow_fun grow, T* p = nullptr, size_t sz = 0,
-                   size_t cap = 0) noexcept
-      : ptr_(p), size_(sz), capacity_(cap), grow_(grow) {}
-
-  FMT_CONSTEXPR20 ~buffer() = default;
-  buffer(buffer&&) = default;
-
-  /// Sets the buffer data and capacity.
-  FMT_CONSTEXPR void set(T* buf_data, size_t buf_capacity) noexcept {
-    ptr_ = buf_data;
-    capacity_ = buf_capacity;
-  }
-
- public:
-  using value_type = T;
-  using const_reference = const T&;
-
-  buffer(const buffer&) = delete;
-  void operator=(const buffer&) = delete;
-
-  auto begin() noexcept -> T* { return ptr_; }
-  auto end() noexcept -> T* { return ptr_ + size_; }
-
-  auto begin() const noexcept -> const T* { return ptr_; }
-  auto end() const noexcept -> const T* { return ptr_ + size_; }
-
-  /// Returns the size of this buffer.
-  constexpr auto size() const noexcept -> size_t { return size_; }
-
-  /// Returns the capacity of this buffer.
-  constexpr auto capacity() const noexcept -> size_t { return capacity_; }
-
-  /// Returns a pointer to the buffer data (not null-terminated).
-  FMT_CONSTEXPR auto data() noexcept -> T* { return ptr_; }
-  FMT_CONSTEXPR auto data() const noexcept -> const T* { return ptr_; }
-
-  /// Clears this buffer.
-  void clear() { size_ = 0; }
-
-  // Tries resizing the buffer to contain `count` elements. If T is a POD type
-  // the new elements may not be initialized.
-  FMT_CONSTEXPR void try_resize(size_t count) {
-    try_reserve(count);
-    size_ = count <= capacity_ ? count : capacity_;
-  }
-
-  // Tries increasing the buffer capacity to `new_capacity`. It can increase the
-  // capacity by a smaller amount than requested but guarantees there is space
-  // for at least one additional element either by increasing the capacity or by
-  // flushing the buffer if it is full.
-  FMT_CONSTEXPR void try_reserve(size_t new_capacity) {
-    if (new_capacity > capacity_) grow_(*this, new_capacity);
-  }
-
-  FMT_CONSTEXPR void push_back(const T& value) {
-    try_reserve(size_ + 1);
-    ptr_[size_++] = value;
-  }
-
-  /// Appends data to the end of the buffer.
-  template <typename U> void append(const U* begin, const U* end) {
-    while (begin != end) {
-      auto count = to_unsigned(end - begin);
-      try_reserve(size_ + count);
-      auto free_cap = capacity_ - size_;
-      if (free_cap < count) count = free_cap;
-      if (std::is_same<T, U>::value) {
-        memcpy(ptr_ + size_, begin, count * sizeof(T));
-      } else {
-        T* out = ptr_ + size_;
-        for (size_t i = 0; i < count; ++i) out[i] = begin[i];
-      }
-      size_ += count;
-      begin += count;
-    }
-  }
-
-  template <typename Idx> FMT_CONSTEXPR auto operator[](Idx index) -> T& {
-    return ptr_[index];
-  }
-  template <typename Idx>
-  FMT_CONSTEXPR auto operator[](Idx index) const -> const T& {
-    return ptr_[index];
-  }
-};
-
-struct buffer_traits {
-  explicit buffer_traits(size_t) {}
-  auto count() const -> size_t { return 0; }
-  auto limit(size_t size) -> size_t { return size; }
-};
-
-class fixed_buffer_traits {
- private:
-  size_t count_ = 0;
-  size_t limit_;
-
- public:
-  explicit fixed_buffer_traits(size_t limit) : limit_(limit) {}
-  auto count() const -> size_t { return count_; }
-  auto limit(size_t size) -> size_t {
-    size_t n = limit_ > count_ ? limit_ - count_ : 0;
-    count_ += size;
-    return size < n ? size : n;
-  }
-};
-
-// A buffer that writes to an output iterator when flushed.
-template <typename OutputIt, typename T, typename Traits = buffer_traits>
-class iterator_buffer : public Traits, public buffer<T> {
- private:
-  OutputIt out_;
-  enum { buffer_size = 256 };
-  T data_[buffer_size];
-
-  static FMT_CONSTEXPR void grow(buffer<T>& buf, size_t) {
-    if (buf.size() == buffer_size) static_cast<iterator_buffer&>(buf).flush();
-  }
-
-  void flush() {
-    auto size = this->size();
-    this->clear();
-    const T* begin = data_;
-    const T* end = begin + this->limit(size);
-    while (begin != end) *out_++ = *begin++;
-  }
-
- public:
-  explicit iterator_buffer(OutputIt out, size_t n = buffer_size)
-      : Traits(n), buffer<T>(grow, data_, 0, buffer_size), out_(out) {}
-  iterator_buffer(iterator_buffer&& other) noexcept
-      : Traits(other),
-        buffer<T>(grow, data_, 0, buffer_size),
-        out_(other.out_) {}
-  ~iterator_buffer() {
-    // Don't crash if flush fails during unwinding.
-    FMT_TRY { flush(); }
-    FMT_CATCH(...) {}
-  }
-
-  auto out() -> OutputIt {
-    flush();
-    return out_;
-  }
-  auto count() const -> size_t { return Traits::count() + this->size(); }
-};
-
-template <typename T>
-class iterator_buffer<T*, T, fixed_buffer_traits> : public fixed_buffer_traits,
-                                                    public buffer<T> {
- private:
-  T* out_;
-  enum { buffer_size = 256 };
-  T data_[buffer_size];
-
-  static FMT_CONSTEXPR void grow(buffer<T>& buf, size_t) {
-    if (buf.size() == buf.capacity())
-      static_cast<iterator_buffer&>(buf).flush();
-  }
-
-  void flush() {
-    size_t n = this->limit(this->size());
-    if (this->data() == out_) {
-      out_ += n;
-      this->set(data_, buffer_size);
-    }
-    this->clear();
-  }
-
- public:
-  explicit iterator_buffer(T* out, size_t n = buffer_size)
-      : fixed_buffer_traits(n), buffer<T>(grow, out, 0, n), out_(out) {}
-  iterator_buffer(iterator_buffer&& other) noexcept
-      : fixed_buffer_traits(other),
-        buffer<T>(static_cast<iterator_buffer&&>(other)),
-        out_(other.out_) {
-    if (this->data() != out_) {
-      this->set(data_, buffer_size);
-      this->clear();
-    }
-  }
-  ~iterator_buffer() { flush(); }
-
-  auto out() -> T* {
-    flush();
-    return out_;
-  }
-  auto count() const -> size_t {
-    return fixed_buffer_traits::count() + this->size();
-  }
-};
-
-template <typename T> class iterator_buffer<T*, T> : public buffer<T> {
- public:
-  explicit iterator_buffer(T* out, size_t = 0)
-      : buffer<T>([](buffer<T>&, size_t) {}, out, 0, ~size_t()) {}
+// An argument reference.
+template <typename Char> union arg_ref {
+  FMT_CONSTEXPR arg_ref(int idx = 0) : index(idx) {}
+  FMT_CONSTEXPR arg_ref(basic_string_view<Char> n) : name(n) {}
 
-  auto out() -> T* { return &*this->end(); }
+  int index;
+  basic_string_view<Char> name;
 };
 
-// A buffer that writes to a container with the contiguous storage.
-template <typename OutputIt>
-class iterator_buffer<
-    OutputIt,
-    enable_if_t<detail::is_back_insert_iterator<OutputIt>::value &&
-                    is_contiguous<typename OutputIt::container_type>::value,
-                typename OutputIt::container_type::value_type>>
-    : public buffer<typename OutputIt::container_type::value_type> {
- private:
-  using container_type = typename OutputIt::container_type;
-  using value_type = typename container_type::value_type;
-  container_type& container_;
-
-  static FMT_CONSTEXPR void grow(buffer<value_type>& buf, size_t capacity) {
-    auto& self = static_cast<iterator_buffer&>(buf);
-    self.container_.resize(capacity);
-    self.set(&self.container_[0], capacity);
-  }
-
- public:
-  explicit iterator_buffer(container_type& c)
-      : buffer<value_type>(grow, c.size()), container_(c) {}
-  explicit iterator_buffer(OutputIt out, size_t = 0)
-      : iterator_buffer(get_container(out)) {}
-
-  auto out() -> OutputIt { return back_inserter(container_); }
+// Format specifiers with width and precision resolved at formatting rather
+// than parsing time to allow reusing the same parsed specifiers with
+// different sets of arguments (precompilation of format strings).
+template <typename Char = char> struct dynamic_format_specs : format_specs {
+  arg_ref<Char> width_ref;
+  arg_ref<Char> precision_ref;
 };
 
-// A buffer that counts the number of code units written discarding the output.
-template <typename T = char> class counting_buffer : public buffer<T> {
- private:
-  enum { buffer_size = 256 };
-  T data_[buffer_size];
-  size_t count_ = 0;
-
-  static FMT_CONSTEXPR void grow(buffer<T>& buf, size_t) {
-    if (buf.size() != buffer_size) return;
-    static_cast<counting_buffer&>(buf).count_ += buf.size();
-    buf.clear();
-  }
-
- public:
-  counting_buffer() : buffer<T>(grow, data_, 0, buffer_size) {}
-
-  auto count() -> size_t { return count_ + this->size(); }
-};
-}  // namespace detail
+// Converts a character to ASCII. Returns '\0' on conversion failure.
+template <typename Char, FMT_ENABLE_IF(std::is_integral<Char>::value)>
+constexpr auto to_ascii(Char c) -> char {
+  return c <= 0xff ? static_cast<char>(c) : '\0';
+}
 
+// Returns the number of code units in a code point or 1 on error.
 template <typename Char>
-FMT_CONSTEXPR void basic_format_parse_context<Char>::do_check_arg_id(int id) {
-  // Argument id is only checked at compile-time during parsing because
-  // formatting has its own validation.
-  if (detail::is_constant_evaluated() &&
-      (!FMT_GCC_VERSION || FMT_GCC_VERSION >= 1200)) {
-    using context = detail::compile_parse_context<Char>;
-    if (id >= static_cast<context*>(this)->num_args())
-      report_error("argument not found");
-  }
+FMT_CONSTEXPR auto code_point_length(const Char* begin) -> int {
+  if (const_check(sizeof(Char) != 1)) return 1;
+  auto c = static_cast<unsigned char>(*begin);
+  return static_cast<int>((0x3a55000000000000ull >> (2 * (c >> 3))) & 3) + 1;
 }
 
+// Parses the range [begin, end) as an unsigned integer. This function assumes
+// that the range is non-empty and the first character is a digit.
 template <typename Char>
-FMT_CONSTEXPR void basic_format_parse_context<Char>::check_dynamic_spec(
-    int arg_id) {
-  if (detail::is_constant_evaluated() &&
-      (!FMT_GCC_VERSION || FMT_GCC_VERSION >= 1200)) {
-    using context = detail::compile_parse_context<Char>;
-    static_cast<context*>(this)->check_dynamic_spec(arg_id);
-  }
+FMT_CONSTEXPR auto parse_nonnegative_int(const Char*& begin, const Char* end,
+                                         int error_value) noexcept -> int {
+  FMT_ASSERT(begin != end && '0' <= *begin && *begin <= '9', "");
+  unsigned value = 0, prev = 0;
+  auto p = begin;
+  do {
+    prev = value;
+    value = value * 10 + unsigned(*p - '0');
+    ++p;
+  } while (p != end && '0' <= *p && *p <= '9');
+  auto num_digits = p - begin;
+  begin = p;
+  int digits10 = static_cast<int>(sizeof(int) * CHAR_BIT * 3 / 10);
+  if (num_digits <= digits10) return static_cast<int>(value);
+  // Check for overflow.
+  unsigned max = INT_MAX;
+  return num_digits == digits10 + 1 &&
+                 prev * 10ull + unsigned(p[-1] - '0') <= max
+             ? static_cast<int>(value)
+             : error_value;
 }
 
-FMT_EXPORT template <typename Context> class basic_format_arg;
-FMT_EXPORT template <typename Context> class basic_format_args;
-FMT_EXPORT template <typename Context> class dynamic_format_arg_store;
-
-// A formatter for objects of type T.
-FMT_EXPORT
-template <typename T, typename Char = char, typename Enable = void>
-struct formatter {
-  // A deleted default constructor indicates a disabled formatter.
-  formatter() = delete;
-};
-
-// Specifies if T has an enabled formatter specialization. A type can be
-// formattable even if it doesn't have a formatter e.g. via a conversion.
-template <typename T, typename Context>
-using has_formatter =
-    std::is_constructible<typename Context::template formatter_type<T>>;
-
-// An output iterator that appends to a buffer. It is used instead of
-// back_insert_iterator to reduce symbol sizes and avoid <iterator> dependency.
-template <typename T> class basic_appender {
- private:
-  detail::buffer<T>* buffer_;
-
-  friend auto get_container(basic_appender app) -> detail::buffer<T>& {
-    return *app.buffer_;
-  }
-
- public:
-  using iterator_category = int;
-  using value_type = T;
-  using difference_type = ptrdiff_t;
-  using pointer = T*;
-  using reference = T&;
-  FMT_UNCHECKED_ITERATOR(basic_appender);
-
-  FMT_CONSTEXPR basic_appender(detail::buffer<T>& buf) : buffer_(&buf) {}
-
-  auto operator=(T c) -> basic_appender& {
-    buffer_->push_back(c);
-    return *this;
+FMT_CONSTEXPR inline auto parse_align(char c) -> align {
+  switch (c) {
+  case '<': return align::left;
+  case '>': return align::right;
+  case '^': return align::center;
   }
-  auto operator*() -> basic_appender& { return *this; }
-  auto operator++() -> basic_appender& { return *this; }
-  auto operator++(int) -> basic_appender { return *this; }
-};
-
-using appender = basic_appender<char>;
-
-namespace detail {
-
-template <typename T, typename Enable = void>
-struct locking : std::true_type {};
-template <typename T>
-struct locking<T, void_t<typename formatter<remove_cvref_t<T>>::nonlocking>>
-    : std::false_type {};
-
-template <typename T = int> FMT_CONSTEXPR inline auto is_locking() -> bool {
-  return locking<T>::value;
-}
-template <typename T1, typename T2, typename... Tail>
-FMT_CONSTEXPR inline auto is_locking() -> bool {
-  return locking<T1>::value || is_locking<T2, Tail...>();
-}
-
-// An optimized version of std::copy with the output value type (T).
-template <typename T, typename InputIt>
-auto copy(InputIt begin, InputIt end, appender out) -> appender {
-  get_container(out).append(begin, end);
-  return out;
-}
-
-template <typename T, typename InputIt, typename OutputIt,
-          FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value)>
-auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
-  get_container(out).append(begin, end);
-  return out;
-}
-
-template <typename T, typename InputIt, typename OutputIt,
-          FMT_ENABLE_IF(!is_back_insert_iterator<OutputIt>::value)>
-FMT_CONSTEXPR auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
-  while (begin != end) *out++ = static_cast<T>(*begin++);
-  return out;
-}
-
-template <typename T>
-FMT_CONSTEXPR auto copy(const T* begin, const T* end, T* out) -> T* {
-  if (is_constant_evaluated()) return copy<T, const T*, T*>(begin, end, out);
-  auto size = to_unsigned(end - begin);
-  if (size > 0) memcpy(out, begin, size * sizeof(T));
-  return out + size;
-}
-
-template <typename T, typename V, typename OutputIt>
-FMT_CONSTEXPR auto copy(basic_string_view<V> s, OutputIt out) -> OutputIt {
-  return copy<T>(s.begin(), s.end(), out);
-}
-
-template <typename Context, typename T>
-constexpr auto has_const_formatter_impl(T*)
-    -> decltype(typename Context::template formatter_type<T>().format(
-                    std::declval<const T&>(), std::declval<Context&>()),
-                true) {
-  return true;
-}
-template <typename Context>
-constexpr auto has_const_formatter_impl(...) -> bool {
-  return false;
-}
-template <typename T, typename Context>
-constexpr auto has_const_formatter() -> bool {
-  return has_const_formatter_impl<Context>(static_cast<T*>(nullptr));
-}
-
-// Maps an output iterator to a buffer.
-template <typename T, typename OutputIt>
-auto get_buffer(OutputIt out) -> iterator_buffer<OutputIt, T> {
-  return iterator_buffer<OutputIt, T>(out);
-}
-template <typename T> auto get_buffer(basic_appender<T> out) -> buffer<T>& {
-  return get_container(out);
-}
-
-template <typename Buf, typename OutputIt>
-auto get_iterator(Buf& buf, OutputIt) -> decltype(buf.out()) {
-  return buf.out();
-}
-template <typename T, typename OutputIt>
-auto get_iterator(buffer<T>&, OutputIt out) -> OutputIt {
-  return out;
-}
-
-struct view {};
-
-template <typename Char, typename T> struct named_arg : view {
-  const Char* name;
-  const T& value;
-  named_arg(const Char* n, const T& v) : name(n), value(v) {}
-};
-
-template <typename Char> struct named_arg_info {
-  const Char* name;
-  int id;
-};
-
-template <typename T> struct is_named_arg : std::false_type {};
-template <typename T> struct is_statically_named_arg : std::false_type {};
-
-template <typename T, typename Char>
-struct is_named_arg<named_arg<Char, T>> : std::true_type {};
-
-template <bool B = false> constexpr auto count() -> size_t { return B ? 1 : 0; }
-template <bool B1, bool B2, bool... Tail> constexpr auto count() -> size_t {
-  return (B1 ? 1 : 0) + count<B2, Tail...>();
-}
-
-template <typename... Args> constexpr auto count_named_args() -> size_t {
-  return count<is_named_arg<Args>::value...>();
+  return align::none;
 }
 
-template <typename... Args>
-constexpr auto count_statically_named_args() -> size_t {
-  return count<is_statically_named_arg<Args>::value...>();
+template <typename Char> constexpr auto is_name_start(Char c) -> bool {
+  return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || c == '_';
 }
 
-struct unformattable {};
-struct unformattable_char : unformattable {};
-struct unformattable_pointer : unformattable {};
-
-template <typename Char> struct string_value {
-  const Char* data;
-  size_t size;
-};
-
-template <typename Char> struct named_arg_value {
-  const named_arg_info<Char>* data;
-  size_t size;
-};
-
-template <typename Context> struct custom_value {
-  using parse_context = typename Context::parse_context_type;
-  void* value;
-  void (*format)(void* arg, parse_context& parse_ctx, Context& ctx);
-};
-
-// A formatting argument value.
-template <typename Context> class value {
- public:
-  using char_type = typename Context::char_type;
-
-  union {
-    monostate no_value;
-    int int_value;
-    unsigned uint_value;
-    long long long_long_value;
-    unsigned long long ulong_long_value;
-    int128_opt int128_value;
-    uint128_opt uint128_value;
-    bool bool_value;
-    char_type char_value;
-    float float_value;
-    double double_value;
-    long double long_double_value;
-    const void* pointer;
-    string_value<char_type> string;
-    custom_value<Context> custom;
-    named_arg_value<char_type> named_args;
-  };
-
-  constexpr FMT_ALWAYS_INLINE value() : no_value() {}
-  constexpr FMT_ALWAYS_INLINE value(int val) : int_value(val) {}
-  constexpr FMT_ALWAYS_INLINE value(unsigned val) : uint_value(val) {}
-  constexpr FMT_ALWAYS_INLINE value(long long val) : long_long_value(val) {}
-  constexpr FMT_ALWAYS_INLINE value(unsigned long long val)
-      : ulong_long_value(val) {}
-  FMT_ALWAYS_INLINE value(int128_opt val) : int128_value(val) {}
-  FMT_ALWAYS_INLINE value(uint128_opt val) : uint128_value(val) {}
-  constexpr FMT_ALWAYS_INLINE value(float val) : float_value(val) {}
-  constexpr FMT_ALWAYS_INLINE value(double val) : double_value(val) {}
-  FMT_ALWAYS_INLINE value(long double val) : long_double_value(val) {}
-  constexpr FMT_ALWAYS_INLINE value(bool val) : bool_value(val) {}
-  constexpr FMT_ALWAYS_INLINE value(char_type val) : char_value(val) {}
-  FMT_CONSTEXPR FMT_ALWAYS_INLINE value(const char_type* val) {
-    string.data = val;
-    if (is_constant_evaluated()) string.size = {};
-  }
-  FMT_CONSTEXPR FMT_ALWAYS_INLINE value(basic_string_view<char_type> val) {
-    string.data = val.data();
-    string.size = val.size();
-  }
-  FMT_ALWAYS_INLINE value(const void* val) : pointer(val) {}
-  FMT_ALWAYS_INLINE value(const named_arg_info<char_type>* args, size_t size)
-      : named_args{args, size} {}
-
-  template <typename T> FMT_CONSTEXPR20 FMT_ALWAYS_INLINE value(T& val) {
-    using value_type = remove_const_t<T>;
-    // T may overload operator& e.g. std::vector<bool>::reference in libc++.
-#if defined(__cpp_if_constexpr)
-    if constexpr (std::is_same<decltype(&val), T*>::value)
-      custom.value = const_cast<value_type*>(&val);
-#endif
-    if (!is_constant_evaluated())
-      custom.value = const_cast<char*>(&reinterpret_cast<const char&>(val));
-    // Get the formatter type through the context to allow different contexts
-    // have different extension points, e.g. `formatter<T>` for `format` and
-    // `printf_formatter<T>` for `printf`.
-    custom.format = format_custom_arg<
-        value_type, typename Context::template formatter_type<value_type>>;
-  }
-  value(unformattable);
-  value(unformattable_char);
-  value(unformattable_pointer);
-
- private:
-  // Formats an argument of a custom type, such as a user-defined class.
-  template <typename T, typename Formatter>
-  static void format_custom_arg(void* arg,
-                                typename Context::parse_context_type& parse_ctx,
-                                Context& ctx) {
-    auto f = Formatter();
-    parse_ctx.advance_to(f.parse(parse_ctx));
-    using qualified_type =
-        conditional_t<has_const_formatter<T, Context>(), const T, T>;
-    // format must be const for compatibility with std::format and compilation.
-    const auto& cf = f;
-    ctx.advance_to(cf.format(*static_cast<qualified_type*>(arg), ctx));
+template <typename Char, typename Handler>
+FMT_CONSTEXPR auto parse_arg_id(const Char* begin, const Char* end,
+                                Handler&& handler) -> const Char* {
+  Char c = *begin;
+  if (c >= '0' && c <= '9') {
+    int index = 0;
+    if (c != '0')
+      index = parse_nonnegative_int(begin, end, INT_MAX);
+    else
+      ++begin;
+    if (begin == end || (*begin != '}' && *begin != ':'))
+      report_error("invalid format string");
+    else
+      handler.on_index(index);
+    return begin;
   }
-};
-
-// To minimize the number of types we need to deal with, long is translated
-// either to int or to long long depending on its size.
-enum { long_short = sizeof(long) == sizeof(int) };
-using long_type = conditional_t<long_short, int, long long>;
-using ulong_type = conditional_t<long_short, unsigned, unsigned long long>;
-
-template <typename T> struct format_as_result {
-  template <typename U,
-            FMT_ENABLE_IF(std::is_enum<U>::value || std::is_class<U>::value)>
-  static auto map(U*) -> remove_cvref_t<decltype(format_as(std::declval<U>()))>;
-  static auto map(...) -> void;
-
-  using type = decltype(map(static_cast<T*>(nullptr)));
-};
-template <typename T> using format_as_t = typename format_as_result<T>::type;
-
-template <typename T>
-struct has_format_as
-    : bool_constant<!std::is_same<format_as_t<T>, void>::value> {};
-
-#define FMT_MAP_API FMT_CONSTEXPR FMT_ALWAYS_INLINE
-
-// Maps formatting arguments to core types.
-// arg_mapper reports errors by returning unformattable instead of using
-// static_assert because it's used in the is_formattable trait.
-template <typename Context> struct arg_mapper {
-  using char_type = typename Context::char_type;
-
-  FMT_MAP_API auto map(signed char val) -> int { return val; }
-  FMT_MAP_API auto map(unsigned char val) -> unsigned { return val; }
-  FMT_MAP_API auto map(short val) -> int { return val; }
-  FMT_MAP_API auto map(unsigned short val) -> unsigned { return val; }
-  FMT_MAP_API auto map(int val) -> int { return val; }
-  FMT_MAP_API auto map(unsigned val) -> unsigned { return val; }
-  FMT_MAP_API auto map(long val) -> long_type { return val; }
-  FMT_MAP_API auto map(unsigned long val) -> ulong_type { return val; }
-  FMT_MAP_API auto map(long long val) -> long long { return val; }
-  FMT_MAP_API auto map(unsigned long long val) -> unsigned long long {
-    return val;
-  }
-  FMT_MAP_API auto map(int128_opt val) -> int128_opt { return val; }
-  FMT_MAP_API auto map(uint128_opt val) -> uint128_opt { return val; }
-  FMT_MAP_API auto map(bool val) -> bool { return val; }
-
-  template <typename T, FMT_ENABLE_IF(std::is_same<T, char>::value ||
-                                      std::is_same<T, char_type>::value)>
-  FMT_MAP_API auto map(T val) -> char_type {
-    return val;
-  }
-  template <typename T, enable_if_t<(std::is_same<T, wchar_t>::value ||
-#ifdef __cpp_char8_t
-                                     std::is_same<T, char8_t>::value ||
-#endif
-                                     std::is_same<T, char16_t>::value ||
-                                     std::is_same<T, char32_t>::value) &&
-                                        !std::is_same<T, char_type>::value,
-                                    int> = 0>
-  FMT_MAP_API auto map(T) -> unformattable_char {
-    return {};
-  }
-
-  FMT_MAP_API auto map(float val) -> float { return val; }
-  FMT_MAP_API auto map(double val) -> double { return val; }
-  FMT_MAP_API auto map(long double val) -> long double { return val; }
-
-  FMT_MAP_API auto map(char_type* val) -> const char_type* { return val; }
-  FMT_MAP_API auto map(const char_type* val) -> const char_type* { return val; }
-  template <typename T, typename Char = char_t<T>,
-            FMT_ENABLE_IF(std::is_same<Char, char_type>::value &&
-                          !std::is_pointer<T>::value)>
-  FMT_MAP_API auto map(const T& val) -> basic_string_view<Char> {
-    return to_string_view(val);
-  }
-  template <typename T, typename Char = char_t<T>,
-            FMT_ENABLE_IF(!std::is_same<Char, char_type>::value &&
-                          !std::is_pointer<T>::value)>
-  FMT_MAP_API auto map(const T&) -> unformattable_char {
-    return {};
-  }
-
-  FMT_MAP_API auto map(void* val) -> const void* { return val; }
-  FMT_MAP_API auto map(const void* val) -> const void* { return val; }
-  FMT_MAP_API auto map(std::nullptr_t val) -> const void* { return val; }
-
-  // Use SFINAE instead of a const T* parameter to avoid a conflict with the
-  // array overload.
-  template <
-      typename T,
-      FMT_ENABLE_IF(
-          std::is_pointer<T>::value || std::is_member_pointer<T>::value ||
-          std::is_function<typename std::remove_pointer<T>::type>::value ||
-          (std::is_array<T>::value &&
-           !std::is_convertible<T, const char_type*>::value))>
-  FMT_CONSTEXPR auto map(const T&) -> unformattable_pointer {
-    return {};
-  }
-
-  template <typename T, std::size_t N,
-            FMT_ENABLE_IF(!std::is_same<T, wchar_t>::value)>
-  FMT_MAP_API auto map(const T (&values)[N]) -> const T (&)[N] {
-    return values;
-  }
-
-  // Only map owning types because mapping views can be unsafe.
-  template <typename T, typename U = format_as_t<T>,
-            FMT_ENABLE_IF(std::is_arithmetic<U>::value)>
-  FMT_MAP_API auto map(const T& val) -> decltype(FMT_DECLTYPE_THIS map(U())) {
-    return map(format_as(val));
-  }
-
-  template <typename T, typename U = remove_const_t<T>>
-  struct formattable : bool_constant<has_const_formatter<U, Context>() ||
-                                     (has_formatter<U, Context>::value &&
-                                      !std::is_const<T>::value)> {};
-
-  template <typename T, FMT_ENABLE_IF(formattable<T>::value)>
-  FMT_MAP_API auto do_map(T& val) -> T& {
-    return val;
-  }
-  template <typename T, FMT_ENABLE_IF(!formattable<T>::value)>
-  FMT_MAP_API auto do_map(T&) -> unformattable {
-    return {};
-  }
-
-  // is_fundamental is used to allow formatters for extended FP types.
-  template <typename T, typename U = remove_const_t<T>,
-            FMT_ENABLE_IF(
-                (std::is_class<U>::value || std::is_enum<U>::value ||
-                 std::is_union<U>::value || std::is_fundamental<U>::value) &&
-                !has_to_string_view<U>::value && !is_char<U>::value &&
-                !is_named_arg<U>::value && !std::is_integral<U>::value &&
-                !std::is_arithmetic<format_as_t<U>>::value)>
-  FMT_MAP_API auto map(T& val) -> decltype(FMT_DECLTYPE_THIS do_map(val)) {
-    return do_map(val);
+  if (FMT_OPTIMIZE_SIZE > 1 || !is_name_start(c)) {
+    report_error("invalid format string");
+    return begin;
   }
+  auto it = begin;
+  do {
+    ++it;
+  } while (it != end && (is_name_start(*it) || ('0' <= *it && *it <= '9')));
+  handler.on_name({begin, to_unsigned(it - begin)});
+  return it;
+}
+
+template <typename Char> struct dynamic_spec_handler {
+  parse_context<Char>& ctx;
+  arg_ref<Char>& ref;
+  arg_id_kind& kind;
 
-  template <typename T, FMT_ENABLE_IF(is_named_arg<T>::value)>
-  FMT_MAP_API auto map(const T& named_arg)
-      -> decltype(FMT_DECLTYPE_THIS map(named_arg.value)) {
-    return map(named_arg.value);
+  FMT_CONSTEXPR void on_index(int id) {
+    ref = id;
+    kind = arg_id_kind::index;
+    ctx.check_arg_id(id);
+    ctx.check_dynamic_spec(id);
+  }
+  FMT_CONSTEXPR void on_name(basic_string_view<Char> id) {
+    ref = id;
+    kind = arg_id_kind::name;
+    ctx.check_arg_id(id);
   }
-
-  auto map(...) -> unformattable { return {}; }
 };
 
-// A type constant after applying arg_mapper<Context>.
-template <typename T, typename Context>
-using mapped_type_constant =
-    type_constant<decltype(arg_mapper<Context>().map(std::declval<const T&>())),
-                  typename Context::char_type>;
-
-enum { packed_arg_bits = 4 };
-// Maximum number of arguments with packed types.
-enum { max_packed_args = 62 / packed_arg_bits };
-enum : unsigned long long { is_unpacked_bit = 1ULL << 63 };
-enum : unsigned long long { has_named_args_bit = 1ULL << 62 };
-
-template <typename It, typename T, typename Enable = void>
-struct is_output_iterator : std::false_type {};
-
-template <> struct is_output_iterator<appender, char> : std::true_type {};
-
-template <typename It, typename T>
-struct is_output_iterator<
-    It, T, void_t<decltype(*std::declval<It&>()++ = std::declval<T>())>>
-    : std::true_type {};
-
-// A type-erased reference to an std::locale to avoid a heavy <locale> include.
-class locale_ref {
- private:
-  const void* locale_;  // A type-erased pointer to std::locale.
-
- public:
-  constexpr locale_ref() : locale_(nullptr) {}
-  template <typename Locale> explicit locale_ref(const Locale& loc);
-
-  explicit operator bool() const noexcept { return locale_ != nullptr; }
-
-  template <typename Locale> auto get() const -> Locale;
+template <typename Char> struct parse_dynamic_spec_result {
+  const Char* end;
+  arg_id_kind kind;
 };
 
-template <typename> constexpr auto encode_types() -> unsigned long long {
-  return 0;
+// Parses integer | "{" [arg_id] "}".
+template <typename Char>
+FMT_CONSTEXPR auto parse_dynamic_spec(const Char* begin, const Char* end,
+                                      int& value, arg_ref<Char>& ref,
+                                      parse_context<Char>& ctx)
+    -> parse_dynamic_spec_result<Char> {
+  FMT_ASSERT(begin != end, "");
+  auto kind = arg_id_kind::none;
+  if ('0' <= *begin && *begin <= '9') {
+    int val = parse_nonnegative_int(begin, end, -1);
+    if (val == -1) report_error("number is too big");
+    value = val;
+  } else {
+    if (*begin == '{') {
+      ++begin;
+      if (begin != end) {
+        Char c = *begin;
+        if (c == '}' || c == ':') {
+          int id = ctx.next_arg_id();
+          ref = id;
+          kind = arg_id_kind::index;
+          ctx.check_dynamic_spec(id);
+        } else {
+          begin = parse_arg_id(begin, end,
+                               dynamic_spec_handler<Char>{ctx, ref, kind});
+        }
+      }
+      if (begin != end && *begin == '}') return {++begin, kind};
+    }
+    report_error("invalid format string");
+  }
+  return {begin, kind};
 }
 
-template <typename Context, typename Arg, typename... Args>
-constexpr auto encode_types() -> unsigned long long {
-  return static_cast<unsigned>(mapped_type_constant<Arg, Context>::value) |
-         (encode_types<Context, Args...>() << packed_arg_bits);
+template <typename Char>
+FMT_CONSTEXPR auto parse_width(const Char* begin, const Char* end,
+                               format_specs& specs, arg_ref<Char>& width_ref,
+                               parse_context<Char>& ctx) -> const Char* {
+  auto result = parse_dynamic_spec(begin, end, specs.width, width_ref, ctx);
+  specs.set_dynamic_width(result.kind);
+  return result.end;
 }
 
-template <typename Context, typename... T, size_t NUM_ARGS = sizeof...(T)>
-constexpr unsigned long long make_descriptor() {
-  return NUM_ARGS <= max_packed_args ? encode_types<Context, T...>()
-                                     : is_unpacked_bit | NUM_ARGS;
+template <typename Char>
+FMT_CONSTEXPR auto parse_precision(const Char* begin, const Char* end,
+                                   format_specs& specs,
+                                   arg_ref<Char>& precision_ref,
+                                   parse_context<Char>& ctx) -> const Char* {
+  ++begin;
+  if (begin == end) {
+    report_error("invalid precision");
+    return begin;
+  }
+  auto result =
+      parse_dynamic_spec(begin, end, specs.precision, precision_ref, ctx);
+  specs.set_dynamic_precision(result.kind);
+  return result.end;
 }
 
-// This type is intentionally undefined, only used for errors.
-template <typename T, typename Char>
-#if FMT_CLANG_VERSION && FMT_CLANG_VERSION <= 1500
-// https://github.com/fmtlib/fmt/issues/3796
-struct type_is_unformattable_for {
-};
-#else
-struct type_is_unformattable_for;
-#endif
+enum class state { start, align, sign, hash, zero, width, precision, locale };
 
-template <bool PACKED, typename Context, typename T, FMT_ENABLE_IF(PACKED)>
-FMT_CONSTEXPR auto make_arg(T& val) -> value<Context> {
-  using arg_type = remove_cvref_t<decltype(arg_mapper<Context>().map(val))>;
+// Parses standard format specifiers.
+template <typename Char>
+FMT_CONSTEXPR auto parse_format_specs(const Char* begin, const Char* end,
+                                      dynamic_format_specs<Char>& specs,
+                                      parse_context<Char>& ctx, type arg_type)
+    -> const Char* {
+  auto c = '\0';
+  if (end - begin > 1) {
+    auto next = to_ascii(begin[1]);
+    c = parse_align(next) == align::none ? to_ascii(*begin) : '\0';
+  } else {
+    if (begin == end) return begin;
+    c = to_ascii(*begin);
+  }
 
-  // Use enum instead of constexpr because the latter may generate code.
-  enum {
-    formattable_char = !std::is_same<arg_type, unformattable_char>::value
-  };
-  static_assert(formattable_char, "Mixing character types is disallowed.");
+  struct {
+    state current_state = state::start;
+    FMT_CONSTEXPR void operator()(state s, bool valid = true) {
+      if (current_state >= s || !valid)
+        report_error("invalid format specifier");
+      current_state = s;
+    }
+  } enter_state;
 
-  // Formatting of arbitrary pointers is disallowed. If you want to format a
-  // pointer cast it to `void*` or `const void*`. In particular, this forbids
-  // formatting of `[const] volatile char*` printed as bool by iostreams.
-  enum {
-    formattable_pointer = !std::is_same<arg_type, unformattable_pointer>::value
-  };
-  static_assert(formattable_pointer,
-                "Formatting of non-void pointers is disallowed.");
+  using pres = presentation_type;
+  constexpr auto integral_set = sint_set | uint_set | bool_set | char_set;
+  struct {
+    const Char*& begin;
+    format_specs& specs;
+    type arg_type;
 
-  enum { formattable = !std::is_same<arg_type, unformattable>::value };
-#if defined(__cpp_if_constexpr)
-  if constexpr (!formattable)
-    type_is_unformattable_for<T, typename Context::char_type> _;
-#endif
-  static_assert(
-      formattable,
-      "Cannot format an argument. To make type T formattable provide a "
-      "formatter<T> specialization: https://fmt.dev/latest/api.html#udt");
-  return {arg_mapper<Context>().map(val)};
-}
+    FMT_CONSTEXPR auto operator()(pres pres_type, int set) -> const Char* {
+      if (!in(arg_type, set)) report_error("invalid format specifier");
+      specs.set_type(pres_type);
+      return begin + 1;
+    }
+  } parse_presentation_type{begin, specs, arg_type};
 
-template <typename Context, typename T>
-FMT_CONSTEXPR auto make_arg(T& val) -> basic_format_arg<Context> {
-  auto arg = basic_format_arg<Context>();
-  arg.type_ = mapped_type_constant<T, Context>::value;
-  arg.value_ = make_arg<true, Context>(val);
-  return arg;
+  for (;;) {
+    switch (c) {
+    case '<':
+    case '>':
+    case '^':
+      enter_state(state::align);
+      specs.set_align(parse_align(c));
+      ++begin;
+      break;
+    case '+':
+    case ' ':
+      specs.set_sign(c == ' ' ? sign::space : sign::plus);
+      FMT_FALLTHROUGH;
+    case '-':
+      enter_state(state::sign, in(arg_type, sint_set | float_set));
+      ++begin;
+      break;
+    case '#':
+      enter_state(state::hash, is_arithmetic_type(arg_type));
+      specs.set_alt();
+      ++begin;
+      break;
+    case '0':
+      enter_state(state::zero);
+      if (!is_arithmetic_type(arg_type))
+        report_error("format specifier requires numeric argument");
+      if (specs.align() == align::none) {
+        // Ignore 0 if align is specified for compatibility with std::format.
+        specs.set_align(align::numeric);
+        specs.set_fill('0');
+      }
+      ++begin;
+      break;
+      // clang-format off
+    case '1': case '2': case '3': case '4': case '5':
+    case '6': case '7': case '8': case '9': case '{':
+      // clang-format on
+      enter_state(state::width);
+      begin = parse_width(begin, end, specs, specs.width_ref, ctx);
+      break;
+    case '.':
+      enter_state(state::precision,
+                  in(arg_type, float_set | string_set | cstring_set));
+      begin = parse_precision(begin, end, specs, specs.precision_ref, ctx);
+      break;
+    case 'L':
+      enter_state(state::locale, is_arithmetic_type(arg_type));
+      specs.set_localized();
+      ++begin;
+      break;
+    case 'd': return parse_presentation_type(pres::dec, integral_set);
+    case 'X': specs.set_upper(); FMT_FALLTHROUGH;
+    case 'x': return parse_presentation_type(pres::hex, integral_set);
+    case 'o': return parse_presentation_type(pres::oct, integral_set);
+    case 'B': specs.set_upper(); FMT_FALLTHROUGH;
+    case 'b': return parse_presentation_type(pres::bin, integral_set);
+    case 'E': specs.set_upper(); FMT_FALLTHROUGH;
+    case 'e': return parse_presentation_type(pres::exp, float_set);
+    case 'F': specs.set_upper(); FMT_FALLTHROUGH;
+    case 'f': return parse_presentation_type(pres::fixed, float_set);
+    case 'G': specs.set_upper(); FMT_FALLTHROUGH;
+    case 'g': return parse_presentation_type(pres::general, float_set);
+    case 'A': specs.set_upper(); FMT_FALLTHROUGH;
+    case 'a': return parse_presentation_type(pres::hexfloat, float_set);
+    case 'c':
+      if (arg_type == type::bool_type) report_error("invalid format specifier");
+      return parse_presentation_type(pres::chr, integral_set);
+    case 's':
+      return parse_presentation_type(pres::string,
+                                     bool_set | string_set | cstring_set);
+    case 'p':
+      return parse_presentation_type(pres::pointer, pointer_set | cstring_set);
+    case '?':
+      return parse_presentation_type(pres::debug,
+                                     char_set | string_set | cstring_set);
+    case '}': return begin;
+    default:  {
+      if (*begin == '}') return begin;
+      // Parse fill and alignment.
+      auto fill_end = begin + code_point_length(begin);
+      if (end - fill_end <= 0) {
+        report_error("invalid format specifier");
+        return begin;
+      }
+      if (*begin == '{') {
+        report_error("invalid fill character '{'");
+        return begin;
+      }
+      auto alignment = parse_align(to_ascii(*fill_end));
+      enter_state(state::align, alignment != align::none);
+      specs.set_fill(
+          basic_string_view<Char>(begin, to_unsigned(fill_end - begin)));
+      specs.set_align(alignment);
+      begin = fill_end + 1;
+    }
+    }
+    if (begin == end) return begin;
+    c = to_ascii(*begin);
+  }
 }
 
-template <bool PACKED, typename Context, typename T, FMT_ENABLE_IF(!PACKED)>
-FMT_CONSTEXPR inline auto make_arg(T& val) -> basic_format_arg<Context> {
-  return make_arg<Context>(val);
+template <typename Char, typename Handler>
+FMT_CONSTEXPR FMT_INLINE auto parse_replacement_field(const Char* begin,
+                                                      const Char* end,
+                                                      Handler&& handler)
+    -> const Char* {
+  ++begin;
+  if (begin == end) {
+    handler.on_error("invalid format string");
+    return end;
+  }
+  int arg_id = 0;
+  switch (*begin) {
+  case '}':
+    handler.on_replacement_field(handler.on_arg_id(), begin);
+    return begin + 1;
+  case '{': handler.on_text(begin, begin + 1); return begin + 1;
+  case ':': arg_id = handler.on_arg_id(); break;
+  default:  {
+    struct id_adapter {
+      Handler& handler;
+      int arg_id;
+
+      FMT_CONSTEXPR void on_index(int id) { arg_id = handler.on_arg_id(id); }
+      FMT_CONSTEXPR void on_name(basic_string_view<Char> id) {
+        arg_id = handler.on_arg_id(id);
+      }
+    } adapter = {handler, 0};
+    begin = parse_arg_id(begin, end, adapter);
+    arg_id = adapter.arg_id;
+    Char c = begin != end ? *begin : Char();
+    if (c == '}') {
+      handler.on_replacement_field(arg_id, begin);
+      return begin + 1;
+    }
+    if (c != ':') {
+      handler.on_error("missing '}' in format string");
+      return end;
+    }
+    break;
+  }
+  }
+  begin = handler.on_format_specs(arg_id, begin + 1, end);
+  if (begin == end || *begin != '}')
+    return handler.on_error("unknown format specifier"), end;
+  return begin + 1;
 }
 
-template <typename Context, size_t NUM_ARGS>
-using arg_t = conditional_t<NUM_ARGS <= max_packed_args, value<Context>,
-                            basic_format_arg<Context>>;
+template <typename Char, typename Handler>
+FMT_CONSTEXPR void parse_format_string(basic_string_view<Char> fmt,
+                                       Handler&& handler) {
+  auto begin = fmt.data(), end = begin + fmt.size();
+  auto p = begin;
+  while (p != end) {
+    auto c = *p++;
+    if (c == '{') {
+      handler.on_text(begin, p - 1);
+      begin = p = parse_replacement_field(p - 1, end, handler);
+    } else if (c == '}') {
+      if (p == end || *p != '}')
+        return handler.on_error("unmatched '}' in format string");
+      handler.on_text(begin, p);
+      begin = ++p;
+    }
+  }
+  handler.on_text(begin, end);
+}
 
-template <typename Char, typename T, FMT_ENABLE_IF(!is_named_arg<T>::value)>
-void init_named_arg(named_arg_info<Char>*, int& arg_index, int&, const T&) {
-  ++arg_index;
+// Checks char specs and returns true iff the presentation type is char-like.
+FMT_CONSTEXPR inline auto check_char_specs(const format_specs& specs) -> bool {
+  auto type = specs.type();
+  if (type != presentation_type::none && type != presentation_type::chr &&
+      type != presentation_type::debug) {
+    return false;
+  }
+  if (specs.align() == align::numeric || specs.sign() != sign::none ||
+      specs.alt()) {
+    report_error("invalid format specifier for char");
+  }
+  return true;
 }
-template <typename Char, typename T, FMT_ENABLE_IF(is_named_arg<T>::value)>
-void init_named_arg(named_arg_info<Char>* named_args, int& arg_index,
-                    int& named_arg_index, const T& arg) {
-  named_args[named_arg_index++] = {arg.name, arg_index++};
+
+// A base class for compile-time strings.
+struct compile_string {};
+
+template <typename T, typename Char>
+FMT_VISIBILITY("hidden")  // Suppress an ld warning on macOS (#3769).
+FMT_CONSTEXPR auto invoke_parse(parse_context<Char>& ctx) -> const Char* {
+  using mapped_type = remove_cvref_t<mapped_t<T, Char>>;
+  constexpr bool formattable =
+      std::is_constructible<formatter<mapped_type, Char>>::value;
+  if (!formattable) return ctx.begin();  // Error is reported in the value ctor.
+  using formatted_type = conditional_t<formattable, mapped_type, int>;
+  return formatter<formatted_type, Char>().parse(ctx);
 }
 
-// An array of references to arguments. It can be implicitly converted to
-// `fmt::basic_format_args` for passing into type-erased formatting functions
-// such as `fmt::vformat`.
-template <typename Context, size_t NUM_ARGS, size_t NUM_NAMED_ARGS,
-          unsigned long long DESC>
-struct format_arg_store {
-  // args_[0].named_args points to named_args to avoid bloating format_args.
-  // +1 to workaround a bug in gcc 7.5 that causes duplicated-branches warning.
-  static constexpr size_t ARGS_ARR_SIZE = 1 + (NUM_ARGS != 0 ? NUM_ARGS : +1);
+template <typename... T> struct arg_pack {};
+
+template <typename Char, int NUM_ARGS, int NUM_NAMED_ARGS, bool DYNAMIC_NAMES>
+class format_string_checker {
+ private:
+  type types_[max_of<size_t>(1, NUM_ARGS)];
+  named_arg_info<Char> named_args_[max_of<size_t>(1, NUM_NAMED_ARGS)];
+  compile_parse_context<Char> context_;
 
-  arg_t<Context, NUM_ARGS> args[ARGS_ARR_SIZE];
-  named_arg_info<typename Context::char_type> named_args[NUM_NAMED_ARGS];
+  using parse_func = auto (*)(parse_context<Char>&) -> const Char*;
+  parse_func parse_funcs_[max_of<size_t>(1, NUM_ARGS)];
 
+ public:
   template <typename... T>
-  FMT_MAP_API format_arg_store(T&... values)
-      : args{{named_args, NUM_NAMED_ARGS},
-             make_arg<NUM_ARGS <= max_packed_args, Context>(values)...} {
-    using dummy = int[];
+  FMT_CONSTEXPR explicit format_string_checker(basic_string_view<Char> fmt,
+                                               arg_pack<T...>)
+      : types_{mapped_type_constant<T, Char>::value...},
+        named_args_{},
+        context_(fmt, NUM_ARGS, types_),
+        parse_funcs_{&invoke_parse<T, Char>...} {
     int arg_index = 0, named_arg_index = 0;
-    (void)dummy{
-        0,
-        (init_named_arg(named_args, arg_index, named_arg_index, values), 0)...};
+    FMT_APPLY_VARIADIC(
+        init_static_named_arg<T>(named_args_, arg_index, named_arg_index));
+    ignore_unused(arg_index, named_arg_index);
   }
 
-  format_arg_store(format_arg_store&& rhs) {
-    args[0] = {named_args, NUM_NAMED_ARGS};
-    for (size_t i = 1; i < ARGS_ARR_SIZE; ++i) args[i] = rhs.args[i];
-    for (size_t i = 0; i < NUM_NAMED_ARGS; ++i)
-      named_args[i] = rhs.named_args[i];
+  FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
+
+  FMT_CONSTEXPR auto on_arg_id() -> int { return context_.next_arg_id(); }
+  FMT_CONSTEXPR auto on_arg_id(int id) -> int {
+    context_.check_arg_id(id);
+    return id;
+  }
+  FMT_CONSTEXPR auto on_arg_id(basic_string_view<Char> id) -> int {
+    for (int i = 0; i < NUM_NAMED_ARGS; ++i) {
+      if (named_args_[i].name == id) return named_args_[i].id;
+    }
+    if (!DYNAMIC_NAMES) on_error("argument not found");
+    return -1;
   }
 
-  format_arg_store(const format_arg_store& rhs) = delete;
-  format_arg_store& operator=(const format_arg_store& rhs) = delete;
-  format_arg_store& operator=(format_arg_store&& rhs) = delete;
-};
+  FMT_CONSTEXPR void on_replacement_field(int id, const Char* begin) {
+    on_format_specs(id, begin, begin);  // Call parse() on empty specs.
+  }
 
-// A specialization of format_arg_store without named arguments.
-// It is a plain struct to reduce binary size in debug mode.
-template <typename Context, size_t NUM_ARGS, unsigned long long DESC>
-struct format_arg_store<Context, NUM_ARGS, 0, DESC> {
-  // +1 to workaround a bug in gcc 7.5 that causes duplicated-branches warning.
-  arg_t<Context, NUM_ARGS> args[NUM_ARGS != 0 ? NUM_ARGS : +1];
+  FMT_CONSTEXPR auto on_format_specs(int id, const Char* begin, const Char* end)
+      -> const Char* {
+    context_.advance_to(begin);
+    if (id >= 0 && id < NUM_ARGS) return parse_funcs_[id](context_);
+
+    // If id is out of range, it means we do not know the type and cannot parse
+    // the format at compile time. Instead, skip over content until we finish
+    // the format spec, accounting for any nested replacements.
+    for (int bracket_count = 0;
+         begin != end && (bracket_count > 0 || *begin != '}'); ++begin) {
+      if (*begin == '{')
+        ++bracket_count;
+      else if (*begin == '}')
+        --bracket_count;
+    }
+    return begin;
+  }
+
+  FMT_NORETURN FMT_CONSTEXPR void on_error(const char* message) {
+    report_error(message);
+  }
 };
 
-}  // namespace detail
-FMT_BEGIN_EXPORT
+/// A contiguous memory buffer with an optional growing ability. It is an
+/// internal class and shouldn't be used directly, only via `memory_buffer`.
+template <typename T> class buffer {
+ private:
+  T* ptr_;
+  size_t size_;
+  size_t capacity_;
+
+  using grow_fun = void (*)(buffer& buf, size_t capacity);
+  grow_fun grow_;
+
+ protected:
+  // Don't initialize ptr_ since it is not accessed to save a few cycles.
+  FMT_MSC_WARNING(suppress : 26495)
+  FMT_CONSTEXPR buffer(grow_fun grow, size_t sz) noexcept
+      : size_(sz), capacity_(sz), grow_(grow) {}
+
+  constexpr buffer(grow_fun grow, T* p = nullptr, size_t sz = 0,
+                   size_t cap = 0) noexcept
+      : ptr_(p), size_(sz), capacity_(cap), grow_(grow) {}
 
-// A formatting argument. Context is a template parameter for the compiled API
-// where output can be unbuffered.
-template <typename Context> class basic_format_arg {
- private:
-  detail::value<Context> value_;
-  detail::type type_;
+  FMT_CONSTEXPR20 ~buffer() = default;
+  buffer(buffer&&) = default;
 
-  template <typename ContextType, typename T>
-  friend FMT_CONSTEXPR auto detail::make_arg(T& value)
-      -> basic_format_arg<ContextType>;
+  /// Sets the buffer data and capacity.
+  FMT_CONSTEXPR void set(T* buf_data, size_t buf_capacity) noexcept {
+    ptr_ = buf_data;
+    capacity_ = buf_capacity;
+  }
 
-  friend class basic_format_args<Context>;
-  friend class dynamic_format_arg_store<Context>;
+ public:
+  using value_type = T;
+  using const_reference = const T&;
 
-  using char_type = typename Context::char_type;
+  buffer(const buffer&) = delete;
+  void operator=(const buffer&) = delete;
 
-  template <typename, size_t, size_t, unsigned long long>
-  friend struct detail::format_arg_store;
+  auto begin() noexcept -> T* { return ptr_; }
+  auto end() noexcept -> T* { return ptr_ + size_; }
 
-  basic_format_arg(const detail::named_arg_info<char_type>* args, size_t size)
-      : value_(args, size) {}
+  auto begin() const noexcept -> const T* { return ptr_; }
+  auto end() const noexcept -> const T* { return ptr_ + size_; }
 
- public:
-  class handle {
-   public:
-    explicit handle(detail::custom_value<Context> custom) : custom_(custom) {}
+  /// Returns the size of this buffer.
+  constexpr auto size() const noexcept -> size_t { return size_; }
 
-    void format(typename Context::parse_context_type& parse_ctx,
-                Context& ctx) const {
-      custom_.format(custom_.value, parse_ctx, ctx);
-    }
+  /// Returns the capacity of this buffer.
+  constexpr auto capacity() const noexcept -> size_t { return capacity_; }
 
-   private:
-    detail::custom_value<Context> custom_;
-  };
+  /// Returns a pointer to the buffer data (not null-terminated).
+  FMT_CONSTEXPR auto data() noexcept -> T* { return ptr_; }
+  FMT_CONSTEXPR auto data() const noexcept -> const T* { return ptr_; }
 
-  constexpr basic_format_arg() : type_(detail::type::none_type) {}
+  /// Clears this buffer.
+  FMT_CONSTEXPR void clear() { size_ = 0; }
 
-  constexpr explicit operator bool() const noexcept {
-    return type_ != detail::type::none_type;
+  // Tries resizing the buffer to contain `count` elements. If T is a POD type
+  // the new elements may not be initialized.
+  FMT_CONSTEXPR void try_resize(size_t count) {
+    try_reserve(count);
+    size_ = min_of(count, capacity_);
   }
 
-  auto type() const -> detail::type { return type_; }
+  // Tries increasing the buffer capacity to `new_capacity`. It can increase the
+  // capacity by a smaller amount than requested but guarantees there is space
+  // for at least one additional element either by increasing the capacity or by
+  // flushing the buffer if it is full.
+  FMT_CONSTEXPR void try_reserve(size_t new_capacity) {
+    if (new_capacity > capacity_) grow_(*this, new_capacity);
+  }
 
-  auto is_integral() const -> bool { return detail::is_integral_type(type_); }
-  auto is_arithmetic() const -> bool {
-    return detail::is_arithmetic_type(type_);
+  FMT_CONSTEXPR void push_back(const T& value) {
+    try_reserve(size_ + 1);
+    ptr_[size_++] = value;
   }
 
-  /**
-   * Visits an argument dispatching to the appropriate visit method based on
-   * the argument type. For example, if the argument type is `double` then
-   * `vis(value)` will be called with the value of type `double`.
-   */
-  template <typename Visitor>
-  FMT_CONSTEXPR auto visit(Visitor&& vis) -> decltype(vis(0)) {
-    switch (type_) {
-    case detail::type::none_type:
-      break;
-    case detail::type::int_type:
-      return vis(value_.int_value);
-    case detail::type::uint_type:
-      return vis(value_.uint_value);
-    case detail::type::long_long_type:
-      return vis(value_.long_long_value);
-    case detail::type::ulong_long_type:
-      return vis(value_.ulong_long_value);
-    case detail::type::int128_type:
-      return vis(detail::convert_for_visit(value_.int128_value));
-    case detail::type::uint128_type:
-      return vis(detail::convert_for_visit(value_.uint128_value));
-    case detail::type::bool_type:
-      return vis(value_.bool_value);
-    case detail::type::char_type:
-      return vis(value_.char_value);
-    case detail::type::float_type:
-      return vis(value_.float_value);
-    case detail::type::double_type:
-      return vis(value_.double_value);
-    case detail::type::long_double_type:
-      return vis(value_.long_double_value);
-    case detail::type::cstring_type:
-      return vis(value_.string.data);
-    case detail::type::string_type:
-      using sv = basic_string_view<typename Context::char_type>;
-      return vis(sv(value_.string.data, value_.string.size));
-    case detail::type::pointer_type:
-      return vis(value_.pointer);
-    case detail::type::custom_type:
-      return vis(typename basic_format_arg<Context>::handle(value_.custom));
+  /// Appends data to the end of the buffer.
+  template <typename U>
+// Workaround for MSVC2019 to fix error C2893: Failed to specialize function
+// template 'void fmt::v11::detail::buffer<T>::append(const U *,const U *)'.
+#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1940
+  FMT_CONSTEXPR20
+#endif
+      void
+      append(const U* begin, const U* end) {
+    while (begin != end) {
+      auto size = size_;
+      auto free_cap = capacity_ - size;
+      auto count = to_unsigned(end - begin);
+      if (free_cap < count) {
+        grow_(*this, size + count);
+        size = size_;
+        free_cap = capacity_ - size;
+        count = count < free_cap ? count : free_cap;
+      }
+      // A loop is faster than memcpy on small sizes.
+      T* out = ptr_ + size;
+      for (size_t i = 0; i < count; ++i) out[i] = begin[i];
+      size_ += count;
+      begin += count;
     }
-    return vis(monostate());
   }
 
-  auto format_custom(const char_type* parse_begin,
-                     typename Context::parse_context_type& parse_ctx,
-                     Context& ctx) -> bool {
-    if (type_ != detail::type::custom_type) return false;
-    parse_ctx.advance_to(parse_begin);
-    value_.custom.format(value_.custom.value, parse_ctx, ctx);
-    return true;
+  template <typename Idx> FMT_CONSTEXPR auto operator[](Idx index) -> T& {
+    return ptr_[index];
+  }
+  template <typename Idx>
+  FMT_CONSTEXPR auto operator[](Idx index) const -> const T& {
+    return ptr_[index];
   }
 };
 
-template <typename Visitor, typename Context>
-FMT_DEPRECATED FMT_CONSTEXPR auto visit_format_arg(
-    Visitor&& vis, const basic_format_arg<Context>& arg) -> decltype(vis(0)) {
-  return arg.visit(static_cast<Visitor&&>(vis));
-}
+struct buffer_traits {
+  constexpr explicit buffer_traits(size_t) {}
+  constexpr auto count() const -> size_t { return 0; }
+  constexpr auto limit(size_t size) const -> size_t { return size; }
+};
+
+class fixed_buffer_traits {
+ private:
+  size_t count_ = 0;
+  size_t limit_;
 
-/**
- * A view of a collection of formatting arguments. To avoid lifetime issues it
- * should only be used as a parameter type in type-erased functions such as
- * `vformat`:
- *
- *     void vlog(fmt::string_view fmt, fmt::format_args args);  // OK
- *     fmt::format_args args = fmt::make_format_args();  // Dangling reference
- */
-template <typename Context> class basic_format_args {
  public:
-  using size_type = int;
-  using format_arg = basic_format_arg<Context>;
+  constexpr explicit fixed_buffer_traits(size_t limit) : limit_(limit) {}
+  constexpr auto count() const -> size_t { return count_; }
+  FMT_CONSTEXPR auto limit(size_t size) -> size_t {
+    size_t n = limit_ > count_ ? limit_ - count_ : 0;
+    count_ += size;
+    return min_of(size, n);
+  }
+};
 
+// A buffer that writes to an output iterator when flushed.
+template <typename OutputIt, typename T, typename Traits = buffer_traits>
+class iterator_buffer : public Traits, public buffer<T> {
  private:
-  // A descriptor that contains information about formatting arguments.
-  // If the number of arguments is less or equal to max_packed_args then
-  // argument types are passed in the descriptor. This reduces binary code size
-  // per formatting function call.
-  unsigned long long desc_;
-  union {
-    // If is_packed() returns true then argument values are stored in values_;
-    // otherwise they are stored in args_. This is done to improve cache
-    // locality and reduce compiled code size since storing larger objects
-    // may require more code (at least on x86-64) even if the same amount of
-    // data is actually copied to stack. It saves ~10% on the bloat test.
-    const detail::value<Context>* values_;
-    const format_arg* args_;
-  };
+  OutputIt out_;
+  enum { buffer_size = 256 };
+  T data_[buffer_size];
 
-  constexpr auto is_packed() const -> bool {
-    return (desc_ & detail::is_unpacked_bit) == 0;
-  }
-  constexpr auto has_named_args() const -> bool {
-    return (desc_ & detail::has_named_args_bit) != 0;
+  static FMT_CONSTEXPR void grow(buffer<T>& buf, size_t) {
+    if (buf.size() == buffer_size) static_cast<iterator_buffer&>(buf).flush();
   }
 
-  FMT_CONSTEXPR auto type(int index) const -> detail::type {
-    int shift = index * detail::packed_arg_bits;
-    unsigned int mask = (1 << detail::packed_arg_bits) - 1;
-    return static_cast<detail::type>((desc_ >> shift) & mask);
+  void flush() {
+    auto size = this->size();
+    this->clear();
+    const T* begin = data_;
+    const T* end = begin + this->limit(size);
+    while (begin != end) *out_++ = *begin++;
   }
 
  public:
-  constexpr basic_format_args() : desc_(0), args_(nullptr) {}
-
-  /// Constructs a `basic_format_args` object from `format_arg_store`.
-  template <size_t NUM_ARGS, size_t NUM_NAMED_ARGS, unsigned long long DESC,
-            FMT_ENABLE_IF(NUM_ARGS <= detail::max_packed_args)>
-  constexpr FMT_ALWAYS_INLINE basic_format_args(
-      const detail::format_arg_store<Context, NUM_ARGS, NUM_NAMED_ARGS, DESC>&
-          store)
-      : desc_(DESC), values_(store.args + (NUM_NAMED_ARGS != 0 ? 1 : 0)) {}
-
-  template <size_t NUM_ARGS, size_t NUM_NAMED_ARGS, unsigned long long DESC,
-            FMT_ENABLE_IF(NUM_ARGS > detail::max_packed_args)>
-  constexpr basic_format_args(
-      const detail::format_arg_store<Context, NUM_ARGS, NUM_NAMED_ARGS, DESC>&
-          store)
-      : desc_(DESC), args_(store.args + (NUM_NAMED_ARGS != 0 ? 1 : 0)) {}
+  explicit iterator_buffer(OutputIt out, size_t n = buffer_size)
+      : Traits(n), buffer<T>(grow, data_, 0, buffer_size), out_(out) {}
+  iterator_buffer(iterator_buffer&& other) noexcept
+      : Traits(other),
+        buffer<T>(grow, data_, 0, buffer_size),
+        out_(other.out_) {}
+  ~iterator_buffer() {
+    // Don't crash if flush fails during unwinding.
+    FMT_TRY { flush(); }
+    FMT_CATCH(...) {}
+  }
 
-  /// Constructs a `basic_format_args` object from `dynamic_format_arg_store`.
-  constexpr basic_format_args(const dynamic_format_arg_store<Context>& store)
-      : desc_(store.get_types()), args_(store.data()) {}
+  auto out() -> OutputIt {
+    flush();
+    return out_;
+  }
+  auto count() const -> size_t { return Traits::count() + this->size(); }
+};
 
-  /// Constructs a `basic_format_args` object from a dynamic list of arguments.
-  constexpr basic_format_args(const format_arg* args, int count)
-      : desc_(detail::is_unpacked_bit | detail::to_unsigned(count)),
-        args_(args) {}
+template <typename T>
+class iterator_buffer<T*, T, fixed_buffer_traits> : public fixed_buffer_traits,
+                                                    public buffer<T> {
+ private:
+  T* out_;
+  enum { buffer_size = 256 };
+  T data_[buffer_size];
 
-  /// Returns the argument with the specified id.
-  FMT_CONSTEXPR auto get(int id) const -> format_arg {
-    format_arg arg;
-    if (!is_packed()) {
-      if (id < max_size()) arg = args_[id];
-      return arg;
-    }
-    if (static_cast<unsigned>(id) >= detail::max_packed_args) return arg;
-    arg.type_ = type(id);
-    if (arg.type_ == detail::type::none_type) return arg;
-    arg.value_ = values_[id];
-    return arg;
+  static FMT_CONSTEXPR void grow(buffer<T>& buf, size_t) {
+    if (buf.size() == buf.capacity())
+      static_cast<iterator_buffer&>(buf).flush();
   }
 
-  template <typename Char>
-  auto get(basic_string_view<Char> name) const -> format_arg {
-    int id = get_id(name);
-    return id >= 0 ? get(id) : format_arg();
+  void flush() {
+    size_t n = this->limit(this->size());
+    if (this->data() == out_) {
+      out_ += n;
+      this->set(data_, buffer_size);
+    }
+    this->clear();
   }
 
-  template <typename Char>
-  FMT_CONSTEXPR auto get_id(basic_string_view<Char> name) const -> int {
-    if (!has_named_args()) return -1;
-    const auto& named_args =
-        (is_packed() ? values_[-1] : args_[-1].value_).named_args;
-    for (size_t i = 0; i < named_args.size; ++i) {
-      if (named_args.data[i].name == name) return named_args.data[i].id;
+ public:
+  explicit iterator_buffer(T* out, size_t n = buffer_size)
+      : fixed_buffer_traits(n), buffer<T>(grow, out, 0, n), out_(out) {}
+  iterator_buffer(iterator_buffer&& other) noexcept
+      : fixed_buffer_traits(other),
+        buffer<T>(static_cast<iterator_buffer&&>(other)),
+        out_(other.out_) {
+    if (this->data() != out_) {
+      this->set(data_, buffer_size);
+      this->clear();
     }
-    return -1;
   }
+  ~iterator_buffer() { flush(); }
 
-  auto max_size() const -> int {
-    unsigned long long max_packed = detail::max_packed_args;
-    return static_cast<int>(is_packed() ? max_packed
-                                        : desc_ & ~detail::is_unpacked_bit);
+  auto out() -> T* {
+    flush();
+    return out_;
+  }
+  auto count() const -> size_t {
+    return fixed_buffer_traits::count() + this->size();
   }
 };
 
-// A formatting context.
-class context {
- private:
-  appender out_;
-  basic_format_args<context> args_;
-  detail::locale_ref loc_;
-
+template <typename T> class iterator_buffer<T*, T> : public buffer<T> {
  public:
-  /// The character type for the output.
-  using char_type = char;
+  explicit iterator_buffer(T* out, size_t = 0)
+      : buffer<T>([](buffer<T>&, size_t) {}, out, 0, ~size_t()) {}
 
-  using iterator = appender;
-  using format_arg = basic_format_arg<context>;
-  using parse_context_type = basic_format_parse_context<char>;
-  template <typename T> using formatter_type = formatter<T, char>;
-
-  /// Constructs a `basic_format_context` object. References to the arguments
-  /// are stored in the object so make sure they have appropriate lifetimes.
-  FMT_CONSTEXPR context(iterator out, basic_format_args<context> ctx_args,
-                        detail::locale_ref loc = {})
-      : out_(out), args_(ctx_args), loc_(loc) {}
-  context(context&&) = default;
-  context(const context&) = delete;
-  void operator=(const context&) = delete;
+  auto out() -> T* { return &*this->end(); }
+};
+
+template <typename Container>
+class container_buffer : public buffer<typename Container::value_type> {
+ private:
+  using value_type = typename Container::value_type;
 
-  FMT_CONSTEXPR auto arg(int id) const -> format_arg { return args_.get(id); }
-  auto arg(string_view name) -> format_arg { return args_.get(name); }
-  FMT_CONSTEXPR auto arg_id(string_view name) -> int {
-    return args_.get_id(name);
+  static FMT_CONSTEXPR void grow(buffer<value_type>& buf, size_t capacity) {
+    auto& self = static_cast<container_buffer&>(buf);
+    self.container.resize(capacity);
+    self.set(&self.container[0], capacity);
   }
-  auto args() const -> const basic_format_args<context>& { return args_; }
 
-  // Returns an iterator to the beginning of the output range.
-  FMT_CONSTEXPR auto out() -> iterator { return out_; }
+ public:
+  Container& container;
 
-  // Advances the begin iterator to `it`.
-  void advance_to(iterator) {}
+  explicit container_buffer(Container& c)
+      : buffer<value_type>(grow, c.size()), container(c) {}
+};
+
+// A buffer that writes to a container with the contiguous storage.
+template <typename OutputIt>
+class iterator_buffer<
+    OutputIt,
+    enable_if_t<is_back_insert_iterator<OutputIt>::value &&
+                    is_contiguous<typename OutputIt::container_type>::value,
+                typename OutputIt::container_type::value_type>>
+    : public container_buffer<typename OutputIt::container_type> {
+ private:
+  using base = container_buffer<typename OutputIt::container_type>;
 
-  FMT_CONSTEXPR auto locale() -> detail::locale_ref { return loc_; }
+ public:
+  explicit iterator_buffer(typename OutputIt::container_type& c) : base(c) {}
+  explicit iterator_buffer(OutputIt out, size_t = 0)
+      : base(get_container(out)) {}
+
+  auto out() -> OutputIt { return OutputIt(this->container); }
 };
 
-template <typename OutputIt, typename Char> class generic_context;
+// A buffer that counts the number of code units written discarding the output.
+template <typename T = char> class counting_buffer : public buffer<T> {
+ private:
+  enum { buffer_size = 256 };
+  T data_[buffer_size];
+  size_t count_ = 0;
 
-// Longer aliases for C++20 compatibility.
-template <typename OutputIt, typename Char>
-using basic_format_context =
-    conditional_t<std::is_same<OutputIt, appender>::value, context,
-                  generic_context<OutputIt, Char>>;
-using format_context = context;
+  static FMT_CONSTEXPR void grow(buffer<T>& buf, size_t) {
+    if (buf.size() != buffer_size) return;
+    static_cast<counting_buffer&>(buf).count_ += buf.size();
+    buf.clear();
+  }
 
-template <typename Char>
-using buffered_context = basic_format_context<basic_appender<Char>, Char>;
+ public:
+  FMT_CONSTEXPR counting_buffer() : buffer<T>(grow, data_, 0, buffer_size) {}
 
-template <typename T, typename Char = char>
-using is_formattable = bool_constant<!std::is_base_of<
-    detail::unformattable, decltype(detail::arg_mapper<buffered_context<Char>>()
-                                        .map(std::declval<T&>()))>::value>;
+  constexpr auto count() const noexcept -> size_t {
+    return count_ + this->size();
+  }
+};
 
-#if FMT_USE_CONCEPTS
-template <typename T, typename Char = char>
-concept formattable = is_formattable<remove_reference_t<T>, Char>::value;
-#endif
+template <typename T>
+struct is_back_insert_iterator<basic_appender<T>> : std::true_type {};
+
+template <typename OutputIt, typename InputIt, typename = void>
+struct has_back_insert_iterator_container_append : std::false_type {};
+template <typename OutputIt, typename InputIt>
+struct has_back_insert_iterator_container_append<
+    OutputIt, InputIt,
+    void_t<decltype(get_container(std::declval<OutputIt>())
+                        .append(std::declval<InputIt>(),
+                                std::declval<InputIt>()))>> : std::true_type {};
+
+template <typename OutputIt, typename InputIt, typename = void>
+struct has_back_insert_iterator_container_insert_at_end : std::false_type {};
+
+template <typename OutputIt, typename InputIt>
+struct has_back_insert_iterator_container_insert_at_end<
+    OutputIt, InputIt,
+    void_t<decltype(get_container(std::declval<OutputIt>())
+                        .insert(get_container(std::declval<OutputIt>()).end(),
+                                std::declval<InputIt>(),
+                                std::declval<InputIt>()))>> : std::true_type {};
 
-/**
- * Constructs an object that stores references to arguments and can be
- * implicitly converted to `format_args`. `Context` can be omitted in which case
- * it defaults to `format_context`. See `arg` for lifetime considerations.
- */
-// Take arguments by lvalue references to avoid some lifetime issues, e.g.
-//   auto args = make_format_args(std::string());
-template <typename Context = format_context, typename... T,
-          size_t NUM_ARGS = sizeof...(T),
-          size_t NUM_NAMED_ARGS = detail::count_named_args<T...>(),
-          unsigned long long DESC = detail::make_descriptor<Context, T...>(),
-          FMT_ENABLE_IF(NUM_NAMED_ARGS == 0)>
-constexpr FMT_ALWAYS_INLINE auto make_format_args(T&... args)
-    -> detail::format_arg_store<Context, NUM_ARGS, 0, DESC> {
-  return {{detail::make_arg<NUM_ARGS <= detail::max_packed_args, Context>(
-      args)...}};
-}
-
-#ifndef FMT_DOC
-template <typename Context = format_context, typename... T,
-          size_t NUM_NAMED_ARGS = detail::count_named_args<T...>(),
-          unsigned long long DESC =
-              detail::make_descriptor<Context, T...>() |
-              static_cast<unsigned long long>(detail::has_named_args_bit),
-          FMT_ENABLE_IF(NUM_NAMED_ARGS != 0)>
-constexpr auto make_format_args(T&... args)
-    -> detail::format_arg_store<Context, sizeof...(T), NUM_NAMED_ARGS, DESC> {
-  return {args...};
+// An optimized version of std::copy with the output value type (T).
+template <typename T, typename InputIt, typename OutputIt,
+          FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value&&
+                            has_back_insert_iterator_container_append<
+                                OutputIt, InputIt>::value)>
+FMT_CONSTEXPR20 auto copy(InputIt begin, InputIt end, OutputIt out)
+    -> OutputIt {
+  get_container(out).append(begin, end);
+  return out;
 }
-#endif
 
-/**
- * Returns a named argument to be used in a formatting function.
- * It should only be used in a call to a formatting function or
- * `dynamic_format_arg_store::push_back`.
- *
- * **Example**:
- *
- *     fmt::print("The answer is {answer}.", fmt::arg("answer", 42));
- */
-template <typename Char, typename T>
-inline auto arg(const Char* name, const T& arg) -> detail::named_arg<Char, T> {
-  static_assert(!detail::is_named_arg<T>(), "nested named arguments");
-  return {name, arg};
+template <typename T, typename InputIt, typename OutputIt,
+          FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value &&
+                        !has_back_insert_iterator_container_append<
+                            OutputIt, InputIt>::value &&
+                        has_back_insert_iterator_container_insert_at_end<
+                            OutputIt, InputIt>::value)>
+FMT_CONSTEXPR20 auto copy(InputIt begin, InputIt end, OutputIt out)
+    -> OutputIt {
+  auto& c = get_container(out);
+  c.insert(c.end(), begin, end);
+  return out;
 }
-FMT_END_EXPORT
 
-/// An alias for `basic_format_args<format_context>`.
-// A separate type would result in shorter symbols but break ABI compatibility
-// between clang and gcc on ARM (#1919).
-FMT_EXPORT using format_args = basic_format_args<format_context>;
-
-// We cannot use enum classes as bit fields because of a gcc bug, so we put them
-// in namespaces instead (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61414).
-// Additionally, if an underlying type is specified, older gcc incorrectly warns
-// that the type is too small. Both bugs are fixed in gcc 9.3.
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 903
-#  define FMT_ENUM_UNDERLYING_TYPE(type)
-#else
-#  define FMT_ENUM_UNDERLYING_TYPE(type) : type
-#endif
-namespace align {
-enum type FMT_ENUM_UNDERLYING_TYPE(unsigned char){none, left, right, center,
-                                                  numeric};
-}
-using align_t = align::type;
-namespace sign {
-enum type FMT_ENUM_UNDERLYING_TYPE(unsigned char){none, minus, plus, space};
+template <typename T, typename InputIt, typename OutputIt,
+          FMT_ENABLE_IF(!(is_back_insert_iterator<OutputIt>::value &&
+                          (has_back_insert_iterator_container_append<
+                               OutputIt, InputIt>::value ||
+                           has_back_insert_iterator_container_insert_at_end<
+                               OutputIt, InputIt>::value)))>
+FMT_CONSTEXPR auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
+  while (begin != end) *out++ = static_cast<T>(*begin++);
+  return out;
 }
-using sign_t = sign::type;
 
-namespace detail {
-
-template <typename Char>
-using unsigned_char = typename conditional_t<std::is_integral<Char>::value,
-                                             std::make_unsigned<Char>,
-                                             type_identity<unsigned>>::type;
-
-// Character (code unit) type is erased to prevent template bloat.
-struct fill_t {
- private:
-  enum { max_size = 4 };
-  char data_[max_size] = {' '};
-  unsigned char size_ = 1;
+template <typename T, typename V, typename OutputIt>
+FMT_CONSTEXPR auto copy(basic_string_view<V> s, OutputIt out) -> OutputIt {
+  return copy<T>(s.begin(), s.end(), out);
+}
 
- public:
-  template <typename Char>
-  FMT_CONSTEXPR void operator=(basic_string_view<Char> s) {
-    auto size = s.size();
-    size_ = static_cast<unsigned char>(size);
-    if (size == 1) {
-      unsigned uchar = static_cast<unsigned_char<Char>>(s[0]);
-      data_[0] = static_cast<char>(uchar);
-      data_[1] = static_cast<char>(uchar >> 8);
-      return;
-    }
-    FMT_ASSERT(size <= max_size, "invalid fill");
-    for (size_t i = 0; i < size; ++i) data_[i] = static_cast<char>(s[i]);
-  }
+template <typename It, typename Enable = std::true_type>
+struct is_buffer_appender : std::false_type {};
+template <typename It>
+struct is_buffer_appender<
+    It, bool_constant<
+            is_back_insert_iterator<It>::value &&
+            std::is_base_of<buffer<typename It::container_type::value_type>,
+                            typename It::container_type>::value>>
+    : std::true_type {};
 
-  FMT_CONSTEXPR void operator=(char c) {
-    data_[0] = c;
-    size_ = 1;
-  }
+// Maps an output iterator to a buffer.
+template <typename T, typename OutputIt,
+          FMT_ENABLE_IF(!is_buffer_appender<OutputIt>::value)>
+auto get_buffer(OutputIt out) -> iterator_buffer<OutputIt, T> {
+  return iterator_buffer<OutputIt, T>(out);
+}
+template <typename T, typename OutputIt,
+          FMT_ENABLE_IF(is_buffer_appender<OutputIt>::value)>
+auto get_buffer(OutputIt out) -> buffer<T>& {
+  return get_container(out);
+}
 
-  constexpr auto size() const -> size_t { return size_; }
+template <typename Buf, typename OutputIt>
+auto get_iterator(Buf& buf, OutputIt) -> decltype(buf.out()) {
+  return buf.out();
+}
+template <typename T, typename OutputIt>
+auto get_iterator(buffer<T>&, OutputIt out) -> OutputIt {
+  return out;
+}
 
-  template <typename Char> constexpr auto get() const -> Char {
-    using uchar = unsigned char;
-    return static_cast<Char>(static_cast<uchar>(data_[0]) |
-                             (static_cast<uchar>(data_[1]) << 8));
-  }
+// This type is intentionally undefined, only used for errors.
+template <typename T, typename Char> struct type_is_unformattable_for;
 
-  template <typename Char, FMT_ENABLE_IF(std::is_same<Char, char>::value)>
-  constexpr auto data() const -> const Char* {
-    return data_;
-  }
-  template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
-  constexpr auto data() const -> const Char* {
-    return nullptr;
-  }
+template <typename Char> struct string_value {
+  const Char* data;
+  size_t size;
+  auto str() const -> basic_string_view<Char> { return {data, size}; }
 };
-}  // namespace detail
-
-enum class presentation_type : unsigned char {
-  // Common specifiers:
-  none = 0,
-  debug = 1,   // '?'
-  string = 2,  // 's' (string, bool)
-
-  // Integral, bool and character specifiers:
-  dec = 3,  // 'd'
-  hex,      // 'x' or 'X'
-  oct,      // 'o'
-  bin,      // 'b' or 'B'
-  chr,      // 'c'
-
-  // String and pointer specifiers:
-  pointer = 3,  // 'p'
 
-  // Floating-point specifiers:
-  exp = 1,  // 'e' or 'E' (1 since there is no FP debug presentation)
-  fixed,    // 'f' or 'F'
-  general,  // 'g' or 'G'
-  hexfloat  // 'a' or 'A'
+template <typename Context> struct custom_value {
+  using char_type = typename Context::char_type;
+  void* value;
+  void (*format)(void* arg, parse_context<char_type>& parse_ctx, Context& ctx);
 };
 
-// Format specifiers for built-in and string types.
-struct format_specs {
-  int width;
-  int precision;
-  presentation_type type;
-  align_t align : 4;
-  sign_t sign : 3;
-  bool upper : 1;  // An uppercase version e.g. 'X' for 'x'.
-  bool alt : 1;    // Alternate form ('#').
-  bool localized : 1;
-  detail::fill_t fill;
-
-  constexpr format_specs()
-      : width(0),
-        precision(-1),
-        type(presentation_type::none),
-        align(align::none),
-        sign(sign::none),
-        upper(false),
-        alt(false),
-        localized(false) {}
+template <typename Char> struct named_arg_value {
+  const named_arg_info<Char>* data;
+  size_t size;
 };
 
-namespace detail {
-
-enum class arg_id_kind { none, index, name };
+struct custom_tag {};
 
-// An argument reference.
-template <typename Char> struct arg_ref {
-  FMT_CONSTEXPR arg_ref() : kind(arg_id_kind::none), val() {}
+#if !FMT_BUILTIN_TYPES
+#  define FMT_BUILTIN , monostate
+#else
+#  define FMT_BUILTIN
+#endif
 
-  FMT_CONSTEXPR explicit arg_ref(int index)
-      : kind(arg_id_kind::index), val(index) {}
-  FMT_CONSTEXPR explicit arg_ref(basic_string_view<Char> name)
-      : kind(arg_id_kind::name), val(name) {}
+// A formatting argument value.
+template <typename Context> class value {
+ public:
+  using char_type = typename Context::char_type;
 
-  FMT_CONSTEXPR auto operator=(int idx) -> arg_ref& {
-    kind = arg_id_kind::index;
-    val.index = idx;
-    return *this;
-  }
+  union {
+    monostate no_value;
+    int int_value;
+    unsigned uint_value;
+    long long long_long_value;
+    unsigned long long ulong_long_value;
+    int128_opt int128_value;
+    uint128_opt uint128_value;
+    bool bool_value;
+    char_type char_value;
+    float float_value;
+    double double_value;
+    long double long_double_value;
+    const void* pointer;
+    string_value<char_type> string;
+    custom_value<Context> custom;
+    named_arg_value<char_type> named_args;
+  };
 
-  arg_id_kind kind;
-  union value {
-    FMT_CONSTEXPR value(int idx = 0) : index(idx) {}
-    FMT_CONSTEXPR value(basic_string_view<Char> n) : name(n) {}
+  constexpr FMT_INLINE value() : no_value() {}
+  constexpr FMT_INLINE value(signed char x) : int_value(x) {}
+  constexpr FMT_INLINE value(unsigned char x FMT_BUILTIN) : uint_value(x) {}
+  constexpr FMT_INLINE value(signed short x) : int_value(x) {}
+  constexpr FMT_INLINE value(unsigned short x FMT_BUILTIN) : uint_value(x) {}
+  constexpr FMT_INLINE value(int x) : int_value(x) {}
+  constexpr FMT_INLINE value(unsigned x FMT_BUILTIN) : uint_value(x) {}
+  FMT_CONSTEXPR FMT_INLINE value(long x FMT_BUILTIN) : value(long_type(x)) {}
+  FMT_CONSTEXPR FMT_INLINE value(unsigned long x FMT_BUILTIN)
+      : value(ulong_type(x)) {}
+  constexpr FMT_INLINE value(long long x FMT_BUILTIN) : long_long_value(x) {}
+  constexpr FMT_INLINE value(unsigned long long x FMT_BUILTIN)
+      : ulong_long_value(x) {}
+  FMT_INLINE value(int128_opt x FMT_BUILTIN) : int128_value(x) {}
+  FMT_INLINE value(uint128_opt x FMT_BUILTIN) : uint128_value(x) {}
+  constexpr FMT_INLINE value(bool x FMT_BUILTIN) : bool_value(x) {}
+
+  template <int N>
+  constexpr FMT_INLINE value(bitint<N> x FMT_BUILTIN) : long_long_value(x) {
+    static_assert(N <= 64, "unsupported _BitInt");
+  }
+  template <int N>
+  constexpr FMT_INLINE value(ubitint<N> x FMT_BUILTIN) : ulong_long_value(x) {
+    static_assert(N <= 64, "unsupported _BitInt");
+  }
+
+  template <typename T, FMT_ENABLE_IF(is_code_unit<T>::value)>
+  constexpr FMT_INLINE value(T x FMT_BUILTIN) : char_value(x) {
+    static_assert(
+        std::is_same<T, char>::value || std::is_same<T, char_type>::value,
+        "mixing character types is disallowed");
+  }
+
+  constexpr FMT_INLINE value(float x FMT_BUILTIN) : float_value(x) {}
+  constexpr FMT_INLINE value(double x FMT_BUILTIN) : double_value(x) {}
+  FMT_INLINE value(long double x FMT_BUILTIN) : long_double_value(x) {}
+
+  FMT_CONSTEXPR FMT_INLINE value(char_type* x FMT_BUILTIN) {
+    string.data = x;
+    if (is_constant_evaluated()) string.size = 0;
+  }
+  FMT_CONSTEXPR FMT_INLINE value(const char_type* x FMT_BUILTIN) {
+    string.data = x;
+    if (is_constant_evaluated()) string.size = 0;
+  }
+  template <typename T, typename C = char_t<T>,
+            FMT_ENABLE_IF(!std::is_pointer<T>::value)>
+  FMT_CONSTEXPR value(const T& x FMT_BUILTIN) {
+    static_assert(std::is_same<C, char_type>::value,
+                  "mixing character types is disallowed");
+    auto sv = to_string_view(x);
+    string.data = sv.data();
+    string.size = sv.size();
+  }
+  FMT_INLINE value(void* x FMT_BUILTIN) : pointer(x) {}
+  FMT_INLINE value(const void* x FMT_BUILTIN) : pointer(x) {}
+  FMT_INLINE value(volatile void* x FMT_BUILTIN)
+      : pointer(const_cast<const void*>(x)) {}
+  FMT_INLINE value(const volatile void* x FMT_BUILTIN)
+      : pointer(const_cast<const void*>(x)) {}
+  FMT_INLINE value(nullptr_t) : pointer(nullptr) {}
+
+  template <typename T, FMT_ENABLE_IF(std::is_pointer<T>::value ||
+                                      std::is_member_pointer<T>::value)>
+  value(const T&) {
+    // Formatting of arbitrary pointers is disallowed. If you want to format a
+    // pointer cast it to `void*` or `const void*`. In particular, this forbids
+    // formatting of `[const] volatile char*` printed as bool by iostreams.
+    static_assert(sizeof(T) == 0,
+                  "formatting of non-void pointers is disallowed");
+  }
+
+  template <typename T, FMT_ENABLE_IF(use_format_as<T>::value)>
+  value(const T& x) : value(format_as(x)) {}
+  template <typename T, FMT_ENABLE_IF(use_format_as_member<T>::value)>
+  value(const T& x) : value(formatter<T>::format_as(x)) {}
 
-    int index;
-    basic_string_view<Char> name;
-  } val;
-};
+  template <typename T, FMT_ENABLE_IF(is_named_arg<T>::value)>
+  value(const T& named_arg) : value(named_arg.value) {}
 
-// Format specifiers with width and precision resolved at formatting rather
-// than parsing time to allow reusing the same parsed specifiers with
-// different sets of arguments (precompilation of format strings).
-template <typename Char = char> struct dynamic_format_specs : format_specs {
-  arg_ref<Char> width_ref;
-  arg_ref<Char> precision_ref;
-};
+  template <typename T,
+            FMT_ENABLE_IF(use_formatter<T>::value || !FMT_BUILTIN_TYPES)>
+  FMT_CONSTEXPR20 FMT_INLINE value(T& x) : value(x, custom_tag()) {}
 
-// Converts a character to ASCII. Returns '\0' on conversion failure.
-template <typename Char, FMT_ENABLE_IF(std::is_integral<Char>::value)>
-constexpr auto to_ascii(Char c) -> char {
-  return c <= 0xff ? static_cast<char>(c) : '\0';
-}
+  FMT_ALWAYS_INLINE value(const named_arg_info<char_type>* args, size_t size)
+      : named_args{args, size} {}
 
-// Returns the number of code units in a code point or 1 on error.
-template <typename Char>
-FMT_CONSTEXPR auto code_point_length(const Char* begin) -> int {
-  if (const_check(sizeof(Char) != 1)) return 1;
-  auto c = static_cast<unsigned char>(*begin);
-  return static_cast<int>((0x3a55000000000000ull >> (2 * (c >> 3))) & 0x3) + 1;
-}
+ private:
+  template <typename T, FMT_ENABLE_IF(has_formatter<T, char_type>())>
+  FMT_CONSTEXPR value(T& x, custom_tag) {
+    using value_type = remove_const_t<T>;
+    // T may overload operator& e.g. std::vector<bool>::reference in libc++.
+    if (!is_constant_evaluated()) {
+      custom.value =
+          const_cast<char*>(&reinterpret_cast<const volatile char&>(x));
+    } else {
+      custom.value = nullptr;
+#if defined(__cpp_if_constexpr)
+      if constexpr (std::is_same<decltype(&x), remove_reference_t<T>*>::value)
+        custom.value = const_cast<value_type*>(&x);
+#endif
+    }
+    custom.format = format_custom<value_type>;
+  }
 
-// Return the result via the out param to workaround gcc bug 77539.
-template <bool IS_CONSTEXPR, typename T, typename Ptr = const T*>
-FMT_CONSTEXPR auto find(Ptr first, Ptr last, T value, Ptr& out) -> bool {
-  for (out = first; out != last; ++out) {
-    if (*out == value) return true;
+  template <typename T, FMT_ENABLE_IF(!has_formatter<T, char_type>())>
+  FMT_CONSTEXPR value(const T&, custom_tag) {
+    // Cannot format an argument; to make type T formattable provide a
+    // formatter<T> specialization: https://fmt.dev/latest/api.html#udt.
+    type_is_unformattable_for<T, char_type> _;
   }
-  return false;
-}
 
-template <>
-inline auto find<false, char>(const char* first, const char* last, char value,
-                              const char*& out) -> bool {
-  out =
-      static_cast<const char*>(memchr(first, value, to_unsigned(last - first)));
-  return out != nullptr;
-}
+  // Formats an argument of a custom type, such as a user-defined class.
+  template <typename T>
+  static void format_custom(void* arg, parse_context<char_type>& parse_ctx,
+                            Context& ctx) {
+    auto f = formatter<T, char_type>();
+    parse_ctx.advance_to(f.parse(parse_ctx));
+    using qualified_type =
+        conditional_t<has_formatter<const T, char_type>(), const T, T>;
+    // format must be const for compatibility with std::format and compilation.
+    const auto& cf = f;
+    ctx.advance_to(cf.format(*static_cast<qualified_type*>(arg), ctx));
+  }
+};
 
-// Parses the range [begin, end) as an unsigned integer. This function assumes
-// that the range is non-empty and the first character is a digit.
-template <typename Char>
-FMT_CONSTEXPR auto parse_nonnegative_int(const Char*& begin, const Char* end,
-                                         int error_value) noexcept -> int {
-  FMT_ASSERT(begin != end && '0' <= *begin && *begin <= '9', "");
-  unsigned value = 0, prev = 0;
-  auto p = begin;
-  do {
-    prev = value;
-    value = value * 10 + unsigned(*p - '0');
-    ++p;
-  } while (p != end && '0' <= *p && *p <= '9');
-  auto num_digits = p - begin;
-  begin = p;
-  int digits10 = static_cast<int>(sizeof(int) * CHAR_BIT * 3 / 10);
-  if (num_digits <= digits10) return static_cast<int>(value);
-  // Check for overflow.
-  unsigned max = INT_MAX;
-  return num_digits == digits10 + 1 &&
-                 prev * 10ull + unsigned(p[-1] - '0') <= max
-             ? static_cast<int>(value)
-             : error_value;
+enum { packed_arg_bits = 4 };
+// Maximum number of arguments with packed types.
+enum { max_packed_args = 62 / packed_arg_bits };
+enum : unsigned long long { is_unpacked_bit = 1ULL << 63 };
+enum : unsigned long long { has_named_args_bit = 1ULL << 62 };
+
+template <typename It, typename T, typename Enable = void>
+struct is_output_iterator : std::false_type {};
+
+template <> struct is_output_iterator<appender, char> : std::true_type {};
+
+template <typename It, typename T>
+struct is_output_iterator<
+    It, T,
+    enable_if_t<std::is_assignable<decltype(*std::declval<decay_t<It>&>()++),
+                                   T>::value>> : std::true_type {};
+
+template <typename> constexpr auto encode_types() -> unsigned long long {
+  return 0;
 }
 
-FMT_CONSTEXPR inline auto parse_align(char c) -> align_t {
-  switch (c) {
-  case '<':
-    return align::left;
-  case '>':
-    return align::right;
-  case '^':
-    return align::center;
-  }
-  return align::none;
+template <typename Context, typename First, typename... T>
+constexpr auto encode_types() -> unsigned long long {
+  return static_cast<unsigned>(stored_type_constant<First, Context>::value) |
+         (encode_types<Context, T...>() << packed_arg_bits);
 }
 
-template <typename Char> constexpr auto is_name_start(Char c) -> bool {
-  return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || c == '_';
+template <typename Context, typename... T, size_t NUM_ARGS = sizeof...(T)>
+constexpr auto make_descriptor() -> unsigned long long {
+  return NUM_ARGS <= max_packed_args ? encode_types<Context, T...>()
+                                     : is_unpacked_bit | NUM_ARGS;
 }
 
-template <typename Char, typename Handler>
-FMT_CONSTEXPR auto do_parse_arg_id(const Char* begin, const Char* end,
-                                   Handler&& handler) -> const Char* {
-  Char c = *begin;
-  if (c >= '0' && c <= '9') {
-    int index = 0;
-    if (c != '0')
-      index = parse_nonnegative_int(begin, end, INT_MAX);
-    else
-      ++begin;
-    if (begin == end || (*begin != '}' && *begin != ':'))
-      report_error("invalid format string");
-    else
-      handler.on_index(index);
-    return begin;
+template <typename Context, int NUM_ARGS>
+using arg_t = conditional_t<NUM_ARGS <= max_packed_args, value<Context>,
+                            basic_format_arg<Context>>;
+
+template <typename Context, int NUM_ARGS, int NUM_NAMED_ARGS,
+          unsigned long long DESC>
+struct named_arg_store {
+  // args_[0].named_args points to named_args to avoid bloating format_args.
+  arg_t<Context, NUM_ARGS> args[1u + NUM_ARGS];
+  named_arg_info<typename Context::char_type>
+      named_args[static_cast<size_t>(NUM_NAMED_ARGS)];
+
+  template <typename... T>
+  FMT_CONSTEXPR FMT_ALWAYS_INLINE named_arg_store(T&... values)
+      : args{{named_args, NUM_NAMED_ARGS}, values...} {
+    int arg_index = 0, named_arg_index = 0;
+    FMT_APPLY_VARIADIC(
+        init_named_arg(named_args, arg_index, named_arg_index, values));
   }
-  if (!is_name_start(c)) {
-    report_error("invalid format string");
-    return begin;
+
+  named_arg_store(named_arg_store&& rhs) {
+    args[0] = {named_args, NUM_NAMED_ARGS};
+    for (size_t i = 1; i < sizeof(args) / sizeof(*args); ++i)
+      args[i] = rhs.args[i];
+    for (size_t i = 0; i < NUM_NAMED_ARGS; ++i)
+      named_args[i] = rhs.named_args[i];
   }
-  auto it = begin;
-  do {
-    ++it;
-  } while (it != end && (is_name_start(*it) || ('0' <= *it && *it <= '9')));
-  handler.on_name({begin, to_unsigned(it - begin)});
-  return it;
-}
 
-template <typename Char, typename Handler>
-FMT_CONSTEXPR auto parse_arg_id(const Char* begin, const Char* end,
-                                Handler&& handler) -> const Char* {
-  FMT_ASSERT(begin != end, "");
-  Char c = *begin;
-  if (c != '}' && c != ':') return do_parse_arg_id(begin, end, handler);
-  handler.on_auto();
-  return begin;
-}
+  named_arg_store(const named_arg_store& rhs) = delete;
+  auto operator=(const named_arg_store& rhs) -> named_arg_store& = delete;
+  auto operator=(named_arg_store&& rhs) -> named_arg_store& = delete;
+  operator const arg_t<Context, NUM_ARGS>*() const { return args + 1; }
+};
 
-template <typename Char> struct dynamic_spec_id_handler {
-  basic_format_parse_context<Char>& ctx;
-  arg_ref<Char>& ref;
+// An array of references to arguments. It can be implicitly converted to
+// `basic_format_args` for passing into type-erased formatting functions
+// such as `vformat`. It is a plain struct to reduce binary size in debug mode.
+template <typename Context, int NUM_ARGS, int NUM_NAMED_ARGS,
+          unsigned long long DESC>
+struct format_arg_store {
+  // +1 to workaround a bug in gcc 7.5 that causes duplicated-branches warning.
+  using type =
+      conditional_t<NUM_NAMED_ARGS == 0,
+                    arg_t<Context, NUM_ARGS>[max_of<size_t>(1, NUM_ARGS)],
+                    named_arg_store<Context, NUM_ARGS, NUM_NAMED_ARGS, DESC>>;
+  type args;
+};
 
-  FMT_CONSTEXPR void on_auto() {
-    int id = ctx.next_arg_id();
-    ref = arg_ref<Char>(id);
-    ctx.check_dynamic_spec(id);
-  }
-  FMT_CONSTEXPR void on_index(int id) {
-    ref = arg_ref<Char>(id);
-    ctx.check_arg_id(id);
-    ctx.check_dynamic_spec(id);
+// TYPE can be different from type_constant<T>, e.g. for __float128.
+template <typename T, typename Char, type TYPE> struct native_formatter {
+ private:
+  dynamic_format_specs<Char> specs_;
+
+ public:
+  using nonlocking = void;
+
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+    if (ctx.begin() == ctx.end() || *ctx.begin() == '}') return ctx.begin();
+    auto end = parse_format_specs(ctx.begin(), ctx.end(), specs_, ctx, TYPE);
+    if (const_check(TYPE == type::char_type)) check_char_specs(specs_);
+    return end;
   }
-  FMT_CONSTEXPR void on_name(basic_string_view<Char> id) {
-    ref = arg_ref<Char>(id);
-    ctx.check_arg_id(id);
+
+  template <type U = TYPE,
+            FMT_ENABLE_IF(U == type::string_type || U == type::cstring_type ||
+                          U == type::char_type)>
+  FMT_CONSTEXPR void set_debug_format(bool set = true) {
+    specs_.set_type(set ? presentation_type::debug : presentation_type::none);
   }
+
+  FMT_PRAGMA_CLANG(diagnostic ignored "-Wundefined-inline")
+  template <typename FormatContext>
+  FMT_CONSTEXPR auto format(const T& val, FormatContext& ctx) const
+      -> decltype(ctx.out());
 };
 
-// Parses [integer | "{" [arg_id] "}"].
+template <typename T, typename Enable = void>
+struct locking
+    : bool_constant<mapped_type_constant<T>::value == type::custom_type> {};
+template <typename T>
+struct locking<T, void_t<typename formatter<remove_cvref_t<T>>::nonlocking>>
+    : std::false_type {};
+
+template <typename T = int> FMT_CONSTEXPR inline auto is_locking() -> bool {
+  return locking<T>::value;
+}
+template <typename T1, typename T2, typename... Tail>
+FMT_CONSTEXPR inline auto is_locking() -> bool {
+  return locking<T1>::value || is_locking<T2, Tail...>();
+}
+
+FMT_API void vformat_to(buffer<char>& buf, string_view fmt, format_args args,
+                        locale_ref loc = {});
+
+#if FMT_WIN32
+FMT_API void vprint_mojibake(FILE*, string_view, format_args, bool);
+#else  // format_args is passed by reference since it is defined later.
+inline void vprint_mojibake(FILE*, string_view, const format_args&, bool) {}
+#endif
+}  // namespace detail
+
+// The main public API.
+
 template <typename Char>
-FMT_CONSTEXPR auto parse_dynamic_spec(const Char* begin, const Char* end,
-                                      int& value, arg_ref<Char>& ref,
-                                      basic_format_parse_context<Char>& ctx)
-    -> const Char* {
-  FMT_ASSERT(begin != end, "");
-  if ('0' <= *begin && *begin <= '9') {
-    int val = parse_nonnegative_int(begin, end, -1);
-    if (val != -1)
-      value = val;
-    else
-      report_error("number is too big");
-  } else if (*begin == '{') {
-    ++begin;
-    auto handler = dynamic_spec_id_handler<Char>{ctx, ref};
-    if (begin != end) begin = parse_arg_id(begin, end, handler);
-    if (begin != end && *begin == '}') return ++begin;
-    report_error("invalid format string");
+FMT_CONSTEXPR void parse_context<Char>::do_check_arg_id(int arg_id) {
+  // Argument id is only checked at compile time during parsing because
+  // formatting has its own validation.
+  if (detail::is_constant_evaluated() && use_constexpr_cast) {
+    auto ctx = static_cast<detail::compile_parse_context<Char>*>(this);
+    if (arg_id >= ctx->num_args()) report_error("argument not found");
   }
-  return begin;
 }
 
 template <typename Char>
-FMT_CONSTEXPR auto parse_precision(const Char* begin, const Char* end,
-                                   int& value, arg_ref<Char>& ref,
-                                   basic_format_parse_context<Char>& ctx)
-    -> const Char* {
-  ++begin;
-  if (begin == end || *begin == '}') {
-    report_error("invalid precision");
-    return begin;
-  }
-  return parse_dynamic_spec(begin, end, value, ref, ctx);
+FMT_CONSTEXPR void parse_context<Char>::check_dynamic_spec(int arg_id) {
+  using detail::compile_parse_context;
+  if (detail::is_constant_evaluated() && use_constexpr_cast)
+    static_cast<compile_parse_context<Char>*>(this)->check_dynamic_spec(arg_id);
 }
 
-enum class state { start, align, sign, hash, zero, width, precision, locale };
+FMT_BEGIN_EXPORT
 
-// Parses standard format specifiers.
-template <typename Char>
-FMT_CONSTEXPR auto parse_format_specs(const Char* begin, const Char* end,
-                                      dynamic_format_specs<Char>& specs,
-                                      basic_format_parse_context<Char>& ctx,
-                                      type arg_type) -> const Char* {
-  auto c = '\0';
-  if (end - begin > 1) {
-    auto next = to_ascii(begin[1]);
-    c = parse_align(next) == align::none ? to_ascii(*begin) : '\0';
-  } else {
-    if (begin == end) return begin;
-    c = to_ascii(*begin);
+// An output iterator that appends to a buffer. It is used instead of
+// back_insert_iterator to reduce symbol sizes and avoid <iterator> dependency.
+template <typename T> class basic_appender {
+ protected:
+  detail::buffer<T>* container;
+
+ public:
+  using container_type = detail::buffer<T>;
+
+  FMT_CONSTEXPR basic_appender(detail::buffer<T>& buf) : container(&buf) {}
+
+  FMT_CONSTEXPR20 auto operator=(T c) -> basic_appender& {
+    container->push_back(c);
+    return *this;
   }
+  FMT_CONSTEXPR20 auto operator*() -> basic_appender& { return *this; }
+  FMT_CONSTEXPR20 auto operator++() -> basic_appender& { return *this; }
+  FMT_CONSTEXPR20 auto operator++(int) -> basic_appender { return *this; }
+};
 
-  struct {
-    state current_state = state::start;
-    FMT_CONSTEXPR void operator()(state s, bool valid = true) {
-      if (current_state >= s || !valid)
-        report_error("invalid format specifier");
-      current_state = s;
-    }
-  } enter_state;
+// A formatting argument. Context is a template parameter for the compiled API
+// where output can be unbuffered.
+template <typename Context> class basic_format_arg {
+ private:
+  detail::value<Context> value_;
+  detail::type type_;
 
-  using pres = presentation_type;
-  constexpr auto integral_set = sint_set | uint_set | bool_set | char_set;
-  struct {
-    const Char*& begin;
-    dynamic_format_specs<Char>& specs;
-    type arg_type;
+  friend class basic_format_args<Context>;
 
-    FMT_CONSTEXPR auto operator()(pres pres_type, int set) -> const Char* {
-      if (!in(arg_type, set)) {
-        if (arg_type == type::none_type) return begin;
-        report_error("invalid format specifier");
-      }
-      specs.type = pres_type;
-      return begin + 1;
-    }
-  } parse_presentation_type{begin, specs, arg_type};
+  using char_type = typename Context::char_type;
 
-  for (;;) {
-    switch (c) {
-    case '<':
-    case '>':
-    case '^':
-      enter_state(state::align);
-      specs.align = parse_align(c);
-      ++begin;
-      break;
-    case '+':
-    case '-':
-    case ' ':
-      if (arg_type == type::none_type) return begin;
-      enter_state(state::sign, in(arg_type, sint_set | float_set));
-      switch (c) {
-      case '+':
-        specs.sign = sign::plus;
-        break;
-      case '-':
-        specs.sign = sign::minus;
-        break;
-      case ' ':
-        specs.sign = sign::space;
-        break;
-      }
-      ++begin;
-      break;
-    case '#':
-      if (arg_type == type::none_type) return begin;
-      enter_state(state::hash, is_arithmetic_type(arg_type));
-      specs.alt = true;
-      ++begin;
-      break;
-    case '0':
-      enter_state(state::zero);
-      if (!is_arithmetic_type(arg_type)) {
-        if (arg_type == type::none_type) return begin;
-        report_error("format specifier requires numeric argument");
-      }
-      if (specs.align == align::none) {
-        // Ignore 0 if align is specified for compatibility with std::format.
-        specs.align = align::numeric;
-        specs.fill = '0';
-      }
-      ++begin;
-      break;
-    case '1':
-    case '2':
-    case '3':
-    case '4':
-    case '5':
-    case '6':
-    case '7':
-    case '8':
-    case '9':
-    case '{':
-      enter_state(state::width);
-      begin = parse_dynamic_spec(begin, end, specs.width, specs.width_ref, ctx);
-      break;
-    case '.':
-      if (arg_type == type::none_type) return begin;
-      enter_state(state::precision,
-                  in(arg_type, float_set | string_set | cstring_set));
-      begin = parse_precision(begin, end, specs.precision, specs.precision_ref,
-                              ctx);
-      break;
-    case 'L':
-      if (arg_type == type::none_type) return begin;
-      enter_state(state::locale, is_arithmetic_type(arg_type));
-      specs.localized = true;
-      ++begin;
-      break;
-    case 'd':
-      return parse_presentation_type(pres::dec, integral_set);
-    case 'X':
-      specs.upper = true;
-      FMT_FALLTHROUGH;
-    case 'x':
-      return parse_presentation_type(pres::hex, integral_set);
-    case 'o':
-      return parse_presentation_type(pres::oct, integral_set);
-    case 'B':
-      specs.upper = true;
-      FMT_FALLTHROUGH;
-    case 'b':
-      return parse_presentation_type(pres::bin, integral_set);
-    case 'E':
-      specs.upper = true;
-      FMT_FALLTHROUGH;
-    case 'e':
-      return parse_presentation_type(pres::exp, float_set);
-    case 'F':
-      specs.upper = true;
-      FMT_FALLTHROUGH;
-    case 'f':
-      return parse_presentation_type(pres::fixed, float_set);
-    case 'G':
-      specs.upper = true;
-      FMT_FALLTHROUGH;
-    case 'g':
-      return parse_presentation_type(pres::general, float_set);
-    case 'A':
-      specs.upper = true;
-      FMT_FALLTHROUGH;
-    case 'a':
-      return parse_presentation_type(pres::hexfloat, float_set);
-    case 'c':
-      if (arg_type == type::bool_type) report_error("invalid format specifier");
-      return parse_presentation_type(pres::chr, integral_set);
-    case 's':
-      return parse_presentation_type(pres::string,
-                                     bool_set | string_set | cstring_set);
-    case 'p':
-      return parse_presentation_type(pres::pointer, pointer_set | cstring_set);
-    case '?':
-      return parse_presentation_type(pres::debug,
-                                     char_set | string_set | cstring_set);
-    case '}':
-      return begin;
-    default: {
-      if (*begin == '}') return begin;
-      // Parse fill and alignment.
-      auto fill_end = begin + code_point_length(begin);
-      if (end - fill_end <= 0) {
-        report_error("invalid format specifier");
-        return begin;
-      }
-      if (*begin == '{') {
-        report_error("invalid fill character '{'");
-        return begin;
-      }
-      auto align = parse_align(to_ascii(*fill_end));
-      enter_state(state::align, align != align::none);
-      specs.fill =
-          basic_string_view<Char>(begin, to_unsigned(fill_end - begin));
-      specs.align = align;
-      begin = fill_end + 1;
-    }
-    }
-    if (begin == end) return begin;
-    c = to_ascii(*begin);
-  }
-}
+ public:
+  class handle {
+   private:
+    detail::custom_value<Context> custom_;
+
+   public:
+    explicit handle(detail::custom_value<Context> custom) : custom_(custom) {}
 
-template <typename Char, typename Handler>
-FMT_CONSTEXPR auto parse_replacement_field(const Char* begin, const Char* end,
-                                           Handler&& handler) -> const Char* {
-  struct id_adapter {
-    Handler& handler;
-    int arg_id;
-
-    FMT_CONSTEXPR void on_auto() { arg_id = handler.on_arg_id(); }
-    FMT_CONSTEXPR void on_index(int id) { arg_id = handler.on_arg_id(id); }
-    FMT_CONSTEXPR void on_name(basic_string_view<Char> id) {
-      arg_id = handler.on_arg_id(id);
+    void format(parse_context<char_type>& parse_ctx, Context& ctx) const {
+      custom_.format(custom_.value, parse_ctx, ctx);
     }
   };
 
-  ++begin;
-  if (begin == end) return handler.on_error("invalid format string"), end;
-  if (*begin == '}') {
-    handler.on_replacement_field(handler.on_arg_id(), begin);
-  } else if (*begin == '{') {
-    handler.on_text(begin, begin + 1);
-  } else {
-    auto adapter = id_adapter{handler, 0};
-    begin = parse_arg_id(begin, end, adapter);
-    Char c = begin != end ? *begin : Char();
-    if (c == '}') {
-      handler.on_replacement_field(adapter.arg_id, begin);
-    } else if (c == ':') {
-      begin = handler.on_format_specs(adapter.arg_id, begin + 1, end);
-      if (begin == end || *begin != '}')
-        return handler.on_error("unknown format specifier"), end;
-    } else {
-      return handler.on_error("missing '}' in format string"), end;
-    }
+  constexpr basic_format_arg() : type_(detail::type::none_type) {}
+  basic_format_arg(const detail::named_arg_info<char_type>* args, size_t size)
+      : value_(args, size) {}
+  template <typename T>
+  basic_format_arg(T&& val)
+      : value_(val), type_(detail::stored_type_constant<T, Context>::value) {}
+
+  constexpr explicit operator bool() const noexcept {
+    return type_ != detail::type::none_type;
   }
-  return begin + 1;
-}
+  auto type() const -> detail::type { return type_; }
 
-template <bool IS_CONSTEXPR, typename Char, typename Handler>
-FMT_CONSTEXPR void parse_format_string(basic_string_view<Char> format_str,
-                                       Handler&& handler) {
-  auto begin = format_str.data();
-  auto end = begin + format_str.size();
-  if (end - begin < 32) {
-    // Use a simple loop instead of memchr for small strings.
-    const Char* p = begin;
-    while (p != end) {
-      auto c = *p++;
-      if (c == '{') {
-        handler.on_text(begin, p - 1);
-        begin = p = parse_replacement_field(p - 1, end, handler);
-      } else if (c == '}') {
-        if (p == end || *p != '}')
-          return handler.on_error("unmatched '}' in format string");
-        handler.on_text(begin, p);
-        begin = ++p;
-      }
-    }
-    handler.on_text(begin, end);
-    return;
-  }
-  struct writer {
-    FMT_CONSTEXPR void operator()(const Char* from, const Char* to) {
-      if (from == to) return;
-      for (;;) {
-        const Char* p = nullptr;
-        if (!find<IS_CONSTEXPR>(from, to, Char('}'), p))
-          return handler_.on_text(from, to);
-        ++p;
-        if (p == to || *p != '}')
-          return handler_.on_error("unmatched '}' in format string");
-        handler_.on_text(from, p);
-        from = p + 1;
-      }
+  /**
+   * Visits an argument dispatching to the appropriate visit method based on
+   * the argument type. For example, if the argument type is `double` then
+   * `vis(value)` will be called with the value of type `double`.
+   */
+  template <typename Visitor>
+  FMT_CONSTEXPR FMT_INLINE auto visit(Visitor&& vis) const -> decltype(vis(0)) {
+    using detail::map;
+    switch (type_) {
+    case detail::type::none_type:        break;
+    case detail::type::int_type:         return vis(value_.int_value);
+    case detail::type::uint_type:        return vis(value_.uint_value);
+    case detail::type::long_long_type:   return vis(value_.long_long_value);
+    case detail::type::ulong_long_type:  return vis(value_.ulong_long_value);
+    case detail::type::int128_type:      return vis(map(value_.int128_value));
+    case detail::type::uint128_type:     return vis(map(value_.uint128_value));
+    case detail::type::bool_type:        return vis(value_.bool_value);
+    case detail::type::char_type:        return vis(value_.char_value);
+    case detail::type::float_type:       return vis(value_.float_value);
+    case detail::type::double_type:      return vis(value_.double_value);
+    case detail::type::long_double_type: return vis(value_.long_double_value);
+    case detail::type::cstring_type:     return vis(value_.string.data);
+    case detail::type::string_type:      return vis(value_.string.str());
+    case detail::type::pointer_type:     return vis(value_.pointer);
+    case detail::type::custom_type:      return vis(handle(value_.custom));
     }
-    Handler& handler_;
-  } write = {handler};
-  while (begin != end) {
-    // Doing two passes with memchr (one for '{' and another for '}') is up to
-    // 2.5x faster than the naive one-pass implementation on big format strings.
-    const Char* p = begin;
-    if (*begin != '{' && !find<IS_CONSTEXPR>(begin + 1, end, Char('{'), p))
-      return write(begin, end);
-    write(begin, p);
-    begin = parse_replacement_field(p, end, handler);
+    return vis(monostate());
   }
-}
 
-template <typename T, bool = is_named_arg<T>::value> struct strip_named_arg {
-  using type = T;
-};
-template <typename T> struct strip_named_arg<T, true> {
-  using type = remove_cvref_t<decltype(T::value)>;
+  auto format_custom(const char_type* parse_begin,
+                     parse_context<char_type>& parse_ctx, Context& ctx)
+      -> bool {
+    if (type_ != detail::type::custom_type) return false;
+    parse_ctx.advance_to(parse_begin);
+    value_.custom.format(value_.custom.value, parse_ctx, ctx);
+    return true;
+  }
 };
 
-template <typename T, typename ParseContext>
-FMT_VISIBILITY("hidden")  // Suppress an ld warning on macOS (#3769).
-FMT_CONSTEXPR auto parse_format_specs(ParseContext& ctx)
-    -> decltype(ctx.begin()) {
-  using char_type = typename ParseContext::char_type;
-  using context = buffered_context<char_type>;
-  using mapped_type = conditional_t<
-      mapped_type_constant<T, context>::value != type::custom_type,
-      decltype(arg_mapper<context>().map(std::declval<const T&>())),
-      typename strip_named_arg<T>::type>;
-#if defined(__cpp_if_constexpr)
-  if constexpr (std::is_default_constructible<
-                    formatter<mapped_type, char_type>>::value) {
-    return formatter<mapped_type, char_type>().parse(ctx);
-  } else {
-    type_is_unformattable_for<T, char_type> _;
-    return ctx.begin();
-  }
-#else
-  return formatter<mapped_type, char_type>().parse(ctx);
-#endif
-}
+/**
+ * A view of a collection of formatting arguments. To avoid lifetime issues it
+ * should only be used as a parameter type in type-erased functions such as
+ * `vformat`:
+ *
+ *     void vlog(fmt::string_view fmt, fmt::format_args args);  // OK
+ *     fmt::format_args args = fmt::make_format_args();  // Dangling reference
+ */
+template <typename Context> class basic_format_args {
+ private:
+  // A descriptor that contains information about formatting arguments.
+  // If the number of arguments is less or equal to max_packed_args then
+  // argument types are passed in the descriptor. This reduces binary code size
+  // per formatting function call.
+  unsigned long long desc_;
+  union {
+    // If is_packed() returns true then argument values are stored in values_;
+    // otherwise they are stored in args_. This is done to improve cache
+    // locality and reduce compiled code size since storing larger objects
+    // may require more code (at least on x86-64) even if the same amount of
+    // data is actually copied to stack. It saves ~10% on the bloat test.
+    const detail::value<Context>* values_;
+    const basic_format_arg<Context>* args_;
+  };
 
-// Checks char specs and returns true iff the presentation type is char-like.
-FMT_CONSTEXPR inline auto check_char_specs(const format_specs& specs) -> bool {
-  if (specs.type != presentation_type::none &&
-      specs.type != presentation_type::chr &&
-      specs.type != presentation_type::debug) {
-    return false;
+  constexpr auto is_packed() const -> bool {
+    return (desc_ & detail::is_unpacked_bit) == 0;
+  }
+  constexpr auto has_named_args() const -> bool {
+    return (desc_ & detail::has_named_args_bit) != 0;
   }
-  if (specs.align == align::numeric || specs.sign != sign::none || specs.alt)
-    report_error("invalid format specifier for char");
-  return true;
-}
 
-#if FMT_USE_NONTYPE_TEMPLATE_ARGS
-template <int N, typename T, typename... Args, typename Char>
-constexpr auto get_arg_index_by_name(basic_string_view<Char> name) -> int {
-  if constexpr (is_statically_named_arg<T>()) {
-    if (name == T::name) return N;
+  FMT_CONSTEXPR auto type(int index) const -> detail::type {
+    int shift = index * detail::packed_arg_bits;
+    unsigned mask = (1 << detail::packed_arg_bits) - 1;
+    return static_cast<detail::type>((desc_ >> shift) & mask);
   }
-  if constexpr (sizeof...(Args) > 0)
-    return get_arg_index_by_name<N + 1, Args...>(name);
-  (void)name;  // Workaround an MSVC bug about "unused" parameter.
-  return -1;
-}
-#endif
 
-template <typename... Args, typename Char>
-FMT_CONSTEXPR auto get_arg_index_by_name(basic_string_view<Char> name) -> int {
-#if FMT_USE_NONTYPE_TEMPLATE_ARGS
-  if constexpr (sizeof...(Args) > 0)
-    return get_arg_index_by_name<0, Args...>(name);
-#endif
-  (void)name;
-  return -1;
-}
+  template <int NUM_ARGS, int NUM_NAMED_ARGS, unsigned long long DESC>
+  using store =
+      detail::format_arg_store<Context, NUM_ARGS, NUM_NAMED_ARGS, DESC>;
 
-template <typename Char, typename... Args> class format_string_checker {
- private:
-  using parse_context_type = compile_parse_context<Char>;
-  static constexpr int num_args = sizeof...(Args);
+ public:
+  using format_arg = basic_format_arg<Context>;
 
-  // Format specifier parsing function.
-  // In the future basic_format_parse_context will replace compile_parse_context
-  // here and will use is_constant_evaluated and downcasting to access the data
-  // needed for compile-time checks: https://godbolt.org/z/GvWzcTjh1.
-  using parse_func = const Char* (*)(parse_context_type&);
+  constexpr basic_format_args() : desc_(0), args_(nullptr) {}
 
-  type types_[num_args > 0 ? static_cast<size_t>(num_args) : 1];
-  parse_context_type context_;
-  parse_func parse_funcs_[num_args > 0 ? static_cast<size_t>(num_args) : 1];
+  /// Constructs a `basic_format_args` object from `format_arg_store`.
+  template <int NUM_ARGS, int NUM_NAMED_ARGS, unsigned long long DESC,
+            FMT_ENABLE_IF(NUM_ARGS <= detail::max_packed_args)>
+  constexpr FMT_ALWAYS_INLINE basic_format_args(
+      const store<NUM_ARGS, NUM_NAMED_ARGS, DESC>& s)
+      : desc_(DESC | (NUM_NAMED_ARGS != 0 ? +detail::has_named_args_bit : 0)),
+        values_(s.args) {}
 
- public:
-  explicit FMT_CONSTEXPR format_string_checker(basic_string_view<Char> fmt)
-      : types_{mapped_type_constant<Args, buffered_context<Char>>::value...},
-        context_(fmt, num_args, types_),
-        parse_funcs_{&parse_format_specs<Args, parse_context_type>...} {}
+  template <int NUM_ARGS, int NUM_NAMED_ARGS, unsigned long long DESC,
+            FMT_ENABLE_IF(NUM_ARGS > detail::max_packed_args)>
+  constexpr basic_format_args(const store<NUM_ARGS, NUM_NAMED_ARGS, DESC>& s)
+      : desc_(DESC | (NUM_NAMED_ARGS != 0 ? +detail::has_named_args_bit : 0)),
+        args_(s.args) {}
 
-  FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
+  /// Constructs a `basic_format_args` object from a dynamic list of arguments.
+  constexpr basic_format_args(const format_arg* args, int count,
+                              bool has_named = false)
+      : desc_(detail::is_unpacked_bit | detail::to_unsigned(count) |
+              (has_named ? +detail::has_named_args_bit : 0)),
+        args_(args) {}
 
-  FMT_CONSTEXPR auto on_arg_id() -> int { return context_.next_arg_id(); }
-  FMT_CONSTEXPR auto on_arg_id(int id) -> int {
-    return context_.check_arg_id(id), id;
-  }
-  FMT_CONSTEXPR auto on_arg_id(basic_string_view<Char> id) -> int {
-#if FMT_USE_NONTYPE_TEMPLATE_ARGS
-    auto index = get_arg_index_by_name<Args...>(id);
-    if (index < 0) on_error("named argument is not found");
-    return index;
-#else
-    (void)id;
-    on_error("compile-time checks for named arguments require C++20 support");
-    return 0;
-#endif
+  /// Returns the argument with the specified id.
+  FMT_CONSTEXPR auto get(int id) const -> format_arg {
+    auto arg = format_arg();
+    if (!is_packed()) {
+      if (id < max_size()) arg = args_[id];
+      return arg;
+    }
+    if (static_cast<unsigned>(id) >= detail::max_packed_args) return arg;
+    arg.type_ = type(id);
+    if (arg.type_ != detail::type::none_type) arg.value_ = values_[id];
+    return arg;
   }
 
-  FMT_CONSTEXPR void on_replacement_field(int id, const Char* begin) {
-    on_format_specs(id, begin, begin);  // Call parse() on empty specs.
+  template <typename Char>
+  auto get(basic_string_view<Char> name) const -> format_arg {
+    int id = get_id(name);
+    return id >= 0 ? get(id) : format_arg();
   }
 
-  FMT_CONSTEXPR auto on_format_specs(int id, const Char* begin, const Char*)
-      -> const Char* {
-    context_.advance_to(begin);
-    // id >= 0 check is a workaround for gcc 10 bug (#2065).
-    return id >= 0 && id < num_args ? parse_funcs_[id](context_) : begin;
+  template <typename Char>
+  FMT_CONSTEXPR auto get_id(basic_string_view<Char> name) const -> int {
+    if (!has_named_args()) return -1;
+    const auto& named_args =
+        (is_packed() ? values_[-1] : args_[-1].value_).named_args;
+    for (size_t i = 0; i < named_args.size; ++i) {
+      if (named_args.data[i].name == name) return named_args.data[i].id;
+    }
+    return -1;
   }
 
-  FMT_NORETURN FMT_CONSTEXPR void on_error(const char* message) {
-    report_error(message);
+  auto max_size() const -> int {
+    unsigned long long max_packed = detail::max_packed_args;
+    return static_cast<int>(is_packed() ? max_packed
+                                        : desc_ & ~detail::is_unpacked_bit);
   }
 };
 
-// A base class for compile-time strings.
-struct compile_string {};
+// A formatting context.
+class context {
+ private:
+  appender out_;
+  format_args args_;
+  FMT_NO_UNIQUE_ADDRESS locale_ref loc_;
 
-template <typename S>
-using is_compile_string = std::is_base_of<compile_string, S>;
+ public:
+  using char_type = char;  ///< The character type for the output.
+  using iterator = appender;
+  using format_arg = basic_format_arg<context>;
+  enum { builtin_types = FMT_BUILTIN_TYPES };
 
-// Reports a compile-time error if S is not a valid format string.
-template <typename..., typename S, FMT_ENABLE_IF(!is_compile_string<S>::value)>
-FMT_ALWAYS_INLINE void check_format_string(const S&) {
-#ifdef FMT_ENFORCE_COMPILE_STRING
-  static_assert(is_compile_string<S>::value,
-                "FMT_ENFORCE_COMPILE_STRING requires all format strings to use "
-                "FMT_STRING.");
-#endif
-}
-template <typename... Args, typename S,
-          FMT_ENABLE_IF(is_compile_string<S>::value)>
-void check_format_string(S format_str) {
-  using char_t = typename S::char_type;
-  FMT_CONSTEXPR auto s = basic_string_view<char_t>(format_str);
-  using checker = format_string_checker<char_t, remove_cvref_t<Args>...>;
-  FMT_CONSTEXPR bool error = (parse_format_string<true>(s, checker(s)), true);
-  ignore_unused(error);
-}
+  /// Constructs a `context` object. References to the arguments are stored
+  /// in the object so make sure they have appropriate lifetimes.
+  FMT_CONSTEXPR context(iterator out, format_args args, locale_ref loc = {})
+      : out_(out), args_(args), loc_(loc) {}
+  context(context&&) = default;
+  context(const context&) = delete;
+  void operator=(const context&) = delete;
 
-// Report truncation to prevent silent data loss.
-inline void report_truncation(bool truncated) {
-  if (truncated) report_error("output is truncated");
-}
+  FMT_CONSTEXPR auto arg(int id) const -> format_arg { return args_.get(id); }
+  inline auto arg(string_view name) const -> format_arg {
+    return args_.get(name);
+  }
+  FMT_CONSTEXPR auto arg_id(string_view name) const -> int {
+    return args_.get_id(name);
+  }
+  auto args() const -> const format_args& { return args_; }
 
-// Use vformat_args and avoid type_identity to keep symbols short and workaround
-// a GCC <= 4.8 bug.
-template <typename Char = char> struct vformat_args {
-  using type = basic_format_args<buffered_context<Char>>;
-};
-template <> struct vformat_args<char> {
-  using type = format_args;
+  // Returns an iterator to the beginning of the output range.
+  FMT_CONSTEXPR auto out() const -> iterator { return out_; }
+
+  // Advances the begin iterator to `it`.
+  FMT_CONSTEXPR void advance_to(iterator) {}
+
+  FMT_CONSTEXPR auto locale() const -> locale_ref { return loc_; }
 };
 
-template <typename Char>
-void vformat_to(buffer<Char>& buf, basic_string_view<Char> fmt,
-                typename vformat_args<Char>::type args, locale_ref loc = {});
+template <typename Char = char> struct runtime_format_string {
+  basic_string_view<Char> str;
+};
 
-FMT_API void vprint_mojibake(FILE*, string_view, format_args, bool = false);
-#ifndef _WIN32
-inline void vprint_mojibake(FILE*, string_view, format_args, bool) {}
-#endif
+/**
+ * Creates a runtime format string.
+ *
+ * **Example**:
+ *
+ *     // Check format string at runtime instead of compile-time.
+ *     fmt::print(fmt::runtime("{:d}"), "I am not a number");
+ */
+inline auto runtime(string_view s) -> runtime_format_string<> { return {{s}}; }
 
-template <typename T, typename Char, type TYPE> struct native_formatter {
+/// A compile-time format string. Use `format_string` in the public API to
+/// prevent type deduction.
+template <typename... T> struct fstring {
  private:
-  dynamic_format_specs<Char> specs_;
+  static constexpr int num_static_named_args =
+      detail::count_static_named_args<T...>();
 
- public:
-  using nonlocking = void;
+  using checker = detail::format_string_checker<
+      char, static_cast<int>(sizeof...(T)), num_static_named_args,
+      num_static_named_args != detail::count_named_args<T...>()>;
 
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> const Char* {
-    if (ctx.begin() == ctx.end() || *ctx.begin() == '}') return ctx.begin();
-    auto end = parse_format_specs(ctx.begin(), ctx.end(), specs_, ctx, TYPE);
-    if (const_check(TYPE == type::char_type)) check_char_specs(specs_);
-    return end;
-  }
+  using arg_pack = detail::arg_pack<T...>;
 
-  template <type U = TYPE,
-            FMT_ENABLE_IF(U == type::string_type || U == type::cstring_type ||
-                          U == type::char_type)>
-  FMT_CONSTEXPR void set_debug_format(bool set = true) {
-    specs_.type = set ? presentation_type::debug : presentation_type::none;
+ public:
+  string_view str;
+  using t = fstring;
+
+  // Reports a compile-time error if S is not a valid format string for T.
+  template <size_t N>
+  FMT_CONSTEVAL FMT_ALWAYS_INLINE fstring(const char (&s)[N]) : str(s, N - 1) {
+    using namespace detail;
+    static_assert(count<(is_view<remove_cvref_t<T>>::value &&
+                         std::is_reference<T>::value)...>() == 0,
+                  "passing views as lvalues is disallowed");
+    if (FMT_USE_CONSTEVAL) parse_format_string<char>(s, checker(s, arg_pack()));
+#ifdef FMT_ENFORCE_COMPILE_STRING
+    static_assert(
+        FMT_USE_CONSTEVAL && sizeof(s) != 0,
+        "FMT_ENFORCE_COMPILE_STRING requires format strings to use FMT_STRING");
+#endif
   }
-
-  template <typename FormatContext>
-  FMT_CONSTEXPR auto format(const T& val, FormatContext& ctx) const
-      -> decltype(ctx.out());
+  template <typename S,
+            FMT_ENABLE_IF(std::is_convertible<const S&, string_view>::value)>
+  FMT_CONSTEVAL FMT_ALWAYS_INLINE fstring(const S& s) : str(s) {
+    auto sv = string_view(str);
+    if (FMT_USE_CONSTEVAL)
+      detail::parse_format_string<char>(sv, checker(sv, arg_pack()));
+#ifdef FMT_ENFORCE_COMPILE_STRING
+    static_assert(
+        FMT_USE_CONSTEVAL && sizeof(s) != 0,
+        "FMT_ENFORCE_COMPILE_STRING requires format strings to use FMT_STRING");
+#endif
+  }
+  template <typename S,
+            FMT_ENABLE_IF(std::is_base_of<detail::compile_string, S>::value&&
+                              std::is_same<typename S::char_type, char>::value)>
+  FMT_ALWAYS_INLINE fstring(const S&) : str(S()) {
+    FMT_CONSTEXPR auto sv = string_view(S());
+    FMT_CONSTEXPR int unused =
+        (parse_format_string(sv, checker(sv, arg_pack())), 0);
+    detail::ignore_unused(unused);
+  }
+  fstring(runtime_format_string<> fmt) : str(fmt.str) {}
+
+  // Returning by reference generates better code in debug mode.
+  FMT_ALWAYS_INLINE operator const string_view&() const { return str; }
+  auto get() const -> string_view { return str; }
 };
-}  // namespace detail
 
-FMT_BEGIN_EXPORT
+template <typename... T> using format_string = typename fstring<T...>::t;
+
+template <typename T, typename Char = char>
+using is_formattable = bool_constant<!std::is_same<
+    detail::mapped_t<conditional_t<std::is_void<T>::value, int*, T>, Char>,
+    void>::value>;
+#ifdef __cpp_concepts
+template <typename T, typename Char = char>
+concept formattable = is_formattable<remove_reference_t<T>, Char>::value;
+#endif
 
 // A formatter specialization for natively supported types.
 template <typename T, typename Char>
@@ -2838,62 +2810,42 @@ struct formatter<T, Char,
     : detail::native_formatter<T, Char, detail::type_constant<T, Char>::value> {
 };
 
-template <typename Char = char> struct runtime_format_string {
-  basic_string_view<Char> str;
-};
-
-/// A compile-time format string.
-template <typename Char, typename... Args> class basic_format_string {
- private:
-  basic_string_view<Char> str_;
-
- public:
-  template <
-      typename S,
-      FMT_ENABLE_IF(
-          std::is_convertible<const S&, basic_string_view<Char>>::value ||
-          (detail::is_compile_string<S>::value &&
-           std::is_constructible<basic_string_view<Char>, const S&>::value))>
-  FMT_CONSTEVAL FMT_ALWAYS_INLINE basic_format_string(const S& s) : str_(s) {
-    static_assert(
-        detail::count<
-            (std::is_base_of<detail::view, remove_reference_t<Args>>::value &&
-             std::is_reference<Args>::value)...>() == 0,
-        "passing views as lvalues is disallowed");
-#if FMT_USE_CONSTEVAL
-    if constexpr (detail::count_named_args<Args...>() ==
-                  detail::count_statically_named_args<Args...>()) {
-      using checker =
-          detail::format_string_checker<Char, remove_cvref_t<Args>...>;
-      detail::parse_format_string<true>(str_, checker(s));
-    }
-#else
-    detail::check_format_string<Args...>(s);
-#endif
-  }
-  basic_format_string(runtime_format_string<Char> fmt) : str_(fmt.str) {}
+/**
+ * Constructs an object that stores references to arguments and can be
+ * implicitly converted to `format_args`. `Context` can be omitted in which case
+ * it defaults to `context`. See `arg` for lifetime considerations.
+ */
+// Take arguments by lvalue references to avoid some lifetime issues, e.g.
+//   auto args = make_format_args(std::string());
+template <typename Context = context, typename... T,
+          int NUM_ARGS = sizeof...(T),
+          int NUM_NAMED_ARGS = detail::count_named_args<T...>(),
+          unsigned long long DESC = detail::make_descriptor<Context, T...>()>
+constexpr FMT_ALWAYS_INLINE auto make_format_args(T&... args)
+    -> detail::format_arg_store<Context, NUM_ARGS, NUM_NAMED_ARGS, DESC> {
+  // Suppress warnings for pathological types convertible to detail::value.
+  FMT_PRAGMA_GCC(diagnostic ignored "-Wconversion")
+  return {{args...}};
+}
 
-  FMT_ALWAYS_INLINE operator basic_string_view<Char>() const { return str_; }
-  auto get() const -> basic_string_view<Char> { return str_; }
-};
+template <typename... T>
+using vargs =
+    detail::format_arg_store<context, sizeof...(T),
+                             detail::count_named_args<T...>(),
+                             detail::make_descriptor<context, T...>()>;
 
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
-// Workaround broken conversion on older gcc.
-template <typename...> using format_string = string_view;
-inline auto runtime(string_view s) -> string_view { return s; }
-#else
-template <typename... Args>
-using format_string = basic_format_string<char, type_identity_t<Args>...>;
 /**
- * Creates a runtime format string.
+ * Returns a named argument to be used in a formatting function.
+ * It should only be used in a call to a formatting function.
  *
  * **Example**:
  *
- *     // Check format string at runtime instead of compile-time.
- *     fmt::print(fmt::runtime("{:d}"), "I am not a number");
+ *     fmt::print("The answer is {answer}.", fmt::arg("answer", 42));
  */
-inline auto runtime(string_view s) -> runtime_format_string<> { return {{s}}; }
-#endif
+template <typename Char, typename T>
+inline auto arg(const Char* name, const T& arg) -> detail::named_arg<Char, T> {
+  return {name, arg};
+}
 
 /// Formats a string and writes the output to `out`.
 template <typename OutputIt,
@@ -2921,7 +2873,7 @@ template <typename OutputIt, typename... T,
                                                    char>::value)>
 FMT_INLINE auto format_to(OutputIt&& out, format_string<T...> fmt, T&&... args)
     -> remove_cvref_t<OutputIt> {
-  return vformat_to(FMT_FWD(out), fmt, fmt::make_format_args(args...));
+  return vformat_to(out, fmt.str, vargs<T...>{{args...}});
 }
 
 template <typename OutputIt> struct format_to_n_result {
@@ -2951,41 +2903,33 @@ template <typename OutputIt, typename... T,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
 FMT_INLINE auto format_to_n(OutputIt out, size_t n, format_string<T...> fmt,
                             T&&... args) -> format_to_n_result<OutputIt> {
-  return vformat_to_n(out, n, fmt, fmt::make_format_args(args...));
+  return vformat_to_n(out, n, fmt.str, vargs<T...>{{args...}});
 }
 
-template <typename OutputIt, typename Sentinel = OutputIt>
 struct format_to_result {
-  /// Iterator pointing to just after the last successful write in the range.
-  OutputIt out;
+  /// Pointer to just after the last successful write in the array.
+  char* out;
   /// Specifies if the output was truncated.
   bool truncated;
 
-  FMT_CONSTEXPR operator OutputIt&() & {
-    detail::report_truncation(truncated);
-    return out;
-  }
-  FMT_CONSTEXPR operator const OutputIt&() const& {
-    detail::report_truncation(truncated);
+  FMT_CONSTEXPR operator char*() const {
+    // Report truncation to prevent silent data loss.
+    if (truncated) report_error("output is truncated");
     return out;
   }
-  FMT_CONSTEXPR operator OutputIt&&() && {
-    detail::report_truncation(truncated);
-    return static_cast<OutputIt&&>(out);
-  }
 };
 
 template <size_t N>
 auto vformat_to(char (&out)[N], string_view fmt, format_args args)
-    -> format_to_result<char*> {
+    -> format_to_result {
   auto result = vformat_to_n(out, N, fmt, args);
   return {result.out, result.size > N};
 }
 
 template <size_t N, typename... T>
 FMT_INLINE auto format_to(char (&out)[N], format_string<T...> fmt, T&&... args)
-    -> format_to_result<char*> {
-  auto result = fmt::format_to_n(out, N, fmt, static_cast<T&&>(args)...);
+    -> format_to_result {
+  auto result = vformat_to_n(out, N, fmt.str, vargs<T...>{{args...}});
   return {result.out, result.size > N};
 }
 
@@ -2994,14 +2938,14 @@ template <typename... T>
 FMT_NODISCARD FMT_INLINE auto formatted_size(format_string<T...> fmt,
                                              T&&... args) -> size_t {
   auto buf = detail::counting_buffer<>();
-  detail::vformat_to<char>(buf, fmt, fmt::make_format_args(args...), {});
+  detail::vformat_to(buf, fmt.str, vargs<T...>{{args...}}, {});
   return buf.count();
 }
 
 FMT_API void vprint(string_view fmt, format_args args);
 FMT_API void vprint(FILE* f, string_view fmt, format_args args);
-FMT_API void vprint_buffered(FILE* f, string_view fmt, format_args args);
 FMT_API void vprintln(FILE* f, string_view fmt, format_args args);
+FMT_API void vprint_buffered(FILE* f, string_view fmt, format_args args);
 
 /**
  * Formats `args` according to specifications in `fmt` and writes the output
@@ -3013,10 +2957,11 @@ FMT_API void vprintln(FILE* f, string_view fmt, format_args args);
  */
 template <typename... T>
 FMT_INLINE void print(format_string<T...> fmt, T&&... args) {
-  const auto& vargs = fmt::make_format_args(args...);
-  if (!detail::use_utf8()) return detail::vprint_mojibake(stdout, fmt, vargs);
-  return detail::is_locking<T...>() ? vprint_buffered(stdout, fmt, vargs)
-                                    : vprint(fmt, vargs);
+  vargs<T...> va = {{args...}};
+  if (detail::const_check(!detail::use_utf8))
+    return detail::vprint_mojibake(stdout, fmt.str, va, false);
+  return detail::is_locking<T...>() ? vprint_buffered(stdout, fmt.str, va)
+                                    : vprint(fmt.str, va);
 }
 
 /**
@@ -3029,19 +2974,21 @@ FMT_INLINE void print(format_string<T...> fmt, T&&... args) {
  */
 template <typename... T>
 FMT_INLINE void print(FILE* f, format_string<T...> fmt, T&&... args) {
-  const auto& vargs = fmt::make_format_args(args...);
-  if (!detail::use_utf8()) return detail::vprint_mojibake(f, fmt, vargs);
-  return detail::is_locking<T...>() ? vprint_buffered(f, fmt, vargs)
-                                    : vprint(f, fmt, vargs);
+  vargs<T...> va = {{args...}};
+  if (detail::const_check(!detail::use_utf8))
+    return detail::vprint_mojibake(f, fmt.str, va, false);
+  return detail::is_locking<T...>() ? vprint_buffered(f, fmt.str, va)
+                                    : vprint(f, fmt.str, va);
 }
 
 /// Formats `args` according to specifications in `fmt` and writes the output
 /// to the file `f` followed by a newline.
 template <typename... T>
 FMT_INLINE void println(FILE* f, format_string<T...> fmt, T&&... args) {
-  const auto& vargs = fmt::make_format_args(args...);
-  return detail::use_utf8() ? vprintln(f, fmt, vargs)
-                            : detail::vprint_mojibake(f, fmt, vargs, true);
+  vargs<T...> va = {{args...}};
+  return detail::const_check(detail::use_utf8)
+             ? vprintln(f, fmt.str, va)
+             : detail::vprint_mojibake(f, fmt.str, va, true);
 }
 
 /// Formats `args` according to specifications in `fmt` and writes the output
@@ -3051,8 +2998,10 @@ FMT_INLINE void println(format_string<T...> fmt, T&&... args) {
   return fmt::println(stdout, fmt, static_cast<T&&>(args)...);
 }
 
+FMT_PRAGMA_GCC(diagnostic pop)
+FMT_PRAGMA_CLANG(diagnostic pop)
+FMT_PRAGMA_GCC(pop_options)
 FMT_END_EXPORT
-FMT_GCC_PRAGMA("GCC pop_options")
 FMT_END_NAMESPACE
 
 #ifdef FMT_HEADER_ONLY
diff --git a/contrib/fmt/include/fmt/chrono.h b/contrib/fmt/include/fmt/chrono.h
index c93123fd33..9fbeeed679 100644
--- a/contrib/fmt/include/fmt/chrono.h
+++ b/contrib/fmt/include/fmt/chrono.h
@@ -24,38 +24,6 @@
 
 FMT_BEGIN_NAMESPACE
 
-// Check if std::chrono::local_t is available.
-#ifndef FMT_USE_LOCAL_TIME
-#  ifdef __cpp_lib_chrono
-#    define FMT_USE_LOCAL_TIME (__cpp_lib_chrono >= 201907L)
-#  else
-#    define FMT_USE_LOCAL_TIME 0
-#  endif
-#endif
-
-// Check if std::chrono::utc_timestamp is available.
-#ifndef FMT_USE_UTC_TIME
-#  ifdef __cpp_lib_chrono
-#    define FMT_USE_UTC_TIME (__cpp_lib_chrono >= 201907L)
-#  else
-#    define FMT_USE_UTC_TIME 0
-#  endif
-#endif
-
-// Enable tzset.
-#ifndef FMT_USE_TZSET
-// UWP doesn't provide _tzset.
-#  if FMT_HAS_INCLUDE("winapifamily.h")
-#    include <winapifamily.h>
-#  endif
-#  if defined(_WIN32) && (!defined(WINAPI_FAMILY) || \
-                          (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
-#    define FMT_USE_TZSET 1
-#  else
-#    define FMT_USE_TZSET 0
-#  endif
-#endif
-
 // Enable safe chrono durations, unless explicitly disabled.
 #ifndef FMT_SAFE_DURATION_CAST
 #  define FMT_SAFE_DURATION_CAST 1
@@ -70,6 +38,7 @@ FMT_BEGIN_NAMESPACE
 // Copyright Paul Dreik 2019
 namespace safe_duration_cast {
 
+// DEPRECATED!
 template <typename To, typename From,
           FMT_ENABLE_IF(!std::is_same<From, To>::value &&
                         std::numeric_limits<From>::is_signed ==
@@ -185,56 +154,6 @@ FMT_CONSTEXPR auto safe_float_conversion(const From from, int& ec) -> To {
   return from;
 }
 
-/// Safe duration cast between integral durations
-template <typename To, typename FromRep, typename FromPeriod,
-          FMT_ENABLE_IF(std::is_integral<FromRep>::value),
-          FMT_ENABLE_IF(std::is_integral<typename To::rep>::value)>
-auto safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
-                        int& ec) -> To {
-  using From = std::chrono::duration<FromRep, FromPeriod>;
-  ec = 0;
-  // the basic idea is that we need to convert from count() in the from type
-  // to count() in the To type, by multiplying it with this:
-  struct Factor
-      : std::ratio_divide<typename From::period, typename To::period> {};
-
-  static_assert(Factor::num > 0, "num must be positive");
-  static_assert(Factor::den > 0, "den must be positive");
-
-  // the conversion is like this: multiply from.count() with Factor::num
-  // /Factor::den and convert it to To::rep, all this without
-  // overflow/underflow. let's start by finding a suitable type that can hold
-  // both To, From and Factor::num
-  using IntermediateRep =
-      typename std::common_type<typename From::rep, typename To::rep,
-                                decltype(Factor::num)>::type;
-
-  // safe conversion to IntermediateRep
-  IntermediateRep count =
-      lossless_integral_conversion<IntermediateRep>(from.count(), ec);
-  if (ec) return {};
-  // multiply with Factor::num without overflow or underflow
-  if (detail::const_check(Factor::num != 1)) {
-    const auto max1 = detail::max_value<IntermediateRep>() / Factor::num;
-    if (count > max1) {
-      ec = 1;
-      return {};
-    }
-    const auto min1 =
-        (std::numeric_limits<IntermediateRep>::min)() / Factor::num;
-    if (detail::const_check(!std::is_unsigned<IntermediateRep>::value) &&
-        count < min1) {
-      ec = 1;
-      return {};
-    }
-    count *= Factor::num;
-  }
-
-  if (detail::const_check(Factor::den != 1)) count /= Factor::den;
-  auto tocount = lossless_integral_conversion<typename To::rep>(count, ec);
-  return ec ? To() : To(tocount);
-}
-
 /// Safe duration_cast between floating point durations
 template <typename To, typename FromRep, typename FromPeriod,
           FMT_ENABLE_IF(std::is_floating_point<FromRep>::value),
@@ -243,17 +162,6 @@ auto safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
                         int& ec) -> To {
   using From = std::chrono::duration<FromRep, FromPeriod>;
   ec = 0;
-  if (std::isnan(from.count())) {
-    // nan in, gives nan out. easy.
-    return To{std::numeric_limits<typename To::rep>::quiet_NaN()};
-  }
-  // maybe we should also check if from is denormal, and decide what to do about
-  // it.
-
-  // +-inf should be preserved.
-  if (std::isinf(from.count())) {
-    return To{from.count()};
-  }
 
   // the basic idea is that we need to convert from count() in the from type
   // to count() in the To type, by multiplying it with this:
@@ -314,25 +222,67 @@ auto safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
 }  // namespace safe_duration_cast
 #endif
 
+namespace detail {
+
+// Check if std::chrono::utc_time is available.
+#ifdef FMT_USE_UTC_TIME
+// Use the provided definition.
+#elif defined(__cpp_lib_chrono)
+#  define FMT_USE_UTC_TIME (__cpp_lib_chrono >= 201907L)
+#else
+#  define FMT_USE_UTC_TIME 0
+#endif
+#if FMT_USE_UTC_TIME
+using utc_clock = std::chrono::utc_clock;
+#else
+struct utc_clock {
+  template <typename T> void to_sys(T);
+};
+#endif
+
+// Check if std::chrono::local_time is available.
+#ifdef FMT_USE_LOCAL_TIME
+// Use the provided definition.
+#elif defined(__cpp_lib_chrono)
+#  define FMT_USE_LOCAL_TIME (__cpp_lib_chrono >= 201907L)
+#else
+#  define FMT_USE_LOCAL_TIME 0
+#endif
+#if FMT_USE_LOCAL_TIME
+using local_t = std::chrono::local_t;
+#else
+struct local_t {};
+#endif
+
+}  // namespace detail
+
+template <typename Duration>
+using sys_time = std::chrono::time_point<std::chrono::system_clock, Duration>;
+
+template <typename Duration>
+using utc_time = std::chrono::time_point<detail::utc_clock, Duration>;
+
+template <class Duration>
+using local_time = std::chrono::time_point<detail::local_t, Duration>;
+
+namespace detail {
+
 // Prevents expansion of a preceding token as a function-style macro.
 // Usage: f FMT_NOMACRO()
 #define FMT_NOMACRO
 
-namespace detail {
 template <typename T = void> struct null {};
-inline auto localtime_r FMT_NOMACRO(...) -> null<> { return null<>(); }
-inline auto localtime_s(...) -> null<> { return null<>(); }
 inline auto gmtime_r(...) -> null<> { return null<>(); }
 inline auto gmtime_s(...) -> null<> { return null<>(); }
 
 // It is defined here and not in ostream.h because the latter has expensive
 // includes.
-template <typename Streambuf> class formatbuf : public Streambuf {
+template <typename StreamBuf> class formatbuf : public StreamBuf {
  private:
-  using char_type = typename Streambuf::char_type;
-  using streamsize = decltype(std::declval<Streambuf>().sputn(nullptr, 0));
-  using int_type = typename Streambuf::int_type;
-  using traits_type = typename Streambuf::traits_type;
+  using char_type = typename StreamBuf::char_type;
+  using streamsize = decltype(std::declval<StreamBuf>().sputn(nullptr, 0));
+  using int_type = typename StreamBuf::int_type;
+  using traits_type = typename StreamBuf::traits_type;
 
   buffer<char_type>& buffer_;
 
@@ -364,26 +314,22 @@ inline auto get_classic_locale() -> const std::locale& {
 }
 
 template <typename CodeUnit> struct codecvt_result {
-  static constexpr const size_t max_size = 32;
+  static constexpr size_t max_size = 32;
   CodeUnit buf[max_size];
   CodeUnit* end;
 };
 
 template <typename CodeUnit>
-void write_codecvt(codecvt_result<CodeUnit>& out, string_view in_buf,
+void write_codecvt(codecvt_result<CodeUnit>& out, string_view in,
                    const std::locale& loc) {
-#if FMT_CLANG_VERSION
-#  pragma clang diagnostic push
-#  pragma clang diagnostic ignored "-Wdeprecated"
+  FMT_PRAGMA_CLANG(diagnostic push)
+  FMT_PRAGMA_CLANG(diagnostic ignored "-Wdeprecated")
   auto& f = std::use_facet<std::codecvt<CodeUnit, char, std::mbstate_t>>(loc);
-#  pragma clang diagnostic pop
-#else
-  auto& f = std::use_facet<std::codecvt<CodeUnit, char, std::mbstate_t>>(loc);
-#endif
+  FMT_PRAGMA_CLANG(diagnostic pop)
   auto mb = std::mbstate_t();
   const char* from_next = nullptr;
-  auto result = f.in(mb, in_buf.begin(), in_buf.end(), from_next,
-                     std::begin(out.buf), std::end(out.buf), out.end);
+  auto result = f.in(mb, in.begin(), in.end(), from_next, std::begin(out.buf),
+                     std::end(out.buf), out.end);
   if (result != std::codecvt_base::ok)
     FMT_THROW(format_error("failed to format time"));
 }
@@ -391,7 +337,7 @@ void write_codecvt(codecvt_result<CodeUnit>& out, string_view in_buf,
 template <typename OutputIt>
 auto write_encoded_tm_str(OutputIt out, string_view in, const std::locale& loc)
     -> OutputIt {
-  if (detail::use_utf8() && loc != get_classic_locale()) {
+  if (const_check(detail::use_utf8) && loc != get_classic_locale()) {
     // char16_t and char32_t codecvts are broken in MSVC (linkage errors) and
     // gcc-4.
 #if FMT_MSC_VERSION != 0 ||  \
@@ -462,25 +408,61 @@ auto write(OutputIt out, const std::tm& time, const std::locale& loc,
   return write_encoded_tm_str(out, string_view(buf.data(), buf.size()), loc);
 }
 
-template <typename Rep1, typename Rep2>
-struct is_same_arithmetic_type
-    : public std::integral_constant<bool,
-                                    (std::is_integral<Rep1>::value &&
-                                     std::is_integral<Rep2>::value) ||
-                                        (std::is_floating_point<Rep1>::value &&
-                                         std::is_floating_point<Rep2>::value)> {
-};
+template <typename T, typename U>
+using is_similar_arithmetic_type =
+    bool_constant<(std::is_integral<T>::value && std::is_integral<U>::value) ||
+                  (std::is_floating_point<T>::value &&
+                   std::is_floating_point<U>::value)>;
+
+FMT_NORETURN inline void throw_duration_error() {
+  FMT_THROW(format_error("cannot format duration"));
+}
 
-template <
-    typename To, typename FromRep, typename FromPeriod,
-    FMT_ENABLE_IF(is_same_arithmetic_type<FromRep, typename To::rep>::value)>
-auto fmt_duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
+// Cast one integral duration to another with an overflow check.
+template <typename To, typename FromRep, typename FromPeriod,
+          FMT_ENABLE_IF(std::is_integral<FromRep>::value&&
+                            std::is_integral<typename To::rep>::value)>
+auto duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
+#if !FMT_SAFE_DURATION_CAST
+  return std::chrono::duration_cast<To>(from);
+#else
+  // The conversion factor: to.count() == factor * from.count().
+  using factor = std::ratio_divide<FromPeriod, typename To::period>;
+
+  using common_rep = typename std::common_type<FromRep, typename To::rep,
+                                               decltype(factor::num)>::type;
+  common_rep count = from.count();  // This conversion is lossless.
+
+  // Multiply from.count() by factor and check for overflow.
+  if (const_check(factor::num != 1)) {
+    if (count > max_value<common_rep>() / factor::num) throw_duration_error();
+    const auto min = (std::numeric_limits<common_rep>::min)() / factor::num;
+    if (const_check(!std::is_unsigned<common_rep>::value) && count < min)
+      throw_duration_error();
+    count *= factor::num;
+  }
+  if (const_check(factor::den != 1)) count /= factor::den;
+  int ec = 0;
+  auto to =
+      To(safe_duration_cast::lossless_integral_conversion<typename To::rep>(
+          count, ec));
+  if (ec) throw_duration_error();
+  return to;
+#endif
+}
+
+template <typename To, typename FromRep, typename FromPeriod,
+          FMT_ENABLE_IF(std::is_floating_point<FromRep>::value&&
+                            std::is_floating_point<typename To::rep>::value)>
+auto duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
 #if FMT_SAFE_DURATION_CAST
+  // Preserve infinity and NaN.
+  if (!isfinite(from.count())) return static_cast<To>(from.count());
   // Throwing version of safe_duration_cast is only available for
   // integer to integer or float to float casts.
   int ec;
   To to = safe_duration_cast::safe_duration_cast<To>(from, ec);
-  if (ec) FMT_THROW(format_error("cannot format duration"));
+  if (ec) throw_duration_error();
   return to;
 #else
   // Standard duration cast, may overflow.
@@ -488,78 +470,28 @@ auto fmt_duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
 #endif
 }
 
-template <
-    typename To, typename FromRep, typename FromPeriod,
-    FMT_ENABLE_IF(!is_same_arithmetic_type<FromRep, typename To::rep>::value)>
-auto fmt_duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
-  // Mixed integer <-> float cast is not supported by safe_duration_cast.
+template <typename To, typename FromRep, typename FromPeriod,
+          FMT_ENABLE_IF(
+              !is_similar_arithmetic_type<FromRep, typename To::rep>::value)>
+auto duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
+  // Mixed integer <-> float cast is not supported by safe duration_cast.
   return std::chrono::duration_cast<To>(from);
 }
 
 template <typename Duration>
-auto to_time_t(
-    std::chrono::time_point<std::chrono::system_clock, Duration> time_point)
-    -> std::time_t {
+auto to_time_t(sys_time<Duration> time_point) -> std::time_t {
   // Cannot use std::chrono::system_clock::to_time_t since this would first
   // require a cast to std::chrono::system_clock::time_point, which could
   // overflow.
-  return fmt_duration_cast<std::chrono::duration<std::time_t>>(
+  return detail::duration_cast<std::chrono::duration<std::time_t>>(
              time_point.time_since_epoch())
       .count();
 }
+
 }  // namespace detail
 
 FMT_BEGIN_EXPORT
 
-/**
- * Converts given time since epoch as `std::time_t` value into calendar time,
- * expressed in local time. Unlike `std::localtime`, this function is
- * thread-safe on most platforms.
- */
-inline auto localtime(std::time_t time) -> std::tm {
-  struct dispatcher {
-    std::time_t time_;
-    std::tm tm_;
-
-    dispatcher(std::time_t t) : time_(t) {}
-
-    auto run() -> bool {
-      using namespace fmt::detail;
-      return handle(localtime_r(&time_, &tm_));
-    }
-
-    auto handle(std::tm* tm) -> bool { return tm != nullptr; }
-
-    auto handle(detail::null<>) -> bool {
-      using namespace fmt::detail;
-      return fallback(localtime_s(&tm_, &time_));
-    }
-
-    auto fallback(int res) -> bool { return res == 0; }
-
-#if !FMT_MSC_VERSION
-    auto fallback(detail::null<>) -> bool {
-      using namespace fmt::detail;
-      std::tm* tm = std::localtime(&time_);
-      if (tm) tm_ = *tm;
-      return tm != nullptr;
-    }
-#endif
-  };
-  dispatcher lt(time);
-  // Too big time values may be unsupported.
-  if (!lt.run()) FMT_THROW(format_error("time_t value out of range"));
-  return lt.tm_;
-}
-
-#if FMT_USE_LOCAL_TIME
-template <typename Duration>
-inline auto localtime(std::chrono::local_time<Duration> time) -> std::tm {
-  return localtime(
-      detail::to_time_t(std::chrono::current_zone()->to_sys(time)));
-}
-#endif
-
 /**
  * Converts given time since epoch as `std::time_t` value into calendar time,
  * expressed in Coordinated Universal Time (UTC). Unlike `std::gmtime`, this
@@ -570,24 +502,24 @@ inline auto gmtime(std::time_t time) -> std::tm {
     std::time_t time_;
     std::tm tm_;
 
-    dispatcher(std::time_t t) : time_(t) {}
+    inline dispatcher(std::time_t t) : time_(t) {}
 
-    auto run() -> bool {
+    inline auto run() -> bool {
       using namespace fmt::detail;
       return handle(gmtime_r(&time_, &tm_));
     }
 
-    auto handle(std::tm* tm) -> bool { return tm != nullptr; }
+    inline auto handle(std::tm* tm) -> bool { return tm != nullptr; }
 
-    auto handle(detail::null<>) -> bool {
+    inline auto handle(detail::null<>) -> bool {
       using namespace fmt::detail;
       return fallback(gmtime_s(&tm_, &time_));
     }
 
-    auto fallback(int res) -> bool { return res == 0; }
+    inline auto fallback(int res) -> bool { return res == 0; }
 
 #if !FMT_MSC_VERSION
-    auto fallback(detail::null<>) -> bool {
+    inline auto fallback(detail::null<>) -> bool {
       std::tm* tm = std::gmtime(&time_);
       if (tm) tm_ = *tm;
       return tm != nullptr;
@@ -601,9 +533,7 @@ inline auto gmtime(std::time_t time) -> std::tm {
 }
 
 template <typename Duration>
-inline auto gmtime(
-    std::chrono::time_point<std::chrono::system_clock, Duration> time_point)
-    -> std::tm {
+inline auto gmtime(sys_time<Duration> time_point) -> std::tm {
   return gmtime(detail::to_time_t(time_point));
 }
 
@@ -633,7 +563,7 @@ inline void write_digit2_separated(char* buf, unsigned a, unsigned b,
   // Add ASCII '0' to each digit byte and insert separators.
   digits |= 0x3030003030003030 | (usep << 16) | (usep << 40);
 
-  constexpr const size_t len = 8;
+  constexpr size_t len = 8;
   if (const_check(is_big_endian())) {
     char tmp[len];
     std::memcpy(tmp, &digits, len);
@@ -649,7 +579,8 @@ FMT_CONSTEXPR inline auto get_units() -> const char* {
   if (std::is_same<Period, std::femto>::value) return "fs";
   if (std::is_same<Period, std::pico>::value) return "ps";
   if (std::is_same<Period, std::nano>::value) return "ns";
-  if (std::is_same<Period, std::micro>::value) return "µs";
+  if (std::is_same<Period, std::micro>::value)
+    return detail::use_utf8 ? "µs" : "us";
   if (std::is_same<Period, std::milli>::value) return "ms";
   if (std::is_same<Period, std::centi>::value) return "cs";
   if (std::is_same<Period, std::deci>::value) return "ds";
@@ -728,9 +659,7 @@ FMT_CONSTEXPR auto parse_chrono_format(const Char* begin, const Char* end,
     if (ptr == end) FMT_THROW(format_error("invalid format"));
     c = *ptr++;
     switch (c) {
-    case '%':
-      handler.on_text(ptr - 1, ptr);
-      break;
+    case '%': handler.on_text(ptr - 1, ptr); break;
     case 'n': {
       const Char newline[] = {'\n'};
       handler.on_text(newline, newline + 1);
@@ -742,45 +671,21 @@ FMT_CONSTEXPR auto parse_chrono_format(const Char* begin, const Char* end,
       break;
     }
     // Year:
-    case 'Y':
-      handler.on_year(numeric_system::standard);
-      break;
-    case 'y':
-      handler.on_short_year(numeric_system::standard);
-      break;
-    case 'C':
-      handler.on_century(numeric_system::standard);
-      break;
-    case 'G':
-      handler.on_iso_week_based_year();
-      break;
-    case 'g':
-      handler.on_iso_week_based_short_year();
-      break;
+    case 'Y': handler.on_year(numeric_system::standard, pad); break;
+    case 'y': handler.on_short_year(numeric_system::standard); break;
+    case 'C': handler.on_century(numeric_system::standard); break;
+    case 'G': handler.on_iso_week_based_year(); break;
+    case 'g': handler.on_iso_week_based_short_year(); break;
     // Day of the week:
-    case 'a':
-      handler.on_abbr_weekday();
-      break;
-    case 'A':
-      handler.on_full_weekday();
-      break;
-    case 'w':
-      handler.on_dec0_weekday(numeric_system::standard);
-      break;
-    case 'u':
-      handler.on_dec1_weekday(numeric_system::standard);
-      break;
+    case 'a': handler.on_abbr_weekday(); break;
+    case 'A': handler.on_full_weekday(); break;
+    case 'w': handler.on_dec0_weekday(numeric_system::standard); break;
+    case 'u': handler.on_dec1_weekday(numeric_system::standard); break;
     // Month:
     case 'b':
-    case 'h':
-      handler.on_abbr_month();
-      break;
-    case 'B':
-      handler.on_full_month();
-      break;
-    case 'm':
-      handler.on_dec_month(numeric_system::standard);
-      break;
+    case 'h': handler.on_abbr_month(); break;
+    case 'B': handler.on_full_month(); break;
+    case 'm': handler.on_dec_month(numeric_system::standard, pad); break;
     // Day of the year/month:
     case 'U':
       handler.on_dec0_week_of_year(numeric_system::standard, pad);
@@ -788,99 +693,44 @@ FMT_CONSTEXPR auto parse_chrono_format(const Char* begin, const Char* end,
     case 'W':
       handler.on_dec1_week_of_year(numeric_system::standard, pad);
       break;
-    case 'V':
-      handler.on_iso_week_of_year(numeric_system::standard, pad);
-      break;
-    case 'j':
-      handler.on_day_of_year();
-      break;
-    case 'd':
-      handler.on_day_of_month(numeric_system::standard, pad);
-      break;
+    case 'V': handler.on_iso_week_of_year(numeric_system::standard, pad); break;
+    case 'j': handler.on_day_of_year(pad); break;
+    case 'd': handler.on_day_of_month(numeric_system::standard, pad); break;
     case 'e':
       handler.on_day_of_month(numeric_system::standard, pad_type::space);
       break;
     // Hour, minute, second:
-    case 'H':
-      handler.on_24_hour(numeric_system::standard, pad);
-      break;
-    case 'I':
-      handler.on_12_hour(numeric_system::standard, pad);
-      break;
-    case 'M':
-      handler.on_minute(numeric_system::standard, pad);
-      break;
-    case 'S':
-      handler.on_second(numeric_system::standard, pad);
-      break;
+    case 'H': handler.on_24_hour(numeric_system::standard, pad); break;
+    case 'I': handler.on_12_hour(numeric_system::standard, pad); break;
+    case 'M': handler.on_minute(numeric_system::standard, pad); break;
+    case 'S': handler.on_second(numeric_system::standard, pad); break;
     // Other:
-    case 'c':
-      handler.on_datetime(numeric_system::standard);
-      break;
-    case 'x':
-      handler.on_loc_date(numeric_system::standard);
-      break;
-    case 'X':
-      handler.on_loc_time(numeric_system::standard);
-      break;
-    case 'D':
-      handler.on_us_date();
-      break;
-    case 'F':
-      handler.on_iso_date();
-      break;
-    case 'r':
-      handler.on_12_hour_time();
-      break;
-    case 'R':
-      handler.on_24_hour_time();
-      break;
-    case 'T':
-      handler.on_iso_time();
-      break;
-    case 'p':
-      handler.on_am_pm();
-      break;
-    case 'Q':
-      handler.on_duration_value();
-      break;
-    case 'q':
-      handler.on_duration_unit();
-      break;
-    case 'z':
-      handler.on_utc_offset(numeric_system::standard);
-      break;
-    case 'Z':
-      handler.on_tz_name();
-      break;
+    case 'c': handler.on_datetime(numeric_system::standard); break;
+    case 'x': handler.on_loc_date(numeric_system::standard); break;
+    case 'X': handler.on_loc_time(numeric_system::standard); break;
+    case 'D': handler.on_us_date(); break;
+    case 'F': handler.on_iso_date(); break;
+    case 'r': handler.on_12_hour_time(); break;
+    case 'R': handler.on_24_hour_time(); break;
+    case 'T': handler.on_iso_time(); break;
+    case 'p': handler.on_am_pm(); break;
+    case 'Q': handler.on_duration_value(); break;
+    case 'q': handler.on_duration_unit(); break;
+    case 'z': handler.on_utc_offset(numeric_system::standard); break;
+    case 'Z': handler.on_tz_name(); break;
     // Alternative representation:
     case 'E': {
       if (ptr == end) FMT_THROW(format_error("invalid format"));
       c = *ptr++;
       switch (c) {
-      case 'Y':
-        handler.on_year(numeric_system::alternative);
-        break;
-      case 'y':
-        handler.on_offset_year();
-        break;
-      case 'C':
-        handler.on_century(numeric_system::alternative);
-        break;
-      case 'c':
-        handler.on_datetime(numeric_system::alternative);
-        break;
-      case 'x':
-        handler.on_loc_date(numeric_system::alternative);
-        break;
-      case 'X':
-        handler.on_loc_time(numeric_system::alternative);
-        break;
-      case 'z':
-        handler.on_utc_offset(numeric_system::alternative);
-        break;
-      default:
-        FMT_THROW(format_error("invalid format"));
+      case 'Y': handler.on_year(numeric_system::alternative, pad); break;
+      case 'y': handler.on_offset_year(); break;
+      case 'C': handler.on_century(numeric_system::alternative); break;
+      case 'c': handler.on_datetime(numeric_system::alternative); break;
+      case 'x': handler.on_loc_date(numeric_system::alternative); break;
+      case 'X': handler.on_loc_time(numeric_system::alternative); break;
+      case 'z': handler.on_utc_offset(numeric_system::alternative); break;
+      default:  FMT_THROW(format_error("invalid format"));
       }
       break;
     }
@@ -888,12 +738,8 @@ FMT_CONSTEXPR auto parse_chrono_format(const Char* begin, const Char* end,
       if (ptr == end) FMT_THROW(format_error("invalid format"));
       c = *ptr++;
       switch (c) {
-      case 'y':
-        handler.on_short_year(numeric_system::alternative);
-        break;
-      case 'm':
-        handler.on_dec_month(numeric_system::alternative);
-        break;
+      case 'y': handler.on_short_year(numeric_system::alternative); break;
+      case 'm': handler.on_dec_month(numeric_system::alternative, pad); break;
       case 'U':
         handler.on_dec0_week_of_year(numeric_system::alternative, pad);
         break;
@@ -909,33 +755,17 @@ FMT_CONSTEXPR auto parse_chrono_format(const Char* begin, const Char* end,
       case 'e':
         handler.on_day_of_month(numeric_system::alternative, pad_type::space);
         break;
-      case 'w':
-        handler.on_dec0_weekday(numeric_system::alternative);
-        break;
-      case 'u':
-        handler.on_dec1_weekday(numeric_system::alternative);
-        break;
-      case 'H':
-        handler.on_24_hour(numeric_system::alternative, pad);
-        break;
-      case 'I':
-        handler.on_12_hour(numeric_system::alternative, pad);
-        break;
-      case 'M':
-        handler.on_minute(numeric_system::alternative, pad);
-        break;
-      case 'S':
-        handler.on_second(numeric_system::alternative, pad);
-        break;
-      case 'z':
-        handler.on_utc_offset(numeric_system::alternative);
-        break;
-      default:
-        FMT_THROW(format_error("invalid format"));
+      case 'w': handler.on_dec0_weekday(numeric_system::alternative); break;
+      case 'u': handler.on_dec1_weekday(numeric_system::alternative); break;
+      case 'H': handler.on_24_hour(numeric_system::alternative, pad); break;
+      case 'I': handler.on_12_hour(numeric_system::alternative, pad); break;
+      case 'M': handler.on_minute(numeric_system::alternative, pad); break;
+      case 'S': handler.on_second(numeric_system::alternative, pad); break;
+      case 'z': handler.on_utc_offset(numeric_system::alternative); break;
+      default:  FMT_THROW(format_error("invalid format"));
       }
       break;
-    default:
-      FMT_THROW(format_error("invalid format"));
+    default: FMT_THROW(format_error("invalid format"));
     }
     begin = ptr;
   }
@@ -947,7 +777,7 @@ template <typename Derived> struct null_chrono_spec_handler {
   FMT_CONSTEXPR void unsupported() {
     static_cast<Derived*>(this)->unsupported();
   }
-  FMT_CONSTEXPR void on_year(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_year(numeric_system, pad_type) { unsupported(); }
   FMT_CONSTEXPR void on_short_year(numeric_system) { unsupported(); }
   FMT_CONSTEXPR void on_offset_year() { unsupported(); }
   FMT_CONSTEXPR void on_century(numeric_system) { unsupported(); }
@@ -959,7 +789,7 @@ template <typename Derived> struct null_chrono_spec_handler {
   FMT_CONSTEXPR void on_dec1_weekday(numeric_system) { unsupported(); }
   FMT_CONSTEXPR void on_abbr_month() { unsupported(); }
   FMT_CONSTEXPR void on_full_month() { unsupported(); }
-  FMT_CONSTEXPR void on_dec_month(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_dec_month(numeric_system, pad_type) { unsupported(); }
   FMT_CONSTEXPR void on_dec0_week_of_year(numeric_system, pad_type) {
     unsupported();
   }
@@ -969,7 +799,7 @@ template <typename Derived> struct null_chrono_spec_handler {
   FMT_CONSTEXPR void on_iso_week_of_year(numeric_system, pad_type) {
     unsupported();
   }
-  FMT_CONSTEXPR void on_day_of_year() { unsupported(); }
+  FMT_CONSTEXPR void on_day_of_year(pad_type) { unsupported(); }
   FMT_CONSTEXPR void on_day_of_month(numeric_system, pad_type) {
     unsupported();
   }
@@ -992,12 +822,21 @@ template <typename Derived> struct null_chrono_spec_handler {
   FMT_CONSTEXPR void on_tz_name() { unsupported(); }
 };
 
-struct tm_format_checker : null_chrono_spec_handler<tm_format_checker> {
-  FMT_NORETURN void unsupported() { FMT_THROW(format_error("no format")); }
+class tm_format_checker : public null_chrono_spec_handler<tm_format_checker> {
+ private:
+  bool has_timezone_ = false;
+
+ public:
+  constexpr explicit tm_format_checker(bool has_timezone)
+      : has_timezone_(has_timezone) {}
+
+  FMT_NORETURN inline void unsupported() {
+    FMT_THROW(format_error("no format"));
+  }
 
   template <typename Char>
   FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
-  FMT_CONSTEXPR void on_year(numeric_system) {}
+  FMT_CONSTEXPR void on_year(numeric_system, pad_type) {}
   FMT_CONSTEXPR void on_short_year(numeric_system) {}
   FMT_CONSTEXPR void on_offset_year() {}
   FMT_CONSTEXPR void on_century(numeric_system) {}
@@ -1009,11 +848,11 @@ struct tm_format_checker : null_chrono_spec_handler<tm_format_checker> {
   FMT_CONSTEXPR void on_dec1_weekday(numeric_system) {}
   FMT_CONSTEXPR void on_abbr_month() {}
   FMT_CONSTEXPR void on_full_month() {}
-  FMT_CONSTEXPR void on_dec_month(numeric_system) {}
+  FMT_CONSTEXPR void on_dec_month(numeric_system, pad_type) {}
   FMT_CONSTEXPR void on_dec0_week_of_year(numeric_system, pad_type) {}
   FMT_CONSTEXPR void on_dec1_week_of_year(numeric_system, pad_type) {}
   FMT_CONSTEXPR void on_iso_week_of_year(numeric_system, pad_type) {}
-  FMT_CONSTEXPR void on_day_of_year() {}
+  FMT_CONSTEXPR void on_day_of_year(pad_type) {}
   FMT_CONSTEXPR void on_day_of_month(numeric_system, pad_type) {}
   FMT_CONSTEXPR void on_24_hour(numeric_system, pad_type) {}
   FMT_CONSTEXPR void on_12_hour(numeric_system, pad_type) {}
@@ -1028,8 +867,12 @@ struct tm_format_checker : null_chrono_spec_handler<tm_format_checker> {
   FMT_CONSTEXPR void on_24_hour_time() {}
   FMT_CONSTEXPR void on_iso_time() {}
   FMT_CONSTEXPR void on_am_pm() {}
-  FMT_CONSTEXPR void on_utc_offset(numeric_system) {}
-  FMT_CONSTEXPR void on_tz_name() {}
+  FMT_CONSTEXPR void on_utc_offset(numeric_system) {
+    if (!has_timezone_) FMT_THROW(format_error("no timezone"));
+  }
+  FMT_CONSTEXPR void on_tz_name() {
+    if (!has_timezone_) FMT_THROW(format_error("no timezone"));
+  }
 };
 
 inline auto tm_wday_full_name(int wday) -> const char* {
@@ -1059,33 +902,35 @@ inline auto tm_mon_short_name(int mon) -> const char* {
 }
 
 template <typename T, typename = void>
-struct has_member_data_tm_gmtoff : std::false_type {};
+struct has_tm_gmtoff : std::false_type {};
 template <typename T>
-struct has_member_data_tm_gmtoff<T, void_t<decltype(T::tm_gmtoff)>>
-    : std::true_type {};
+struct has_tm_gmtoff<T, void_t<decltype(T::tm_gmtoff)>> : std::true_type {};
 
-template <typename T, typename = void>
-struct has_member_data_tm_zone : std::false_type {};
+template <typename T, typename = void> struct has_tm_zone : std::false_type {};
 template <typename T>
-struct has_member_data_tm_zone<T, void_t<decltype(T::tm_zone)>>
-    : std::true_type {};
+struct has_tm_zone<T, void_t<decltype(T::tm_zone)>> : std::true_type {};
 
-#if FMT_USE_TZSET
-inline void tzset_once() {
-  static bool init = []() -> bool {
-    _tzset();
-    return true;
-  }();
-  ignore_unused(init);
+template <typename T, FMT_ENABLE_IF(has_tm_zone<T>::value)>
+auto set_tm_zone(T& time, char* tz) -> bool {
+  time.tm_zone = tz;
+  return true;
+}
+template <typename T, FMT_ENABLE_IF(!has_tm_zone<T>::value)>
+auto set_tm_zone(T&, char*) -> bool {
+  return false;
+}
+
+inline auto utc() -> char* {
+  static char tz[] = "UTC";
+  return tz;
 }
-#endif
 
 // Converts value to Int and checks that it's in the range [0, upper).
 template <typename T, typename Int, FMT_ENABLE_IF(std::is_integral<T>::value)>
 inline auto to_nonnegative_int(T value, Int upper) -> Int {
   if (!std::is_unsigned<Int>::value &&
       (value < 0 || to_unsigned(value) > to_unsigned(upper))) {
-    FMT_THROW(fmt::format_error("chrono value is out of range"));
+    FMT_THROW(format_error("chrono value is out of range"));
   }
   return static_cast<Int>(value);
 }
@@ -1129,16 +974,16 @@ void write_fractional_seconds(OutputIt& out, Duration d, int precision = -1) {
   using subsecond_precision = std::chrono::duration<
       typename std::common_type<typename Duration::rep,
                                 std::chrono::seconds::rep>::type,
-      std::ratio<1, detail::pow10(num_fractional_digits)>>;
+      std::ratio<1, pow10(num_fractional_digits)>>;
 
-  const auto fractional = d - fmt_duration_cast<std::chrono::seconds>(d);
+  const auto fractional = d - detail::duration_cast<std::chrono::seconds>(d);
   const auto subseconds =
       std::chrono::treat_as_floating_point<
           typename subsecond_precision::rep>::value
           ? fractional.count()
-          : fmt_duration_cast<subsecond_precision>(fractional).count();
+          : detail::duration_cast<subsecond_precision>(fractional).count();
   auto n = static_cast<uint32_or_64_or_128_t<long long>>(subseconds);
-  const int num_digits = detail::count_digits(n);
+  const int num_digits = count_digits(n);
 
   int leading_zeroes = (std::max)(0, num_fractional_digits - num_digits);
   if (precision < 0) {
@@ -1147,23 +992,21 @@ void write_fractional_seconds(OutputIt& out, Duration d, int precision = -1) {
                         std::chrono::seconds::period>::value) {
       *out++ = '.';
       out = detail::fill_n(out, leading_zeroes, '0');
-      out = format_decimal<Char>(out, n, num_digits).end;
+      out = format_decimal<Char>(out, n, num_digits);
     }
   } else if (precision > 0) {
     *out++ = '.';
-    leading_zeroes = (std::min)(leading_zeroes, precision);
+    leading_zeroes = min_of(leading_zeroes, precision);
     int remaining = precision - leading_zeroes;
     out = detail::fill_n(out, leading_zeroes, '0');
     if (remaining < num_digits) {
       int num_truncated_digits = num_digits - remaining;
-      n /= to_unsigned(detail::pow10(to_unsigned(num_truncated_digits)));
-      if (n) {
-        out = format_decimal<Char>(out, n, remaining).end;
-      }
+      n /= to_unsigned(pow10(to_unsigned(num_truncated_digits)));
+      if (n != 0) out = format_decimal<Char>(out, n, remaining);
       return;
     }
-    if (n) {
-      out = format_decimal<Char>(out, n, num_digits).end;
+    if (n != 0) {
+      out = format_decimal<Char>(out, n, num_digits);
       remaining -= num_digits;
     }
     out = detail::fill_n(out, remaining, '0');
@@ -1172,7 +1015,7 @@ void write_fractional_seconds(OutputIt& out, Duration d, int precision = -1) {
 
 // Format subseconds which are given as a floating point type with an
 // appropriate number of digits. We cannot pass the Duration here, as we
-// explicitly need to pass the Rep value in the chrono_formatter.
+// explicitly need to pass the Rep value in the duration_formatter.
 template <typename Duration>
 void write_floating_seconds(memory_buffer& buf, Duration duration,
                             int num_fractional_digits = -1) {
@@ -1206,7 +1049,7 @@ class tm_writer {
   static constexpr int days_per_week = 7;
 
   const std::locale& loc_;
-  const bool is_classic_;
+  bool is_classic_;
   OutputIt out_;
   const Duration* subsecs_;
   const std::tm& tm_;
@@ -1242,8 +1085,8 @@ class tm_writer {
   }
 
   auto tm_hour12() const noexcept -> int {
-    const auto h = tm_hour();
-    const auto z = h < 12 ? h : h - 12;
+    auto h = tm_hour();
+    auto z = h < 12 ? h : h - 12;
     return z == 0 ? 12 : z;
   }
 
@@ -1259,11 +1102,11 @@ class tm_writer {
 
   // Algorithm: https://en.wikipedia.org/wiki/ISO_week_date.
   auto iso_year_weeks(long long curr_year) const noexcept -> int {
-    const auto prev_year = curr_year - 1;
-    const auto curr_p =
+    auto prev_year = curr_year - 1;
+    auto curr_p =
         (curr_year + curr_year / 4 - curr_year / 100 + curr_year / 400) %
         days_per_week;
-    const auto prev_p =
+    auto prev_p =
         (prev_year + prev_year / 4 - prev_year / 100 + prev_year / 400) %
         days_per_week;
     return 52 + ((curr_p == 4 || prev_p == 3) ? 1 : 0);
@@ -1273,15 +1116,15 @@ class tm_writer {
            days_per_week;
   }
   auto tm_iso_week_year() const noexcept -> long long {
-    const auto year = tm_year();
-    const auto w = iso_week_num(tm_yday(), tm_wday());
+    auto year = tm_year();
+    auto w = iso_week_num(tm_yday(), tm_wday());
     if (w < 1) return year - 1;
     if (w > iso_year_weeks(year)) return year + 1;
     return year;
   }
   auto tm_iso_week_of_year() const noexcept -> int {
-    const auto year = tm_year();
-    const auto w = iso_week_num(tm_yday(), tm_wday());
+    auto year = tm_year();
+    auto w = iso_week_num(tm_yday(), tm_wday());
     if (w < 1) return iso_year_weeks(year - 1);
     if (w > iso_year_weeks(year)) return 1;
     return w;
@@ -1307,30 +1150,27 @@ class tm_writer {
     }
   }
 
-  void write_year_extended(long long year) {
+  void write_year_extended(long long year, pad_type pad) {
     // At least 4 characters.
     int width = 4;
-    if (year < 0) {
-      *out_++ = '-';
+    bool negative = year < 0;
+    if (negative) {
       year = 0 - year;
       --width;
     }
     uint32_or_64_or_128_t<long long> n = to_unsigned(year);
     const int num_digits = count_digits(n);
+    if (negative && pad == pad_type::zero) *out_++ = '-';
     if (width > num_digits)
-      out_ = detail::fill_n(out_, width - num_digits, '0');
-    out_ = format_decimal<Char>(out_, n, num_digits).end;
+      out_ = detail::write_padding(out_, pad, width - num_digits);
+    if (negative && pad != pad_type::zero) *out_++ = '-';
+    out_ = format_decimal<Char>(out_, n, num_digits);
   }
-  void write_year(long long year) {
-    if (year >= 0 && year < 10000) {
-      write2(static_cast<int>(year / 100));
-      write2(static_cast<int>(year % 100));
-    } else {
-      write_year_extended(year);
-    }
+  void write_year(long long year, pad_type pad) {
+    write_year_extended(year, pad);
   }
 
-  void write_utc_offset(long offset, numeric_system ns) {
+  void write_utc_offset(long long offset, numeric_system ns) {
     if (offset < 0) {
       *out_++ = '-';
       offset = -offset;
@@ -1342,47 +1182,23 @@ class tm_writer {
     if (ns != numeric_system::standard) *out_++ = ':';
     write2(static_cast<int>(offset % 60));
   }
-  template <typename T, FMT_ENABLE_IF(has_member_data_tm_gmtoff<T>::value)>
-  void format_utc_offset_impl(const T& tm, numeric_system ns) {
+
+  template <typename T, FMT_ENABLE_IF(has_tm_gmtoff<T>::value)>
+  void format_utc_offset(const T& tm, numeric_system ns) {
     write_utc_offset(tm.tm_gmtoff, ns);
   }
-  template <typename T, FMT_ENABLE_IF(!has_member_data_tm_gmtoff<T>::value)>
-  void format_utc_offset_impl(const T& tm, numeric_system ns) {
-#if defined(_WIN32) && defined(_UCRT)
-#  if FMT_USE_TZSET
-    tzset_once();
-#  endif
-    long offset = 0;
-    _get_timezone(&offset);
-    if (tm.tm_isdst) {
-      long dstbias = 0;
-      _get_dstbias(&dstbias);
-      offset += dstbias;
-    }
-    write_utc_offset(-offset, ns);
-#else
-    if (ns == numeric_system::standard) return format_localized('z');
-
-    // Extract timezone offset from timezone conversion functions.
-    std::tm gtm = tm;
-    std::time_t gt = std::mktime(&gtm);
-    std::tm ltm = gmtime(gt);
-    std::time_t lt = std::mktime(&ltm);
-    long offset = gt - lt;
-    write_utc_offset(offset, ns);
-#endif
+  template <typename T, FMT_ENABLE_IF(!has_tm_gmtoff<T>::value)>
+  void format_utc_offset(const T&, numeric_system ns) {
+    write_utc_offset(0, ns);
   }
 
-  template <typename T, FMT_ENABLE_IF(has_member_data_tm_zone<T>::value)>
-  void format_tz_name_impl(const T& tm) {
-    if (is_classic_)
-      out_ = write_tm_str<Char>(out_, tm.tm_zone, loc_);
-    else
-      format_localized('Z');
+  template <typename T, FMT_ENABLE_IF(has_tm_zone<T>::value)>
+  void format_tz_name(const T& tm) {
+    out_ = write_tm_str<Char>(out_, tm.tm_zone, loc_);
   }
-  template <typename T, FMT_ENABLE_IF(!has_member_data_tm_zone<T>::value)>
-  void format_tz_name_impl(const T&) {
-    format_localized('Z');
+  template <typename T, FMT_ENABLE_IF(!has_tm_zone<T>::value)>
+  void format_tz_name(const T&) {
+    out_ = std::copy_n(utc(), 3, out_);
   }
 
   void format_localized(char format, char modifier = 0) {
@@ -1452,7 +1268,7 @@ class tm_writer {
       *out_++ = ' ';
       on_iso_time();
       *out_++ = ' ';
-      on_year(numeric_system::standard);
+      on_year(numeric_system::standard, pad_type::space);
     } else {
       format_localized('c', ns == numeric_system::standard ? '\0' : 'E');
     }
@@ -1481,10 +1297,10 @@ class tm_writer {
     char buf[10];
     size_t offset = 0;
     if (year >= 0 && year < 10000) {
-      copy2(buf, digits2(static_cast<size_t>(year / 100)));
+      write2digits(buf, static_cast<size_t>(year / 100));
     } else {
       offset = 4;
-      write_year_extended(year);
+      write_year_extended(year, pad_type::zero);
       year = 0;
     }
     write_digit2_separated(buf + 2, static_cast<unsigned>(year % 100),
@@ -1493,12 +1309,12 @@ class tm_writer {
     out_ = copy<Char>(std::begin(buf) + offset, std::end(buf), out_);
   }
 
-  void on_utc_offset(numeric_system ns) { format_utc_offset_impl(tm_, ns); }
-  void on_tz_name() { format_tz_name_impl(tm_); }
+  void on_utc_offset(numeric_system ns) { format_utc_offset(tm_, ns); }
+  void on_tz_name() { format_tz_name(tm_); }
 
-  void on_year(numeric_system ns) {
+  void on_year(numeric_system ns, pad_type pad) {
     if (is_classic_ || ns == numeric_system::standard)
-      return write_year(tm_year());
+      return write_year(tm_year(), pad);
     format_localized('Y', 'E');
   }
   void on_short_year(numeric_system ns) {
@@ -1529,9 +1345,9 @@ class tm_writer {
     }
   }
 
-  void on_dec_month(numeric_system ns) {
+  void on_dec_month(numeric_system ns, pad_type pad) {
     if (is_classic_ || ns == numeric_system::standard)
-      return write2(tm_mon() + 1);
+      return write2(tm_mon() + 1, pad);
     format_localized('m', 'O');
   }
 
@@ -1558,16 +1374,23 @@ class tm_writer {
     format_localized('V', 'O');
   }
 
-  void on_iso_week_based_year() { write_year(tm_iso_week_year()); }
+  void on_iso_week_based_year() {
+    write_year(tm_iso_week_year(), pad_type::zero);
+  }
   void on_iso_week_based_short_year() {
     write2(split_year_lower(tm_iso_week_year()));
   }
 
-  void on_day_of_year() {
+  void on_day_of_year(pad_type pad) {
     auto yday = tm_yday() + 1;
-    write1(yday / 100);
-    write2(yday % 100);
+    auto digit1 = yday / 100;
+    if (digit1 != 0)
+      write1(digit1);
+    else
+      out_ = detail::write_padding(out_, pad);
+    write2(yday % 100, pad);
   }
+
   void on_day_of_month(numeric_system ns, pad_type pad) {
     if (is_classic_ || ns == numeric_system::standard)
       return write2(tm_mday(), pad);
@@ -1599,7 +1422,7 @@ class tm_writer {
           write_floating_seconds(buf, *subsecs_);
           if (buf.size() > 1) {
             // Remove the leading "0", write something like ".123".
-            out_ = std::copy(buf.begin() + 1, buf.end(), out_);
+            out_ = copy<Char>(buf.begin() + 1, buf.end(), out_);
           }
         } else {
           write_fractional_seconds<Char>(out_, *subsecs_);
@@ -1651,11 +1474,11 @@ class tm_writer {
 struct chrono_format_checker : null_chrono_spec_handler<chrono_format_checker> {
   bool has_precision_integral = false;
 
-  FMT_NORETURN void unsupported() { FMT_THROW(format_error("no date")); }
+  FMT_NORETURN inline void unsupported() { FMT_THROW(format_error("no date")); }
 
   template <typename Char>
   FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
-  FMT_CONSTEXPR void on_day_of_year() {}
+  FMT_CONSTEXPR void on_day_of_year(pad_type) {}
   FMT_CONSTEXPR void on_24_hour(numeric_system, pad_type) {}
   FMT_CONSTEXPR void on_12_hour(numeric_system, pad_type) {}
   FMT_CONSTEXPR void on_minute(numeric_system, pad_type) {}
@@ -1665,9 +1488,8 @@ struct chrono_format_checker : null_chrono_spec_handler<chrono_format_checker> {
   FMT_CONSTEXPR void on_iso_time() {}
   FMT_CONSTEXPR void on_am_pm() {}
   FMT_CONSTEXPR void on_duration_value() const {
-    if (has_precision_integral) {
+    if (has_precision_integral)
       FMT_THROW(format_error("precision not allowed for this argument type"));
-    }
   }
   FMT_CONSTEXPR void on_duration_unit() {}
 };
@@ -1702,22 +1524,20 @@ template <typename Rep, typename Period,
           FMT_ENABLE_IF(std::is_integral<Rep>::value)>
 inline auto get_milliseconds(std::chrono::duration<Rep, Period> d)
     -> std::chrono::duration<Rep, std::milli> {
-  // this may overflow and/or the result may not fit in the
-  // target type.
+  // This may overflow and/or the result may not fit in the target type.
 #if FMT_SAFE_DURATION_CAST
-  using CommonSecondsType =
+  using common_seconds_type =
       typename std::common_type<decltype(d), std::chrono::seconds>::type;
-  const auto d_as_common = fmt_duration_cast<CommonSecondsType>(d);
-  const auto d_as_whole_seconds =
-      fmt_duration_cast<std::chrono::seconds>(d_as_common);
-  // this conversion should be nonproblematic
-  const auto diff = d_as_common - d_as_whole_seconds;
-  const auto ms =
-      fmt_duration_cast<std::chrono::duration<Rep, std::milli>>(diff);
+  auto d_as_common = detail::duration_cast<common_seconds_type>(d);
+  auto d_as_whole_seconds =
+      detail::duration_cast<std::chrono::seconds>(d_as_common);
+  // This conversion should be nonproblematic.
+  auto diff = d_as_common - d_as_whole_seconds;
+  auto ms = detail::duration_cast<std::chrono::duration<Rep, std::milli>>(diff);
   return ms;
 #else
-  auto s = fmt_duration_cast<std::chrono::seconds>(d);
-  return fmt_duration_cast<std::chrono::milliseconds>(d - s);
+  auto s = detail::duration_cast<std::chrono::seconds>(d);
+  return detail::duration_cast<std::chrono::milliseconds>(d - s);
 #endif
 }
 
@@ -1732,14 +1552,14 @@ template <typename Char, typename Rep, typename OutputIt,
 auto format_duration_value(OutputIt out, Rep val, int precision) -> OutputIt {
   auto specs = format_specs();
   specs.precision = precision;
-  specs.type =
-      precision >= 0 ? presentation_type::fixed : presentation_type::general;
+  specs.set_type(precision >= 0 ? presentation_type::fixed
+                                : presentation_type::general);
   return write<Char>(out, val, specs);
 }
 
 template <typename Char, typename OutputIt>
 auto copy_unit(string_view unit, OutputIt out, Char) -> OutputIt {
-  return std::copy(unit.begin(), unit.end(), out);
+  return copy<Char>(unit.begin(), unit.end(), out);
 }
 
 template <typename OutputIt>
@@ -1747,7 +1567,7 @@ auto copy_unit(string_view unit, OutputIt out, wchar_t) -> OutputIt {
   // This works when wchar_t is UTF-32 because units only contain characters
   // that have the same representation in UTF-16 and UTF-32.
   utf8_to_utf16 u(unit);
-  return std::copy(u.c_str(), u.c_str() + u.size(), out);
+  return copy<wchar_t>(u.c_str(), u.c_str() + u.size(), out);
 }
 
 template <typename Char, typename Period, typename OutputIt>
@@ -1773,46 +1593,45 @@ class get_locale {
   bool has_locale_ = false;
 
  public:
-  get_locale(bool localized, locale_ref loc) : has_locale_(localized) {
-#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
-    if (localized)
-      ::new (&locale_) std::locale(loc.template get<std::locale>());
+  inline get_locale(bool localized, locale_ref loc) : has_locale_(localized) {
+    if (!localized) return;
+    ignore_unused(loc);
+    ::new (&locale_) std::locale(
+#if FMT_USE_LOCALE
+        loc.template get<std::locale>()
 #endif
+    );
   }
-  ~get_locale() {
+  inline ~get_locale() {
     if (has_locale_) locale_.~locale();
   }
-  operator const std::locale&() const {
+  inline operator const std::locale&() const {
     return has_locale_ ? locale_ : get_classic_locale();
   }
 };
 
-template <typename FormatContext, typename OutputIt, typename Rep,
-          typename Period>
-struct chrono_formatter {
-  FormatContext& context;
-  OutputIt out;
-  int precision;
-  bool localized = false;
+template <typename Char, typename Rep, typename Period>
+struct duration_formatter {
+  using iterator = basic_appender<Char>;
+  iterator out;
   // rep is unsigned to avoid overflow.
   using rep =
       conditional_t<std::is_integral<Rep>::value && sizeof(Rep) < sizeof(int),
                     unsigned, typename make_unsigned_or_unchanged<Rep>::type>;
   rep val;
+  int precision;
+  locale_ref locale;
+  bool localized = false;
   using seconds = std::chrono::duration<rep>;
   seconds s;
   using milliseconds = std::chrono::duration<rep, std::milli>;
   bool negative;
 
-  using char_type = typename FormatContext::char_type;
-  using tm_writer_type = tm_writer<OutputIt, char_type>;
+  using tm_writer_type = tm_writer<iterator, Char>;
 
-  chrono_formatter(FormatContext& ctx, OutputIt o,
-                   std::chrono::duration<Rep, Period> d)
-      : context(ctx),
-        out(o),
-        val(static_cast<rep>(d.count())),
-        negative(false) {
+  duration_formatter(iterator o, std::chrono::duration<Rep, Period> d,
+                     locale_ref loc)
+      : out(o), val(static_cast<rep>(d.count())), locale(loc), negative(false) {
     if (d.count() < 0) {
       val = 0 - val;
       negative = true;
@@ -1821,24 +1640,21 @@ struct chrono_formatter {
     // this may overflow and/or the result may not fit in the
     // target type.
     // might need checked conversion (rep!=Rep)
-    s = fmt_duration_cast<seconds>(std::chrono::duration<rep, Period>(val));
+    s = detail::duration_cast<seconds>(std::chrono::duration<rep, Period>(val));
   }
 
   // returns true if nan or inf, writes to out.
   auto handle_nan_inf() -> bool {
-    if (isfinite(val)) {
-      return false;
-    }
+    if (isfinite(val)) return false;
     if (isnan(val)) {
       write_nan();
       return true;
     }
     // must be +-inf
-    if (val > 0) {
-      write_pinf();
-    } else {
-      write_ninf();
-    }
+    if (val > 0)
+      std::copy_n("inf", 3, out);
+    else
+      std::copy_n("-inf", 4, out);
     return true;
   }
 
@@ -1866,10 +1682,9 @@ struct chrono_formatter {
   }
 
   void write_sign() {
-    if (negative) {
-      *out++ = '-';
-      negative = false;
-    }
+    if (!negative) return;
+    *out++ = '-';
+    negative = false;
   }
 
   void write(Rep value, int width, pad_type pad = pad_type::zero) {
@@ -1881,24 +1696,22 @@ struct chrono_formatter {
     if (width > num_digits) {
       out = detail::write_padding(out, pad, width - num_digits);
     }
-    out = format_decimal<char_type>(out, n, num_digits).end;
+    out = format_decimal<Char>(out, n, num_digits);
   }
 
   void write_nan() { std::copy_n("nan", 3, out); }
-  void write_pinf() { std::copy_n("inf", 3, out); }
-  void write_ninf() { std::copy_n("-inf", 4, out); }
 
   template <typename Callback, typename... Args>
   void format_tm(const tm& time, Callback cb, Args... args) {
     if (isnan(val)) return write_nan();
-    get_locale loc(localized, context.locale());
+    get_locale loc(localized, locale);
     auto w = tm_writer_type(loc, out, time);
     (w.*cb)(args...);
     out = w.out();
   }
 
-  void on_text(const char_type* begin, const char_type* end) {
-    std::copy(begin, end, out);
+  void on_text(const Char* begin, const Char* end) {
+    copy<Char>(begin, end, out);
   }
 
   // These are not implemented because durations don't have date information.
@@ -1915,19 +1728,19 @@ struct chrono_formatter {
   void on_iso_date() {}
   void on_utc_offset(numeric_system) {}
   void on_tz_name() {}
-  void on_year(numeric_system) {}
+  void on_year(numeric_system, pad_type) {}
   void on_short_year(numeric_system) {}
   void on_offset_year() {}
   void on_century(numeric_system) {}
   void on_iso_week_based_year() {}
   void on_iso_week_based_short_year() {}
-  void on_dec_month(numeric_system) {}
+  void on_dec_month(numeric_system, pad_type) {}
   void on_dec0_week_of_year(numeric_system, pad_type) {}
   void on_dec1_week_of_year(numeric_system, pad_type) {}
   void on_iso_week_of_year(numeric_system, pad_type) {}
   void on_day_of_month(numeric_system, pad_type) {}
 
-  void on_day_of_year() {
+  void on_day_of_year(pad_type) {
     if (handle_nan_inf()) return;
     write(days(), 0);
   }
@@ -1968,13 +1781,12 @@ struct chrono_formatter {
         write_floating_seconds(buf, std::chrono::duration<rep, Period>(val),
                                precision);
         if (negative) *out++ = '-';
-        if (buf.size() < 2 || buf[1] == '.') {
+        if (buf.size() < 2 || buf[1] == '.')
           out = detail::write_padding(out, pad);
-        }
-        out = std::copy(buf.begin(), buf.end(), out);
+        out = copy<Char>(buf.begin(), buf.end(), out);
       } else {
         write(second(), 2, pad);
-        write_fractional_seconds<char_type>(
+        write_fractional_seconds<Char>(
             out, std::chrono::duration<rep, Period>(val), precision);
       }
       return;
@@ -2016,12 +1828,10 @@ struct chrono_formatter {
   void on_duration_value() {
     if (handle_nan_inf()) return;
     write_sign();
-    out = format_duration_value<char_type>(out, val, precision);
+    out = format_duration_value<Char>(out, val, precision);
   }
 
-  void on_duration_unit() {
-    out = format_duration_unit<char_type, Period>(out);
-  }
+  void on_duration_unit() { out = format_duration_unit<Char, Period>(out); }
 };
 
 }  // namespace detail
@@ -2091,22 +1901,19 @@ class year_month_day {
   constexpr auto month() const noexcept -> fmt::month { return month_; }
   constexpr auto day() const noexcept -> fmt::day { return day_; }
 };
-#endif
+#endif  // __cpp_lib_chrono >= 201907
 
 template <typename Char>
 struct formatter<weekday, Char> : private formatter<std::tm, Char> {
  private:
-  bool localized_ = false;
   bool use_tm_formatter_ = false;
 
  public:
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     auto it = ctx.begin(), end = ctx.end();
     if (it != end && *it == 'L') {
       ++it;
-      localized_ = true;
-      return it;
+      this->set_localized();
     }
     use_tm_formatter_ = it != end && *it != '}';
     return use_tm_formatter_ ? formatter<std::tm, Char>::parse(ctx) : it;
@@ -2117,7 +1924,7 @@ struct formatter<weekday, Char> : private formatter<std::tm, Char> {
     auto time = std::tm();
     time.tm_wday = static_cast<int>(wd.c_encoding());
     if (use_tm_formatter_) return formatter<std::tm, Char>::format(time, ctx);
-    detail::get_locale loc(localized_, ctx.locale());
+    detail::get_locale loc(this->localized(), ctx.locale());
     auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
     w.on_abbr_weekday();
     return w.out();
@@ -2130,8 +1937,7 @@ struct formatter<day, Char> : private formatter<std::tm, Char> {
   bool use_tm_formatter_ = false;
 
  public:
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     auto it = ctx.begin(), end = ctx.end();
     use_tm_formatter_ = it != end && *it != '}';
     return use_tm_formatter_ ? formatter<std::tm, Char>::parse(ctx) : it;
@@ -2152,17 +1958,14 @@ struct formatter<day, Char> : private formatter<std::tm, Char> {
 template <typename Char>
 struct formatter<month, Char> : private formatter<std::tm, Char> {
  private:
-  bool localized_ = false;
   bool use_tm_formatter_ = false;
 
  public:
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     auto it = ctx.begin(), end = ctx.end();
     if (it != end && *it == 'L') {
       ++it;
-      localized_ = true;
-      return it;
+      this->set_localized();
     }
     use_tm_formatter_ = it != end && *it != '}';
     return use_tm_formatter_ ? formatter<std::tm, Char>::parse(ctx) : it;
@@ -2173,7 +1976,7 @@ struct formatter<month, Char> : private formatter<std::tm, Char> {
     auto time = std::tm();
     time.tm_mon = static_cast<int>(static_cast<unsigned>(m)) - 1;
     if (use_tm_formatter_) return formatter<std::tm, Char>::format(time, ctx);
-    detail::get_locale loc(localized_, ctx.locale());
+    detail::get_locale loc(this->localized(), ctx.locale());
     auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
     w.on_abbr_month();
     return w.out();
@@ -2186,8 +1989,7 @@ struct formatter<year, Char> : private formatter<std::tm, Char> {
   bool use_tm_formatter_ = false;
 
  public:
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     auto it = ctx.begin(), end = ctx.end();
     use_tm_formatter_ = it != end && *it != '}';
     return use_tm_formatter_ ? formatter<std::tm, Char>::parse(ctx) : it;
@@ -2200,7 +2002,7 @@ struct formatter<year, Char> : private formatter<std::tm, Char> {
     if (use_tm_formatter_) return formatter<std::tm, Char>::format(time, ctx);
     detail::get_locale loc(false, ctx.locale());
     auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
-    w.on_year(detail::numeric_system::standard);
+    w.on_year(detail::numeric_system::standard, detail::pad_type::zero);
     return w.out();
   }
 };
@@ -2211,8 +2013,7 @@ struct formatter<year_month_day, Char> : private formatter<std::tm, Char> {
   bool use_tm_formatter_ = false;
 
  public:
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     auto it = ctx.begin(), end = ctx.end();
     use_tm_formatter_ = it != end && *it != '}';
     return use_tm_formatter_ ? formatter<std::tm, Char>::parse(ctx) : it;
@@ -2239,33 +2040,33 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
   format_specs specs_;
   detail::arg_ref<Char> width_ref_;
   detail::arg_ref<Char> precision_ref_;
-  bool localized_ = false;
-  basic_string_view<Char> format_str_;
+  basic_string_view<Char> fmt_;
 
  public:
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     auto it = ctx.begin(), end = ctx.end();
     if (it == end || *it == '}') return it;
 
     it = detail::parse_align(it, end, specs_);
     if (it == end) return it;
 
-    it = detail::parse_dynamic_spec(it, end, specs_.width, width_ref_, ctx);
-    if (it == end) return it;
+    Char c = *it;
+    if ((c >= '0' && c <= '9') || c == '{') {
+      it = detail::parse_width(it, end, specs_, width_ref_, ctx);
+      if (it == end) return it;
+    }
 
     auto checker = detail::chrono_format_checker();
     if (*it == '.') {
       checker.has_precision_integral = !std::is_floating_point<Rep>::value;
-      it = detail::parse_precision(it, end, specs_.precision, precision_ref_,
-                                   ctx);
+      it = detail::parse_precision(it, end, specs_, precision_ref_, ctx);
     }
     if (it != end && *it == 'L') {
-      localized_ = true;
+      specs_.set_localized();
       ++it;
     }
     end = detail::parse_chrono_format(it, end, checker);
-    format_str_ = {it, detail::to_unsigned(end - it)};
+    fmt_ = {it, detail::to_unsigned(end - it)};
     return end;
   }
 
@@ -2275,24 +2076,23 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
     auto specs = specs_;
     auto precision = specs.precision;
     specs.precision = -1;
-    auto begin = format_str_.begin(), end = format_str_.end();
+    auto begin = fmt_.begin(), end = fmt_.end();
     // As a possible future optimization, we could avoid extra copying if width
     // is not specified.
     auto buf = basic_memory_buffer<Char>();
-    auto out = std::back_inserter(buf);
-    detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref_,
-                                                       ctx);
-    detail::handle_dynamic_spec<detail::precision_checker>(precision,
-                                                           precision_ref_, ctx);
+    auto out = basic_appender<Char>(buf);
+    detail::handle_dynamic_spec(specs.dynamic_width(), specs.width, width_ref_,
+                                ctx);
+    detail::handle_dynamic_spec(specs.dynamic_precision(), precision,
+                                precision_ref_, ctx);
     if (begin == end || *begin == '}') {
       out = detail::format_duration_value<Char>(out, d.count(), precision);
       detail::format_duration_unit<Char, Period>(out);
     } else {
-      using chrono_formatter =
-          detail::chrono_formatter<FormatContext, decltype(out), Rep, Period>;
-      auto f = chrono_formatter(ctx, out, d);
+      auto f =
+          detail::duration_formatter<Char, Rep, Period>(out, d, ctx.locale());
       f.precision = precision;
-      f.localized = localized_;
+      f.localized = specs_.localized();
       detail::parse_chrono_format(begin, end, f);
     }
     return detail::write(
@@ -2300,129 +2100,143 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
   }
 };
 
+template <typename Char> struct formatter<std::tm, Char> {
+ private:
+  format_specs specs_;
+  detail::arg_ref<Char> width_ref_;
+  basic_string_view<Char> fmt_ =
+      detail::string_literal<Char, '%', 'F', ' ', '%', 'T'>();
+
+ protected:
+  auto localized() const -> bool { return specs_.localized(); }
+  FMT_CONSTEXPR void set_localized() { specs_.set_localized(); }
+
+  FMT_CONSTEXPR auto do_parse(parse_context<Char>& ctx, bool has_timezone)
+      -> const Char* {
+    auto it = ctx.begin(), end = ctx.end();
+    if (it == end || *it == '}') return it;
+
+    it = detail::parse_align(it, end, specs_);
+    if (it == end) return it;
+
+    Char c = *it;
+    if ((c >= '0' && c <= '9') || c == '{') {
+      it = detail::parse_width(it, end, specs_, width_ref_, ctx);
+      if (it == end) return it;
+    }
+
+    if (*it == 'L') {
+      specs_.set_localized();
+      ++it;
+    }
+
+    end = detail::parse_chrono_format(it, end,
+                                      detail::tm_format_checker(has_timezone));
+    // Replace the default format string only if the new spec is not empty.
+    if (end != it) fmt_ = {it, detail::to_unsigned(end - it)};
+    return end;
+  }
+
+  template <typename Duration, typename FormatContext>
+  auto do_format(const std::tm& tm, FormatContext& ctx,
+                 const Duration* subsecs) const -> decltype(ctx.out()) {
+    auto specs = specs_;
+    auto buf = basic_memory_buffer<Char>();
+    auto out = basic_appender<Char>(buf);
+    detail::handle_dynamic_spec(specs.dynamic_width(), specs.width, width_ref_,
+                                ctx);
+
+    auto loc_ref = specs.localized() ? ctx.locale() : locale_ref();
+    detail::get_locale loc(static_cast<bool>(loc_ref), loc_ref);
+    auto w = detail::tm_writer<basic_appender<Char>, Char, Duration>(
+        loc, out, tm, subsecs);
+    detail::parse_chrono_format(fmt_.begin(), fmt_.end(), w);
+    return detail::write(
+        ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
+  }
+
+ public:
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+    return do_parse(ctx, detail::has_tm_gmtoff<std::tm>::value);
+  }
+
+  template <typename FormatContext>
+  auto format(const std::tm& tm, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return do_format<std::chrono::seconds>(tm, ctx, nullptr);
+  }
+};
+
+// DEPRECATED! Reversed order of template parameters.
 template <typename Char, typename Duration>
-struct formatter<std::chrono::time_point<std::chrono::system_clock, Duration>,
-                 Char> : formatter<std::tm, Char> {
-  FMT_CONSTEXPR formatter() {
-    this->format_str_ = detail::string_literal<Char, '%', 'F', ' ', '%', 'T'>{};
+struct formatter<sys_time<Duration>, Char> : private formatter<std::tm, Char> {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+    return this->do_parse(ctx, true);
   }
 
   template <typename FormatContext>
-  auto format(std::chrono::time_point<std::chrono::system_clock, Duration> val,
-              FormatContext& ctx) const -> decltype(ctx.out()) {
+  auto format(sys_time<Duration> val, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
     std::tm tm = gmtime(val);
     using period = typename Duration::period;
     if (detail::const_check(
             period::num == 1 && period::den == 1 &&
             !std::is_floating_point<typename Duration::rep>::value)) {
+      detail::set_tm_zone(tm, detail::utc());
       return formatter<std::tm, Char>::format(tm, ctx);
     }
     Duration epoch = val.time_since_epoch();
-    Duration subsecs = detail::fmt_duration_cast<Duration>(
-        epoch - detail::fmt_duration_cast<std::chrono::seconds>(epoch));
+    Duration subsecs = detail::duration_cast<Duration>(
+        epoch - detail::duration_cast<std::chrono::seconds>(epoch));
     if (subsecs.count() < 0) {
-      auto second =
-          detail::fmt_duration_cast<Duration>(std::chrono::seconds(1));
-      if (tm.tm_sec != 0)
+      auto second = detail::duration_cast<Duration>(std::chrono::seconds(1));
+      if (tm.tm_sec != 0) {
         --tm.tm_sec;
-      else
+      } else {
         tm = gmtime(val - second);
-      subsecs += detail::fmt_duration_cast<Duration>(std::chrono::seconds(1));
+        detail::set_tm_zone(tm, detail::utc());
+      }
+      subsecs += second;
     }
     return formatter<std::tm, Char>::do_format(tm, ctx, &subsecs);
   }
 };
 
-#if FMT_USE_LOCAL_TIME
-template <typename Char, typename Duration>
-struct formatter<std::chrono::local_time<Duration>, Char>
-    : formatter<std::tm, Char> {
-  FMT_CONSTEXPR formatter() {
-    this->format_str_ = detail::string_literal<Char, '%', 'F', ' ', '%', 'T'>{};
-  }
-
+template <typename Duration, typename Char>
+struct formatter<utc_time<Duration>, Char>
+    : formatter<sys_time<Duration>, Char> {
   template <typename FormatContext>
-  auto format(std::chrono::local_time<Duration> val, FormatContext& ctx) const
+  auto format(utc_time<Duration> val, FormatContext& ctx) const
       -> decltype(ctx.out()) {
-    using period = typename Duration::period;
-    if (period::num != 1 || period::den != 1 ||
-        std::is_floating_point<typename Duration::rep>::value) {
-      const auto epoch = val.time_since_epoch();
-      const auto subsecs = detail::fmt_duration_cast<Duration>(
-          epoch - detail::fmt_duration_cast<std::chrono::seconds>(epoch));
-
-      return formatter<std::tm, Char>::do_format(localtime(val), ctx, &subsecs);
-    }
-
-    return formatter<std::tm, Char>::format(localtime(val), ctx);
+    return formatter<sys_time<Duration>, Char>::format(
+        detail::utc_clock::to_sys(val), ctx);
   }
 };
-#endif
 
-#if FMT_USE_UTC_TIME
-template <typename Char, typename Duration>
-struct formatter<std::chrono::time_point<std::chrono::utc_clock, Duration>,
-                 Char>
-    : formatter<std::chrono::time_point<std::chrono::system_clock, Duration>,
-                Char> {
-  template <typename FormatContext>
-  auto format(std::chrono::time_point<std::chrono::utc_clock, Duration> val,
-              FormatContext& ctx) const -> decltype(ctx.out()) {
-    return formatter<
-        std::chrono::time_point<std::chrono::system_clock, Duration>,
-        Char>::format(std::chrono::utc_clock::to_sys(val), ctx);
-  }
-};
-#endif
-
-template <typename Char> struct formatter<std::tm, Char> {
- private:
-  format_specs specs_;
-  detail::arg_ref<Char> width_ref_;
-
- protected:
-  basic_string_view<Char> format_str_;
-
-  template <typename FormatContext, typename Duration>
-  auto do_format(const std::tm& tm, FormatContext& ctx,
-                 const Duration* subsecs) const -> decltype(ctx.out()) {
-    auto specs = specs_;
-    auto buf = basic_memory_buffer<Char>();
-    auto out = std::back_inserter(buf);
-    detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref_,
-                                                       ctx);
-
-    auto loc_ref = ctx.locale();
-    detail::get_locale loc(static_cast<bool>(loc_ref), loc_ref);
-    auto w =
-        detail::tm_writer<decltype(out), Char, Duration>(loc, out, tm, subsecs);
-    detail::parse_chrono_format(format_str_.begin(), format_str_.end(), w);
-    return detail::write(
-        ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
-  }
-
- public:
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
-    auto it = ctx.begin(), end = ctx.end();
-    if (it == end || *it == '}') return it;
-
-    it = detail::parse_align(it, end, specs_);
-    if (it == end) return it;
-
-    it = detail::parse_dynamic_spec(it, end, specs_.width, width_ref_, ctx);
-    if (it == end) return it;
-
-    end = detail::parse_chrono_format(it, end, detail::tm_format_checker());
-    // Replace the default format_str only if the new spec is not empty.
-    if (end != it) format_str_ = {it, detail::to_unsigned(end - it)};
-    return end;
+template <typename Duration, typename Char>
+struct formatter<local_time<Duration>, Char>
+    : private formatter<std::tm, Char> {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+    return this->do_parse(ctx, false);
   }
 
   template <typename FormatContext>
-  auto format(const std::tm& tm, FormatContext& ctx) const
+  auto format(local_time<Duration> val, FormatContext& ctx) const
       -> decltype(ctx.out()) {
-    return do_format<FormatContext, std::chrono::seconds>(tm, ctx, nullptr);
+    auto time_since_epoch = val.time_since_epoch();
+    auto seconds_since_epoch =
+        detail::duration_cast<std::chrono::seconds>(time_since_epoch);
+    // Use gmtime to prevent time zone conversion since local_time has an
+    // unspecified time zone.
+    std::tm t = gmtime(seconds_since_epoch.count());
+    using period = typename Duration::period;
+    if (period::num == 1 && period::den == 1 &&
+        !std::is_floating_point<typename Duration::rep>::value) {
+      return formatter<std::tm, Char>::format(t, ctx);
+    }
+    auto subsecs =
+        detail::duration_cast<Duration>(time_since_epoch - seconds_since_epoch);
+    return formatter<std::tm, Char>::do_format(t, ctx, &subsecs);
   }
 };
 
diff --git a/contrib/fmt/include/fmt/color.h b/contrib/fmt/include/fmt/color.h
index f0e9dd94ef..2cbc53ca30 100644
--- a/contrib/fmt/include/fmt/color.h
+++ b/contrib/fmt/include/fmt/color.h
@@ -190,11 +190,11 @@ enum class emphasis : uint8_t {
 // rgb is a struct for red, green and blue colors.
 // Using the name "rgb" makes some editors show the color in a tooltip.
 struct rgb {
-  FMT_CONSTEXPR rgb() : r(0), g(0), b(0) {}
-  FMT_CONSTEXPR rgb(uint8_t r_, uint8_t g_, uint8_t b_) : r(r_), g(g_), b(b_) {}
-  FMT_CONSTEXPR rgb(uint32_t hex)
+  constexpr rgb() : r(0), g(0), b(0) {}
+  constexpr rgb(uint8_t r_, uint8_t g_, uint8_t b_) : r(r_), g(g_), b(b_) {}
+  constexpr rgb(uint32_t hex)
       : r((hex >> 16) & 0xFF), g((hex >> 8) & 0xFF), b(hex & 0xFF) {}
-  FMT_CONSTEXPR rgb(color hex)
+  constexpr rgb(color hex)
       : r((uint32_t(hex) >> 16) & 0xFF),
         g((uint32_t(hex) >> 8) & 0xFF),
         b(uint32_t(hex) & 0xFF) {}
@@ -205,97 +205,135 @@ struct rgb {
 
 namespace detail {
 
-// color is a struct of either a rgb color or a terminal color.
+// A bit-packed variant of an RGB color, a terminal color, or unset color.
+// see text_style for the bit-packing scheme.
 struct color_type {
-  FMT_CONSTEXPR color_type() noexcept : is_rgb(), value{} {}
-  FMT_CONSTEXPR color_type(color rgb_color) noexcept : is_rgb(true), value{} {
-    value.rgb_color = static_cast<uint32_t>(rgb_color);
+  constexpr color_type() noexcept = default;
+  constexpr color_type(color rgb_color) noexcept
+      : value_(static_cast<uint32_t>(rgb_color) | (1 << 24)) {}
+  constexpr color_type(rgb rgb_color) noexcept
+      : color_type(static_cast<color>(
+            (static_cast<uint32_t>(rgb_color.r) << 16) |
+            (static_cast<uint32_t>(rgb_color.g) << 8) | rgb_color.b)) {}
+  constexpr color_type(terminal_color term_color) noexcept
+      : value_(static_cast<uint32_t>(term_color) | (3 << 24)) {}
+
+  constexpr auto is_terminal_color() const noexcept -> bool {
+    return (value_ & (1 << 25)) != 0;
   }
-  FMT_CONSTEXPR color_type(rgb rgb_color) noexcept : is_rgb(true), value{} {
-    value.rgb_color = (static_cast<uint32_t>(rgb_color.r) << 16) |
-                      (static_cast<uint32_t>(rgb_color.g) << 8) | rgb_color.b;
-  }
-  FMT_CONSTEXPR color_type(terminal_color term_color) noexcept
-      : is_rgb(), value{} {
-    value.term_color = static_cast<uint8_t>(term_color);
+
+  constexpr auto value() const noexcept -> uint32_t {
+    return value_ & 0xFFFFFF;
   }
-  bool is_rgb;
-  union color_union {
-    uint8_t term_color;
-    uint32_t rgb_color;
-  } value;
+
+  constexpr color_type(uint32_t value) noexcept : value_(value) {}
+
+  uint32_t value_ = 0;
 };
 }  // namespace detail
 
 /// A text style consisting of foreground and background colors and emphasis.
 class text_style {
+  // The information is packed as follows:
+  // ┌──┐
+  // │ 0│─┐
+  // │..│ ├── foreground color value
+  // │23│─┘
+  // ├──┤
+  // │24│─┬── discriminator for the above value. 00 if unset, 01 if it's
+  // │25│─┘   an RGB color, or 11 if it's a terminal color (10 is unused)
+  // ├──┤
+  // │26│──── overflow bit, always zero (see below)
+  // ├──┤
+  // │27│─┐
+  // │..│ │
+  // │50│ │
+  // ├──┤ │
+  // │51│ ├── background color (same format as the foreground color)
+  // │52│ │
+  // ├──┤ │
+  // │53│─┘
+  // ├──┤
+  // │54│─┐
+  // │..│ ├── emphases
+  // │61│─┘
+  // ├──┤
+  // │62│─┬── unused
+  // │63│─┘
+  // └──┘
+  // The overflow bits are there to make operator|= efficient.
+  // When ORing, we must throw if, for either the foreground or background,
+  // one style specifies a terminal color and the other specifies any color
+  // (terminal or RGB); in other words, if one discriminator is 11 and the
+  // other is 11 or 01.
+  //
+  // We do that check by adding the styles. Consider what adding does to each
+  // possible pair of discriminators:
+  //    00 + 00 = 000
+  //    01 + 00 = 001
+  //    11 + 00 = 011
+  //    01 + 01 = 010
+  //    11 + 01 = 100 (!!)
+  //    11 + 11 = 110 (!!)
+  // In the last two cases, the ones we want to catch, the third bit——the
+  // overflow bit——is set. Bingo.
+  //
+  // We must take into account the possible carry bit from the bits
+  // before the discriminator. The only potentially problematic case is
+  // 11 + 00 = 011 (a carry bit would make it 100, not good!), but a carry
+  // bit is impossible in that case, because 00 (unset color) means the
+  // 24 bits that precede the discriminator are all zero.
+  //
+  // This test can be applied to both colors simultaneously.
+
  public:
   FMT_CONSTEXPR text_style(emphasis em = emphasis()) noexcept
-      : set_foreground_color(), set_background_color(), ems(em) {}
-
-  FMT_CONSTEXPR auto operator|=(const text_style& rhs) -> text_style& {
-    if (!set_foreground_color) {
-      set_foreground_color = rhs.set_foreground_color;
-      foreground_color = rhs.foreground_color;
-    } else if (rhs.set_foreground_color) {
-      if (!foreground_color.is_rgb || !rhs.foreground_color.is_rgb)
-        report_error("can't OR a terminal color");
-      foreground_color.value.rgb_color |= rhs.foreground_color.value.rgb_color;
-    }
-
-    if (!set_background_color) {
-      set_background_color = rhs.set_background_color;
-      background_color = rhs.background_color;
-    } else if (rhs.set_background_color) {
-      if (!background_color.is_rgb || !rhs.background_color.is_rgb)
-        report_error("can't OR a terminal color");
-      background_color.value.rgb_color |= rhs.background_color.value.rgb_color;
-    }
+      : style_(static_cast<uint64_t>(em) << 54) {}
 
-    ems = static_cast<emphasis>(static_cast<uint8_t>(ems) |
-                                static_cast<uint8_t>(rhs.ems));
+  FMT_CONSTEXPR auto operator|=(text_style rhs) -> text_style& {
+    if (((style_ + rhs.style_) & ((1ULL << 26) | (1ULL << 53))) != 0)
+      report_error("can't OR a terminal color");
+    style_ |= rhs.style_;
     return *this;
   }
 
-  friend FMT_CONSTEXPR auto operator|(text_style lhs, const text_style& rhs)
+  friend FMT_CONSTEXPR auto operator|(text_style lhs, text_style rhs)
       -> text_style {
     return lhs |= rhs;
   }
 
+  FMT_CONSTEXPR auto operator==(text_style rhs) const noexcept -> bool {
+    return style_ == rhs.style_;
+  }
+
+  FMT_CONSTEXPR auto operator!=(text_style rhs) const noexcept -> bool {
+    return !(*this == rhs);
+  }
+
   FMT_CONSTEXPR auto has_foreground() const noexcept -> bool {
-    return set_foreground_color;
+    return (style_ & (1 << 24)) != 0;
   }
   FMT_CONSTEXPR auto has_background() const noexcept -> bool {
-    return set_background_color;
+    return (style_ & (1ULL << 51)) != 0;
   }
   FMT_CONSTEXPR auto has_emphasis() const noexcept -> bool {
-    return static_cast<uint8_t>(ems) != 0;
+    return (style_ >> 54) != 0;
   }
   FMT_CONSTEXPR auto get_foreground() const noexcept -> detail::color_type {
     FMT_ASSERT(has_foreground(), "no foreground specified for this style");
-    return foreground_color;
+    return style_ & 0x3FFFFFF;
   }
   FMT_CONSTEXPR auto get_background() const noexcept -> detail::color_type {
     FMT_ASSERT(has_background(), "no background specified for this style");
-    return background_color;
+    return (style_ >> 27) & 0x3FFFFFF;
   }
   FMT_CONSTEXPR auto get_emphasis() const noexcept -> emphasis {
     FMT_ASSERT(has_emphasis(), "no emphasis specified for this style");
-    return ems;
+    return static_cast<emphasis>(style_ >> 54);
   }
 
  private:
-  FMT_CONSTEXPR text_style(bool is_foreground,
-                           detail::color_type text_color) noexcept
-      : set_foreground_color(), set_background_color(), ems() {
-    if (is_foreground) {
-      foreground_color = text_color;
-      set_foreground_color = true;
-    } else {
-      background_color = text_color;
-      set_background_color = true;
-    }
-  }
+  FMT_CONSTEXPR text_style(uint64_t style) noexcept : style_(style) {}
 
   friend FMT_CONSTEXPR auto fg(detail::color_type foreground) noexcept
       -> text_style;
@@ -303,23 +341,19 @@ class text_style {
   friend FMT_CONSTEXPR auto bg(detail::color_type background) noexcept
       -> text_style;
 
-  detail::color_type foreground_color;
-  detail::color_type background_color;
-  bool set_foreground_color;
-  bool set_background_color;
-  emphasis ems;
+  uint64_t style_ = 0;
 };
 
 /// Creates a text style from the foreground (text) color.
 FMT_CONSTEXPR inline auto fg(detail::color_type foreground) noexcept
     -> text_style {
-  return text_style(true, foreground);
+  return foreground.value_;
 }
 
 /// Creates a text style from the background color.
 FMT_CONSTEXPR inline auto bg(detail::color_type background) noexcept
     -> text_style {
-  return text_style(false, background);
+  return static_cast<uint64_t>(background.value_) << 27;
 }
 
 FMT_CONSTEXPR inline auto operator|(emphasis lhs, emphasis rhs) noexcept
@@ -330,41 +364,39 @@ FMT_CONSTEXPR inline auto operator|(emphasis lhs, emphasis rhs) noexcept
 namespace detail {
 
 template <typename Char> struct ansi_color_escape {
-  FMT_CONSTEXPR ansi_color_escape(detail::color_type text_color,
+  FMT_CONSTEXPR ansi_color_escape(color_type text_color,
                                   const char* esc) noexcept {
     // If we have a terminal color, we need to output another escape code
     // sequence.
-    if (!text_color.is_rgb) {
+    if (text_color.is_terminal_color()) {
       bool is_background = esc == string_view("\x1b[48;2;");
-      uint32_t value = text_color.value.term_color;
+      uint32_t value = text_color.value();
       // Background ASCII codes are the same as the foreground ones but with
       // 10 more.
       if (is_background) value += 10u;
 
-      size_t index = 0;
-      buffer[index++] = static_cast<Char>('\x1b');
-      buffer[index++] = static_cast<Char>('[');
+      buffer[size++] = static_cast<Char>('\x1b');
+      buffer[size++] = static_cast<Char>('[');
 
       if (value >= 100u) {
-        buffer[index++] = static_cast<Char>('1');
+        buffer[size++] = static_cast<Char>('1');
         value %= 100u;
       }
-      buffer[index++] = static_cast<Char>('0' + value / 10u);
-      buffer[index++] = static_cast<Char>('0' + value % 10u);
+      buffer[size++] = static_cast<Char>('0' + value / 10u);
+      buffer[size++] = static_cast<Char>('0' + value % 10u);
 
-      buffer[index++] = static_cast<Char>('m');
-      buffer[index++] = static_cast<Char>('\0');
+      buffer[size++] = static_cast<Char>('m');
       return;
     }
 
     for (int i = 0; i < 7; i++) {
       buffer[i] = static_cast<Char>(esc[i]);
     }
-    rgb color(text_color.value.rgb_color);
+    rgb color(text_color.value());
     to_esc(color.r, buffer + 7, ';');
     to_esc(color.g, buffer + 11, ';');
     to_esc(color.b, buffer + 15, 'm');
-    buffer[19] = static_cast<Char>(0);
+    size = 19;
   }
   FMT_CONSTEXPR ansi_color_escape(emphasis em) noexcept {
     uint8_t em_codes[num_emphases] = {};
@@ -377,26 +409,28 @@ template <typename Char> struct ansi_color_escape {
     if (has_emphasis(em, emphasis::conceal)) em_codes[6] = 8;
     if (has_emphasis(em, emphasis::strikethrough)) em_codes[7] = 9;
 
-    size_t index = 0;
+    buffer[size++] = static_cast<Char>('\x1b');
+    buffer[size++] = static_cast<Char>('[');
+
     for (size_t i = 0; i < num_emphases; ++i) {
       if (!em_codes[i]) continue;
-      buffer[index++] = static_cast<Char>('\x1b');
-      buffer[index++] = static_cast<Char>('[');
-      buffer[index++] = static_cast<Char>('0' + em_codes[i]);
-      buffer[index++] = static_cast<Char>('m');
+      buffer[size++] = static_cast<Char>('0' + em_codes[i]);
+      buffer[size++] = static_cast<Char>(';');
     }
-    buffer[index++] = static_cast<Char>(0);
+
+    buffer[size - 1] = static_cast<Char>('m');
   }
   FMT_CONSTEXPR operator const Char*() const noexcept { return buffer; }
 
   FMT_CONSTEXPR auto begin() const noexcept -> const Char* { return buffer; }
-  FMT_CONSTEXPR20 auto end() const noexcept -> const Char* {
-    return buffer + basic_string_view<Char>(buffer).size();
+  FMT_CONSTEXPR auto end() const noexcept -> const Char* {
+    return buffer + size;
   }
 
  private:
   static constexpr size_t num_emphases = 8;
-  Char buffer[7u + 3u * num_emphases + 1u];
+  Char buffer[7u + 4u * num_emphases] = {};
+  size_t size = 0;
 
   static FMT_CONSTEXPR void to_esc(uint8_t c, Char* out,
                                    char delimiter) noexcept {
@@ -412,13 +446,13 @@ template <typename Char> struct ansi_color_escape {
 };
 
 template <typename Char>
-FMT_CONSTEXPR auto make_foreground_color(detail::color_type foreground) noexcept
+FMT_CONSTEXPR auto make_foreground_color(color_type foreground) noexcept
     -> ansi_color_escape<Char> {
   return ansi_color_escape<Char>(foreground, "\x1b[38;2;");
 }
 
 template <typename Char>
-FMT_CONSTEXPR auto make_background_color(detail::color_type background) noexcept
+FMT_CONSTEXPR auto make_background_color(color_type background) noexcept
     -> ansi_color_escape<Char> {
   return ansi_color_escape<Char>(background, "\x1b[48;2;");
 }
@@ -434,40 +468,33 @@ template <typename Char> inline void reset_color(buffer<Char>& buffer) {
   buffer.append(reset_color.begin(), reset_color.end());
 }
 
-template <typename T> struct styled_arg : detail::view {
+template <typename T> struct styled_arg : view {
   const T& value;
   text_style style;
   styled_arg(const T& v, text_style s) : value(v), style(s) {}
 };
 
 template <typename Char>
-void vformat_to(
-    buffer<Char>& buf, const text_style& ts, basic_string_view<Char> format_str,
-    basic_format_args<buffered_context<type_identity_t<Char>>> args) {
-  bool has_style = false;
+void vformat_to(buffer<Char>& buf, text_style ts, basic_string_view<Char> fmt,
+                basic_format_args<buffered_context<Char>> args) {
   if (ts.has_emphasis()) {
-    has_style = true;
-    auto emphasis = detail::make_emphasis<Char>(ts.get_emphasis());
+    auto emphasis = make_emphasis<Char>(ts.get_emphasis());
     buf.append(emphasis.begin(), emphasis.end());
   }
   if (ts.has_foreground()) {
-    has_style = true;
-    auto foreground = detail::make_foreground_color<Char>(ts.get_foreground());
+    auto foreground = make_foreground_color<Char>(ts.get_foreground());
     buf.append(foreground.begin(), foreground.end());
   }
   if (ts.has_background()) {
-    has_style = true;
-    auto background = detail::make_background_color<Char>(ts.get_background());
+    auto background = make_background_color<Char>(ts.get_background());
     buf.append(background.begin(), background.end());
   }
-  detail::vformat_to(buf, format_str, args, {});
-  if (has_style) detail::reset_color<Char>(buf);
+  vformat_to(buf, fmt, args);
+  if (ts != text_style()) reset_color<Char>(buf);
 }
-
 }  // namespace detail
 
-inline void vprint(FILE* f, const text_style& ts, string_view fmt,
-                   format_args args) {
+inline void vprint(FILE* f, text_style ts, string_view fmt, format_args args) {
   auto buf = memory_buffer();
   detail::vformat_to(buf, ts, fmt, args);
   print(f, FMT_STRING("{}"), string_view(buf.begin(), buf.size()));
@@ -483,9 +510,8 @@ inline void vprint(FILE* f, const text_style& ts, string_view fmt,
  *                "Elapsed time: {0:.2f} seconds", 1.23);
  */
 template <typename... T>
-void print(FILE* f, const text_style& ts, format_string<T...> fmt,
-           T&&... args) {
-  vprint(f, ts, fmt, fmt::make_format_args(args...));
+void print(FILE* f, text_style ts, format_string<T...> fmt, T&&... args) {
+  vprint(f, ts, fmt.str, vargs<T...>{{args...}});
 }
 
 /**
@@ -498,11 +524,11 @@ void print(FILE* f, const text_style& ts, format_string<T...> fmt,
  *                "Elapsed time: {0:.2f} seconds", 1.23);
  */
 template <typename... T>
-void print(const text_style& ts, format_string<T...> fmt, T&&... args) {
+void print(text_style ts, format_string<T...> fmt, T&&... args) {
   return print(stdout, ts, fmt, std::forward<T>(args)...);
 }
 
-inline auto vformat(const text_style& ts, string_view fmt, format_args args)
+inline auto vformat(text_style ts, string_view fmt, format_args args)
     -> std::string {
   auto buf = memory_buffer();
   detail::vformat_to(buf, ts, fmt, args);
@@ -522,16 +548,16 @@ inline auto vformat(const text_style& ts, string_view fmt, format_args args)
  * ```
  */
 template <typename... T>
-inline auto format(const text_style& ts, format_string<T...> fmt, T&&... args)
+inline auto format(text_style ts, format_string<T...> fmt, T&&... args)
     -> std::string {
-  return fmt::vformat(ts, fmt, fmt::make_format_args(args...));
+  return fmt::vformat(ts, fmt.str, vargs<T...>{{args...}});
 }
 
 /// Formats a string with the given text_style and writes the output to `out`.
 template <typename OutputIt,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
-auto vformat_to(OutputIt out, const text_style& ts, string_view fmt,
-                format_args args) -> OutputIt {
+auto vformat_to(OutputIt out, text_style ts, string_view fmt, format_args args)
+    -> OutputIt {
   auto&& buf = detail::get_buffer<char>(out);
   detail::vformat_to(buf, ts, fmt, args);
   return detail::get_iterator(buf, out);
@@ -549,9 +575,9 @@ auto vformat_to(OutputIt out, const text_style& ts, string_view fmt,
  */
 template <typename OutputIt, typename... T,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
-inline auto format_to(OutputIt out, const text_style& ts,
-                      format_string<T...> fmt, T&&... args) -> OutputIt {
-  return vformat_to(out, ts, fmt, fmt::make_format_args(args...));
+inline auto format_to(OutputIt out, text_style ts, format_string<T...> fmt,
+                      T&&... args) -> OutputIt {
+  return vformat_to(out, ts, fmt.str, vargs<T...>{{args...}});
 }
 
 template <typename T, typename Char>
@@ -560,31 +586,30 @@ struct formatter<detail::styled_arg<T>, Char> : formatter<T, Char> {
   auto format(const detail::styled_arg<T>& arg, FormatContext& ctx) const
       -> decltype(ctx.out()) {
     const auto& ts = arg.style;
-    const auto& value = arg.value;
     auto out = ctx.out();
 
     bool has_style = false;
     if (ts.has_emphasis()) {
       has_style = true;
       auto emphasis = detail::make_emphasis<Char>(ts.get_emphasis());
-      out = std::copy(emphasis.begin(), emphasis.end(), out);
+      out = detail::copy<Char>(emphasis.begin(), emphasis.end(), out);
     }
     if (ts.has_foreground()) {
       has_style = true;
       auto foreground =
           detail::make_foreground_color<Char>(ts.get_foreground());
-      out = std::copy(foreground.begin(), foreground.end(), out);
+      out = detail::copy<Char>(foreground.begin(), foreground.end(), out);
     }
     if (ts.has_background()) {
       has_style = true;
       auto background =
           detail::make_background_color<Char>(ts.get_background());
-      out = std::copy(background.begin(), background.end(), out);
+      out = detail::copy<Char>(background.begin(), background.end(), out);
     }
-    out = formatter<T, Char>::format(value, ctx);
+    out = formatter<T, Char>::format(arg.value, ctx);
     if (has_style) {
       auto reset_color = string_view("\x1b[0m");
-      out = std::copy(reset_color.begin(), reset_color.end(), out);
+      out = detail::copy<Char>(reset_color.begin(), reset_color.end(), out);
     }
     return out;
   }
diff --git a/contrib/fmt/include/fmt/compile.h b/contrib/fmt/include/fmt/compile.h
index b2afc2c309..64eb7a20dc 100644
--- a/contrib/fmt/include/fmt/compile.h
+++ b/contrib/fmt/include/fmt/compile.h
@@ -15,17 +15,10 @@
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
+FMT_BEGIN_EXPORT
 
 // A compile-time string which is compiled into fast formatting code.
-FMT_EXPORT class compiled_string {};
-
-namespace detail {
-
-template <typename T, typename InputIt>
-FMT_CONSTEXPR inline auto copy(InputIt begin, InputIt end, counting_iterator it)
-    -> counting_iterator {
-  return it + (end - begin);
-}
+class compiled_string {};
 
 template <typename S>
 struct is_compiled_string : std::is_base_of<compiled_string, S> {};
@@ -42,34 +35,47 @@ struct is_compiled_string : std::is_base_of<compiled_string, S> {};
  *     std::string s = fmt::format(FMT_COMPILE("{}"), 42);
  */
 #if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
-#  define FMT_COMPILE(s) FMT_STRING_IMPL(s, fmt::compiled_string, explicit)
+#  define FMT_COMPILE(s) FMT_STRING_IMPL(s, fmt::compiled_string)
 #else
 #  define FMT_COMPILE(s) FMT_STRING(s)
 #endif
 
+/**
+ * Converts a string literal into a format string that will be parsed at
+ * compile time and converted into efficient formatting code. Requires support
+ * for class types in constant template parameters (a C++20 feature).
+ *
+ *  **Example**:
+ *
+ *     // Converts 42 into std::string using the most efficient method and no
+ *     // runtime format string processing.
+ *     using namespace fmt::literals;
+ *     std::string s = fmt::format("{}"_cf, 42);
+ */
 #if FMT_USE_NONTYPE_TEMPLATE_ARGS
-template <typename Char, size_t N,
-          fmt::detail_exported::fixed_string<Char, N> Str>
-struct udl_compiled_string : compiled_string {
-  using char_type = Char;
-  explicit constexpr operator basic_string_view<char_type>() const {
-    return {Str.data, N - 1};
-  }
-};
+inline namespace literals {
+template <detail::fixed_string Str> constexpr auto operator""_cf() {
+  return FMT_COMPILE(Str.data);
+}
+}  // namespace literals
 #endif
 
+FMT_END_EXPORT
+
+namespace detail {
+
 template <typename T, typename... Tail>
-auto first(const T& value, const Tail&...) -> const T& {
+constexpr auto first(const T& value, const Tail&...) -> const T& {
   return value;
 }
 
 #if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
-template <typename... Args> struct type_list {};
+template <typename... T> struct type_list {};
 
 // Returns a reference to the argument at index N from [first, rest...].
 template <int N, typename T, typename... Args>
-constexpr const auto& get([[maybe_unused]] const T& first,
-                          [[maybe_unused]] const Args&... rest) {
+constexpr auto get([[maybe_unused]] const T& first,
+                   [[maybe_unused]] const Args&... rest) -> const auto& {
   static_assert(N < 1 + sizeof...(Args), "index is out of bounds");
   if constexpr (N == 0)
     return first;
@@ -77,9 +83,32 @@ constexpr const auto& get([[maybe_unused]] const T& first,
     return detail::get<N - 1>(rest...);
 }
 
+#  if FMT_USE_NONTYPE_TEMPLATE_ARGS
+template <int N, typename T, typename... Args, typename Char>
+constexpr auto get_arg_index_by_name(basic_string_view<Char> name) -> int {
+  if constexpr (is_static_named_arg<T>()) {
+    if (name == T::name) return N;
+  }
+  if constexpr (sizeof...(Args) > 0)
+    return get_arg_index_by_name<N + 1, Args...>(name);
+  (void)name;  // Workaround an MSVC bug about "unused" parameter.
+  return -1;
+}
+#  endif
+
+template <typename... Args, typename Char>
+FMT_CONSTEXPR auto get_arg_index_by_name(basic_string_view<Char> name) -> int {
+#  if FMT_USE_NONTYPE_TEMPLATE_ARGS
+  if constexpr (sizeof...(Args) > 0)
+    return get_arg_index_by_name<0, Args...>(name);
+#  endif
+  (void)name;
+  return -1;
+}
+
 template <typename Char, typename... Args>
-constexpr int get_arg_index_by_name(basic_string_view<Char> name,
-                                    type_list<Args...>) {
+constexpr auto get_arg_index_by_name(basic_string_view<Char> name,
+                                     type_list<Args...>) -> int {
   return get_arg_index_by_name<Args...>(name);
 }
 
@@ -99,8 +128,8 @@ template <typename Char> struct text {
   basic_string_view<Char> data;
   using char_type = Char;
 
-  template <typename OutputIt, typename... Args>
-  constexpr OutputIt format(OutputIt out, const Args&...) const {
+  template <typename OutputIt, typename... T>
+  constexpr auto format(OutputIt out, const T&...) const -> OutputIt {
     return write<Char>(out, data);
   }
 };
@@ -109,8 +138,8 @@ template <typename Char>
 struct is_compiled_format<text<Char>> : std::true_type {};
 
 template <typename Char>
-constexpr text<Char> make_text(basic_string_view<Char> s, size_t pos,
-                               size_t size) {
+constexpr auto make_text(basic_string_view<Char> s, size_t pos, size_t size)
+    -> text<Char> {
   return {{&s[pos], size}};
 }
 
@@ -118,8 +147,8 @@ template <typename Char> struct code_unit {
   Char value;
   using char_type = Char;
 
-  template <typename OutputIt, typename... Args>
-  constexpr OutputIt format(OutputIt out, const Args&...) const {
+  template <typename OutputIt, typename... T>
+  constexpr auto format(OutputIt out, const T&...) const -> OutputIt {
     *out++ = value;
     return out;
   }
@@ -127,7 +156,7 @@ template <typename Char> struct code_unit {
 
 // This ensures that the argument type is convertible to `const T&`.
 template <typename T, int N, typename... Args>
-constexpr const T& get_arg_checked(const Args&... args) {
+constexpr auto get_arg_checked(const Args&... args) -> const T& {
   const auto& arg = detail::get<N>(args...);
   if constexpr (detail::is_named_arg<remove_cvref_t<decltype(arg)>>()) {
     return arg.value;
@@ -140,17 +169,18 @@ template <typename Char>
 struct is_compiled_format<code_unit<Char>> : std::true_type {};
 
 // A replacement field that refers to argument N.
-template <typename Char, typename T, int N> struct field {
+template <typename Char, typename V, int N> struct field {
   using char_type = Char;
 
-  template <typename OutputIt, typename... Args>
-  constexpr OutputIt format(OutputIt out, const Args&... args) const {
-    const T& arg = get_arg_checked<T, N>(args...);
-    if constexpr (std::is_convertible<T, basic_string_view<Char>>::value) {
+  template <typename OutputIt, typename... T>
+  constexpr auto format(OutputIt out, const T&... args) const -> OutputIt {
+    const V& arg = get_arg_checked<V, N>(args...);
+    if constexpr (std::is_convertible<V, basic_string_view<Char>>::value) {
       auto s = basic_string_view<Char>(arg);
       return copy<Char>(s.begin(), s.end(), out);
+    } else {
+      return write<Char>(out, arg);
     }
-    return write<Char>(out, arg);
   }
 };
 
@@ -163,10 +193,10 @@ template <typename Char> struct runtime_named_field {
   basic_string_view<Char> name;
 
   template <typename OutputIt, typename T>
-  constexpr static bool try_format_argument(
+  constexpr static auto try_format_argument(
       OutputIt& out,
       // [[maybe_unused]] due to unused-but-set-parameter warning in GCC 7,8,9
-      [[maybe_unused]] basic_string_view<Char> arg_name, const T& arg) {
+      [[maybe_unused]] basic_string_view<Char> arg_name, const T& arg) -> bool {
     if constexpr (is_named_arg<typename std::remove_cv<T>::type>::value) {
       if (arg_name == arg.name) {
         out = write<Char>(out, arg.value);
@@ -176,8 +206,8 @@ template <typename Char> struct runtime_named_field {
     return false;
   }
 
-  template <typename OutputIt, typename... Args>
-  constexpr OutputIt format(OutputIt out, const Args&... args) const {
+  template <typename OutputIt, typename... T>
+  constexpr auto format(OutputIt out, const T&... args) const -> OutputIt {
     bool found = (try_format_argument(out, name, args) || ...);
     if (!found) {
       FMT_THROW(format_error("argument with specified name is not found"));
@@ -190,17 +220,17 @@ template <typename Char>
 struct is_compiled_format<runtime_named_field<Char>> : std::true_type {};
 
 // A replacement field that refers to argument N and has format specifiers.
-template <typename Char, typename T, int N> struct spec_field {
+template <typename Char, typename V, int N> struct spec_field {
   using char_type = Char;
-  formatter<T, Char> fmt;
+  formatter<V, Char> fmt;
 
-  template <typename OutputIt, typename... Args>
-  constexpr FMT_INLINE OutputIt format(OutputIt out,
-                                       const Args&... args) const {
+  template <typename OutputIt, typename... T>
+  constexpr FMT_INLINE auto format(OutputIt out, const T&... args) const
+      -> OutputIt {
     const auto& vargs =
         fmt::make_format_args<basic_format_context<OutputIt, Char>>(args...);
     basic_format_context<OutputIt, Char> ctx(out, vargs);
-    return fmt.format(get_arg_checked<T, N>(args...), ctx);
+    return fmt.format(get_arg_checked<V, N>(args...), ctx);
   }
 };
 
@@ -212,8 +242,8 @@ template <typename L, typename R> struct concat {
   R rhs;
   using char_type = typename L::char_type;
 
-  template <typename OutputIt, typename... Args>
-  constexpr OutputIt format(OutputIt out, const Args&... args) const {
+  template <typename OutputIt, typename... T>
+  constexpr auto format(OutputIt out, const T&... args) const -> OutputIt {
     out = lhs.format(out, args...);
     return rhs.format(out, args...);
   }
@@ -223,14 +253,14 @@ template <typename L, typename R>
 struct is_compiled_format<concat<L, R>> : std::true_type {};
 
 template <typename L, typename R>
-constexpr concat<L, R> make_concat(L lhs, R rhs) {
+constexpr auto make_concat(L lhs, R rhs) -> concat<L, R> {
   return {lhs, rhs};
 }
 
 struct unknown_format {};
 
 template <typename Char>
-constexpr size_t parse_text(basic_string_view<Char> str, size_t pos) {
+constexpr auto parse_text(basic_string_view<Char> str, size_t pos) -> size_t {
   for (size_t size = str.size(); pos != size; ++pos) {
     if (str[pos] == '{' || str[pos] == '}') break;
   }
@@ -263,8 +293,8 @@ template <typename T, typename Char> struct parse_specs_result {
 enum { manual_indexing_id = -1 };
 
 template <typename T, typename Char>
-constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
-                                                  size_t pos, int next_arg_id) {
+constexpr auto parse_specs(basic_string_view<Char> str, size_t pos,
+                           int next_arg_id) -> parse_specs_result<T, Char> {
   str.remove_prefix(pos);
   auto ctx =
       compile_parse_context<Char>(str, max_value<int>(), nullptr, next_arg_id);
@@ -275,32 +305,36 @@ constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
 }
 
 template <typename Char> struct arg_id_handler {
+  arg_id_kind kind;
   arg_ref<Char> arg_id;
 
-  constexpr int on_auto() {
+  constexpr auto on_auto() -> int {
     FMT_ASSERT(false, "handler cannot be used with automatic indexing");
     return 0;
   }
-  constexpr int on_index(int id) {
+  constexpr auto on_index(int id) -> int {
+    kind = arg_id_kind::index;
     arg_id = arg_ref<Char>(id);
     return 0;
   }
-  constexpr int on_name(basic_string_view<Char> id) {
+  constexpr auto on_name(basic_string_view<Char> id) -> int {
+    kind = arg_id_kind::name;
     arg_id = arg_ref<Char>(id);
     return 0;
   }
 };
 
 template <typename Char> struct parse_arg_id_result {
+  arg_id_kind kind;
   arg_ref<Char> arg_id;
   const Char* arg_id_end;
 };
 
 template <int ID, typename Char>
 constexpr auto parse_arg_id(const Char* begin, const Char* end) {
-  auto handler = arg_id_handler<Char>{arg_ref<Char>{}};
+  auto handler = arg_id_handler<Char>{arg_id_kind::none, arg_ref<Char>{}};
   auto arg_id_end = parse_arg_id(begin, end, handler);
-  return parse_arg_id_result<Char>{handler.arg_id, arg_id_end};
+  return parse_arg_id_result<Char>{handler.kind, handler.arg_id, arg_id_end};
 }
 
 template <typename T, typename Enable = void> struct field_type {
@@ -363,18 +397,18 @@ constexpr auto compile_format_string(S fmt) {
       constexpr char_type c =
           arg_id_end_pos != str.size() ? str[arg_id_end_pos] : char_type();
       static_assert(c == '}' || c == ':', "missing '}' in format string");
-      if constexpr (arg_id_result.arg_id.kind == arg_id_kind::index) {
+      if constexpr (arg_id_result.kind == arg_id_kind::index) {
         static_assert(
             ID == manual_indexing_id || ID == 0,
             "cannot switch from automatic to manual argument indexing");
-        constexpr auto arg_index = arg_id_result.arg_id.val.index;
+        constexpr auto arg_index = arg_id_result.arg_id.index;
         return parse_replacement_field_then_tail<get_type<arg_index, Args>,
                                                  Args, arg_id_end_pos,
                                                  arg_index, manual_indexing_id>(
             fmt);
-      } else if constexpr (arg_id_result.arg_id.kind == arg_id_kind::name) {
+      } else if constexpr (arg_id_result.kind == arg_id_kind::name) {
         constexpr auto arg_index =
-            get_arg_index_by_name(arg_id_result.arg_id.val.name, Args{});
+            get_arg_index_by_name(arg_id_result.arg_id.name, Args{});
         if constexpr (arg_index >= 0) {
           constexpr auto next_id =
               ID != manual_indexing_id ? ID + 1 : manual_indexing_id;
@@ -383,8 +417,7 @@ constexpr auto compile_format_string(S fmt) {
               arg_index, next_id>(fmt);
         } else if constexpr (c == '}') {
           return parse_tail<Args, arg_id_end_pos + 1, ID>(
-              runtime_named_field<char_type>{arg_id_result.arg_id.val.name},
-              fmt);
+              runtime_named_field<char_type>{arg_id_result.arg_id.name}, fmt);
         } else if constexpr (c == ':') {
           return unknown_format();  // no type info for specs parsing
         }
@@ -405,7 +438,7 @@ constexpr auto compile_format_string(S fmt) {
 }
 
 template <typename... Args, typename S,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
 constexpr auto compile(S fmt) {
   constexpr auto str = basic_string_view<typename S::char_type>(fmt);
   if constexpr (str.size() == 0) {
@@ -423,27 +456,28 @@ FMT_BEGIN_EXPORT
 
 #if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 
-template <typename CompiledFormat, typename... Args,
+template <typename CompiledFormat, typename... T,
           typename Char = typename CompiledFormat::char_type,
           FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
-FMT_INLINE std::basic_string<Char> format(const CompiledFormat& cf,
-                                          const Args&... args) {
+FMT_INLINE FMT_CONSTEXPR_STRING auto format(const CompiledFormat& cf,
+                                            const T&... args)
+    -> std::basic_string<Char> {
   auto s = std::basic_string<Char>();
   cf.format(std::back_inserter(s), args...);
   return s;
 }
 
-template <typename OutputIt, typename CompiledFormat, typename... Args,
+template <typename OutputIt, typename CompiledFormat, typename... T,
           FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
-constexpr FMT_INLINE OutputIt format_to(OutputIt out, const CompiledFormat& cf,
-                                        const Args&... args) {
+constexpr FMT_INLINE auto format_to(OutputIt out, const CompiledFormat& cf,
+                                    const T&... args) -> OutputIt {
   return cf.format(out, args...);
 }
 
-template <typename S, typename... Args,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
-FMT_INLINE std::basic_string<typename S::char_type> format(const S&,
-                                                           Args&&... args) {
+template <typename S, typename... T,
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
+FMT_INLINE FMT_CONSTEXPR_STRING auto format(const S&, T&&... args)
+    -> std::basic_string<typename S::char_type> {
   if constexpr (std::is_same<typename S::char_type, char>::value) {
     constexpr auto str = basic_string_view<typename S::char_type>(S());
     if constexpr (str.size() == 2 && str[0] == '{' && str[1] == '}') {
@@ -456,72 +490,97 @@ FMT_INLINE std::basic_string<typename S::char_type> format(const S&,
       }
     }
   }
-  constexpr auto compiled = detail::compile<Args...>(S());
+  constexpr auto compiled = detail::compile<T...>(S());
   if constexpr (std::is_same<remove_cvref_t<decltype(compiled)>,
                              detail::unknown_format>()) {
     return fmt::format(
         static_cast<basic_string_view<typename S::char_type>>(S()),
-        std::forward<Args>(args)...);
+        std::forward<T>(args)...);
   } else {
-    return fmt::format(compiled, std::forward<Args>(args)...);
+    return fmt::format(compiled, std::forward<T>(args)...);
   }
 }
 
-template <typename OutputIt, typename S, typename... Args,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
-FMT_CONSTEXPR OutputIt format_to(OutputIt out, const S&, Args&&... args) {
-  constexpr auto compiled = detail::compile<Args...>(S());
+template <typename OutputIt, typename S, typename... T,
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
+FMT_CONSTEXPR auto format_to(OutputIt out, const S&, T&&... args) -> OutputIt {
+  constexpr auto compiled = detail::compile<T...>(S());
   if constexpr (std::is_same<remove_cvref_t<decltype(compiled)>,
                              detail::unknown_format>()) {
     return fmt::format_to(
         out, static_cast<basic_string_view<typename S::char_type>>(S()),
-        std::forward<Args>(args)...);
+        std::forward<T>(args)...);
   } else {
-    return fmt::format_to(out, compiled, std::forward<Args>(args)...);
+    return fmt::format_to(out, compiled, std::forward<T>(args)...);
   }
 }
 #endif
 
-template <typename OutputIt, typename S, typename... Args,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
-auto format_to_n(OutputIt out, size_t n, const S& fmt, Args&&... args)
+template <typename OutputIt, typename S, typename... T,
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
+auto format_to_n(OutputIt out, size_t n, const S& fmt, T&&... args)
     -> format_to_n_result<OutputIt> {
   using traits = detail::fixed_buffer_traits;
   auto buf = detail::iterator_buffer<OutputIt, char, traits>(out, n);
-  fmt::format_to(std::back_inserter(buf), fmt, std::forward<Args>(args)...);
+  fmt::format_to(std::back_inserter(buf), fmt, std::forward<T>(args)...);
   return {buf.out(), buf.count()};
 }
 
-template <typename S, typename... Args,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
-FMT_CONSTEXPR20 auto formatted_size(const S& fmt, const Args&... args)
-    -> size_t {
-  return fmt::format_to(detail::counting_iterator(), fmt, args...).count();
+template <typename S, typename... T,
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
+FMT_CONSTEXPR20 auto formatted_size(const S& fmt, T&&... args) -> size_t {
+  auto buf = detail::counting_buffer<>();
+  fmt::format_to(appender(buf), fmt, std::forward<T>(args)...);
+  return buf.count();
 }
 
-template <typename S, typename... Args,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
-void print(std::FILE* f, const S& fmt, const Args&... args) {
-  memory_buffer buffer;
-  fmt::format_to(std::back_inserter(buffer), fmt, args...);
-  detail::print(f, {buffer.data(), buffer.size()});
+template <typename S, typename... T,
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
+void print(std::FILE* f, const S& fmt, T&&... args) {
+  auto buf = memory_buffer();
+  fmt::format_to(appender(buf), fmt, std::forward<T>(args)...);
+  detail::print(f, {buf.data(), buf.size()});
 }
 
-template <typename S, typename... Args,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
-void print(const S& fmt, const Args&... args) {
-  print(stdout, fmt, args...);
+template <typename S, typename... T,
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
+void print(const S& fmt, T&&... args) {
+  print(stdout, fmt, std::forward<T>(args)...);
 }
 
-#if FMT_USE_NONTYPE_TEMPLATE_ARGS
-inline namespace literals {
-template <detail_exported::fixed_string Str> constexpr auto operator""_cf() {
-  using char_t = remove_cvref_t<decltype(Str.data[0])>;
-  return detail::udl_compiled_string<char_t, sizeof(Str.data) / sizeof(char_t),
-                                     Str>();
-}
-}  // namespace literals
-#endif
+template <size_t N> class static_format_result {
+ private:
+  char data[N];
+
+ public:
+  template <typename S, typename... T,
+            FMT_ENABLE_IF(is_compiled_string<S>::value)>
+  explicit FMT_CONSTEXPR static_format_result(const S& fmt, T&&... args) {
+    *fmt::format_to(data, fmt, std::forward<T>(args)...) = '\0';
+  }
+
+  auto str() const -> fmt::string_view { return {data, N - 1}; }
+  auto c_str() const -> const char* { return data; }
+};
+
+/**
+ * Formats arguments according to the format string `fmt_str` and produces
+ * a string of the exact required size at compile time. Both the format string
+ * and the arguments must be compile-time expressions.
+ *
+ * The resulting string can be accessed as a C string via `c_str()` or as
+ * a `fmt::string_view` via `str()`.
+ *
+ * **Example**:
+ *
+ *     // Produces the static string "42" at compile time.
+ *     static constexpr auto result = FMT_STATIC_FORMAT("{}", 42);
+ *     const char* s = result.c_str();
+ */
+#define FMT_STATIC_FORMAT(fmt_str, ...)                            \
+  fmt::static_format_result<                                       \
+      fmt::formatted_size(FMT_COMPILE(fmt_str), __VA_ARGS__) + 1>( \
+      FMT_COMPILE(fmt_str), __VA_ARGS__)
 
 FMT_END_EXPORT
 FMT_END_NAMESPACE
diff --git a/contrib/fmt/include/fmt/format-inl.h b/contrib/fmt/include/fmt/format-inl.h
index 8d07cc6723..945cb912a6 100644
--- a/contrib/fmt/include/fmt/format-inl.h
+++ b/contrib/fmt/include/fmt/format-inl.h
@@ -14,10 +14,6 @@
 #  include <climits>
 #  include <cmath>
 #  include <exception>
-
-#  if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
-#    include <locale>
-#  endif
 #endif
 
 #if defined(_WIN32) && !defined(FMT_USE_WRITE_CONSOLE)
@@ -26,18 +22,54 @@
 
 #include "format.h"
 
+#if FMT_USE_LOCALE && !defined(FMT_MODULE)
+#  include <locale>
+#endif
+
+#ifndef FMT_FUNC
+#  define FMT_FUNC
+#endif
+
 FMT_BEGIN_NAMESPACE
-namespace detail {
 
+#ifndef FMT_CUSTOM_ASSERT_FAIL
 FMT_FUNC void assert_fail(const char* file, int line, const char* message) {
   // Use unchecked std::fprintf to avoid triggering another assertion when
-  // writing to stderr fails
+  // writing to stderr fails.
   std::fprintf(stderr, "%s:%d: assertion failed: %s", file, line, message);
-  // Chosen instead of std::abort to satisfy Clang in CUDA mode during device
-  // code pass.
-  std::terminate();
+  abort();
+}
+#endif
+
+#if FMT_USE_LOCALE
+namespace detail {
+using std::locale;
+using std::numpunct;
+using std::use_facet;
+}  // namespace detail
+#else
+namespace detail {
+struct locale {};
+template <typename Char> struct numpunct {
+  auto grouping() const -> std::string { return "\03"; }
+  auto thousands_sep() const -> Char { return ','; }
+  auto decimal_point() const -> Char { return '.'; }
+};
+template <typename Facet> Facet use_facet(locale) { return {}; }
+}  // namespace detail
+#endif  // FMT_USE_LOCALE
+
+template <typename Locale> auto locale_ref::get() const -> Locale {
+  using namespace detail;
+  static_assert(std::is_same<Locale, locale>::value, "");
+#if FMT_USE_LOCALE
+  if (locale_) return *static_cast<const locale*>(locale_);
+#endif
+  return locale();
 }
 
+namespace detail {
+
 FMT_FUNC void format_error_code(detail::buffer<char>& out, int error_code,
                                 string_view message) noexcept {
   // Report error code making sure that the output fits into
@@ -61,86 +93,67 @@ FMT_FUNC void format_error_code(detail::buffer<char>& out, int error_code,
   FMT_ASSERT(out.size() <= inline_buffer_size, "");
 }
 
-FMT_FUNC void report_error(format_func func, int error_code,
-                           const char* message) noexcept {
+FMT_FUNC void do_report_error(format_func func, int error_code,
+                              const char* message) noexcept {
   memory_buffer full_message;
   func(full_message, error_code, message);
-  // Don't use fwrite_fully because the latter may throw.
+  // Don't use fwrite_all because the latter may throw.
   if (std::fwrite(full_message.data(), full_message.size(), 1, stderr) > 0)
     std::fputc('\n', stderr);
 }
 
 // A wrapper around fwrite that throws on error.
-inline void fwrite_fully(const void* ptr, size_t count, FILE* stream) {
+inline void fwrite_all(const void* ptr, size_t count, FILE* stream) {
   size_t written = std::fwrite(ptr, 1, count, stream);
   if (written < count)
     FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
 }
 
-#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
-template <typename Locale>
-locale_ref::locale_ref(const Locale& loc) : locale_(&loc) {
-  static_assert(std::is_same<Locale, std::locale>::value, "");
-}
-
-template <typename Locale> auto locale_ref::get() const -> Locale {
-  static_assert(std::is_same<Locale, std::locale>::value, "");
-  return locale_ ? *static_cast<const std::locale*>(locale_) : std::locale();
-}
-
 template <typename Char>
 FMT_FUNC auto thousands_sep_impl(locale_ref loc) -> thousands_sep_result<Char> {
-  auto& facet = std::use_facet<std::numpunct<Char>>(loc.get<std::locale>());
+  auto&& facet = use_facet<numpunct<Char>>(loc.get<locale>());
   auto grouping = facet.grouping();
   auto thousands_sep = grouping.empty() ? Char() : facet.thousands_sep();
   return {std::move(grouping), thousands_sep};
 }
 template <typename Char>
 FMT_FUNC auto decimal_point_impl(locale_ref loc) -> Char {
-  return std::use_facet<std::numpunct<Char>>(loc.get<std::locale>())
-      .decimal_point();
+  return use_facet<numpunct<Char>>(loc.get<locale>()).decimal_point();
 }
-#else
-template <typename Char>
-FMT_FUNC auto thousands_sep_impl(locale_ref) -> thousands_sep_result<Char> {
-  return {"\03", FMT_STATIC_THOUSANDS_SEPARATOR};
-}
-template <typename Char> FMT_FUNC Char decimal_point_impl(locale_ref) {
-  return '.';
-}
-#endif
 
+#if FMT_USE_LOCALE
 FMT_FUNC auto write_loc(appender out, loc_value value,
                         const format_specs& specs, locale_ref loc) -> bool {
-#ifdef FMT_STATIC_THOUSANDS_SEPARATOR
-  value.visit(loc_writer<>{
-      out, specs, std::string(1, FMT_STATIC_THOUSANDS_SEPARATOR), "\3", "."});
-  return true;
-#else
   auto locale = loc.get<std::locale>();
   // We cannot use the num_put<char> facet because it may produce output in
   // a wrong encoding.
   using facet = format_facet<std::locale>;
   if (std::has_facet<facet>(locale))
-    return std::use_facet<facet>(locale).put(out, value, specs);
+    return use_facet<facet>(locale).put(out, value, specs);
   return facet(locale).put(out, value, specs);
-#endif
 }
+#endif
 }  // namespace detail
 
 FMT_FUNC void report_error(const char* message) {
+#if FMT_MSC_VERSION || defined(__NVCC__)
+  // Silence unreachable code warnings in MSVC and NVCC because these
+  // are nearly impossible to fix in a generic code.
+  volatile bool b = true;
+  if (!b) return;
+#endif
   FMT_THROW(format_error(message));
 }
 
 template <typename Locale> typename Locale::id format_facet<Locale>::id;
 
-#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
 template <typename Locale> format_facet<Locale>::format_facet(Locale& loc) {
-  auto& numpunct = std::use_facet<std::numpunct<char>>(loc);
-  grouping_ = numpunct.grouping();
-  if (!grouping_.empty()) separator_ = std::string(1, numpunct.thousands_sep());
+  auto& np = detail::use_facet<detail::numpunct<char>>(loc);
+  grouping_ = np.grouping();
+  if (!grouping_.empty()) separator_ = std::string(1, np.thousands_sep());
 }
 
+#if FMT_USE_LOCALE
 template <>
 FMT_API FMT_FUNC auto format_facet<std::locale>::do_put(
     appender out, loc_value val, const format_specs& specs) const -> bool {
@@ -163,11 +176,11 @@ inline auto operator==(basic_fp<F> x, basic_fp<F> y) -> bool {
 }
 
 // Compilers should be able to optimize this into the ror instruction.
-FMT_CONSTEXPR inline auto rotr(uint32_t n, uint32_t r) noexcept -> uint32_t {
+FMT_INLINE auto rotr(uint32_t n, uint32_t r) noexcept -> uint32_t {
   r &= 31;
   return (n >> r) | (n << (32 - r));
 }
-FMT_CONSTEXPR inline auto rotr(uint64_t n, uint32_t r) noexcept -> uint64_t {
+FMT_INLINE auto rotr(uint64_t n, uint32_t r) noexcept -> uint64_t {
   r &= 63;
   return (n >> r) | (n << (64 - r));
 }
@@ -201,7 +214,7 @@ inline auto floor_log10_pow2_minus_log10_4_over_3(int e) noexcept -> int {
   return (e * 631305 - 261663) >> 21;
 }
 
-FMT_INLINE_VARIABLE constexpr struct {
+FMT_INLINE_VARIABLE constexpr struct div_small_pow10_infos_struct {
   uint32_t divisor;
   int shift_amount;
 } div_small_pow10_infos[] = {{10, 16}, {100, 16}};
@@ -264,7 +277,7 @@ template <> struct cache_accessor<float> {
   static auto get_cached_power(int k) noexcept -> uint64_t {
     FMT_ASSERT(k >= float_info<float>::min_k && k <= float_info<float>::max_k,
                "k is out of range");
-    static constexpr const uint64_t pow10_significands[] = {
+    static constexpr uint64_t pow10_significands[] = {
         0x81ceb32c4b43fcf5, 0xa2425ff75e14fc32, 0xcad2f7f5359a3b3f,
         0xfd87b5f28300ca0e, 0x9e74d1b791e07e49, 0xc612062576589ddb,
         0xf79687aed3eec552, 0x9abe14cd44753b53, 0xc16d9a0095928a28,
@@ -359,7 +372,7 @@ template <> struct cache_accessor<double> {
     FMT_ASSERT(k >= float_info<double>::min_k && k <= float_info<double>::max_k,
                "k is out of range");
 
-    static constexpr const uint128_fallback pow10_significands[] = {
+    static constexpr uint128_fallback pow10_significands[] = {
 #if FMT_USE_FULL_CACHE_DRAGONBOX
       {0xff77b1fcbebcdc4f, 0x25e8e89c13bb0f7b},
       {0x9faacf3df73609b1, 0x77b191618c54e9ad},
@@ -1026,7 +1039,7 @@ template <> struct cache_accessor<double> {
 #if FMT_USE_FULL_CACHE_DRAGONBOX
     return pow10_significands[k - float_info<double>::min_k];
 #else
-    static constexpr const uint64_t powers_of_5_64[] = {
+    static constexpr uint64_t powers_of_5_64[] = {
         0x0000000000000001, 0x0000000000000005, 0x0000000000000019,
         0x000000000000007d, 0x0000000000000271, 0x0000000000000c35,
         0x0000000000003d09, 0x000000000001312d, 0x000000000005f5e1,
@@ -1086,7 +1099,7 @@ template <> struct cache_accessor<double> {
     return {r.high(), r.low() == 0};
   }
 
-  static auto compute_delta(cache_entry_type const& cache, int beta) noexcept
+  static auto compute_delta(const cache_entry_type& cache, int beta) noexcept
       -> uint32_t {
     return static_cast<uint32_t>(cache.high() >> (64 - 1 - beta));
   }
@@ -1138,8 +1151,8 @@ auto is_left_endpoint_integer_shorter_interval(int exponent) noexcept -> bool {
          exponent <= case_shorter_interval_left_endpoint_upper_threshold;
 }
 
-// Remove trailing zeros from n and return the number of zeros removed (float)
-FMT_INLINE int remove_trailing_zeros(uint32_t& n, int s = 0) noexcept {
+// Remove trailing zeros from n and return the number of zeros removed (float).
+FMT_INLINE auto remove_trailing_zeros(uint32_t& n, int s = 0) noexcept -> int {
   FMT_ASSERT(n != 0, "");
   // Modular inverse of 5 (mod 2^32): (mod_inv_5 * 5) mod 2^32 = 1.
   constexpr uint32_t mod_inv_5 = 0xcccccccd;
@@ -1159,22 +1172,19 @@ FMT_INLINE int remove_trailing_zeros(uint32_t& n, int s = 0) noexcept {
   return s;
 }
 
-// Removes trailing zeros and returns the number of zeros removed (double)
-FMT_INLINE int remove_trailing_zeros(uint64_t& n) noexcept {
+// Removes trailing zeros and returns the number of zeros removed (double).
+FMT_INLINE auto remove_trailing_zeros(uint64_t& n) noexcept -> int {
   FMT_ASSERT(n != 0, "");
 
-  // This magic number is ceil(2^90 / 10^8).
-  constexpr uint64_t magic_number = 12379400392853802749ull;
-  auto nm = umul128(n, magic_number);
-
   // Is n is divisible by 10^8?
-  if ((nm.high() & ((1ull << (90 - 64)) - 1)) == 0 && nm.low() < magic_number) {
+  constexpr uint32_t ten_pow_8 = 100000000u;
+  if ((n % ten_pow_8) == 0) {
     // If yes, work with the quotient...
-    auto n32 = static_cast<uint32_t>(nm.high() >> (90 - 64));
+    auto n32 = static_cast<uint32_t>(n / ten_pow_8);
     // ... and use the 32 bit variant of the function
-    int s = remove_trailing_zeros(n32, 8);
+    int num_zeros = remove_trailing_zeros(n32, 8);
     n = n32;
-    return s;
+    return num_zeros;
   }
 
   // If n is not divisible by 10^8, work with n itself.
@@ -1199,7 +1209,7 @@ FMT_INLINE int remove_trailing_zeros(uint64_t& n) noexcept {
 
 // The main algorithm for shorter interval case
 template <typename T>
-FMT_INLINE decimal_fp<T> shorter_interval_case(int exponent) noexcept {
+FMT_INLINE auto shorter_interval_case(int exponent) noexcept -> decimal_fp<T> {
   decimal_fp<T> ret_value;
   // Compute k and beta
   const int minus_k = floor_log10_pow2_minus_log10_4_over_3(exponent);
@@ -1425,7 +1435,7 @@ FMT_FUNC void format_system_error(detail::buffer<char>& out, int error_code,
 
 FMT_FUNC void report_system_error(int error_code,
                                   const char* message) noexcept {
-  report_error(format_system_error, error_code, message);
+  do_report_error(format_system_error, error_code, message);
 }
 
 FMT_FUNC auto vformat(string_view fmt, format_args args) -> std::string {
@@ -1438,17 +1448,40 @@ FMT_FUNC auto vformat(string_view fmt, format_args args) -> std::string {
 
 namespace detail {
 
+FMT_FUNC void vformat_to(buffer<char>& buf, string_view fmt, format_args args,
+                         locale_ref loc) {
+  auto out = appender(buf);
+  if (fmt.size() == 2 && equal2(fmt.data(), "{}"))
+    return args.get(0).visit(default_arg_formatter<char>{out});
+  parse_format_string(fmt,
+                      format_handler<>{parse_context<>(fmt), {out, args, loc}});
+}
+
 template <typename T> struct span {
   T* data;
   size_t size;
 };
 
-#ifdef _WIN32
-inline void flockfile(FILE* f) { _lock_file(f); }
-inline void funlockfile(FILE* f) { _unlock_file(f); }
-inline int getc_unlocked(FILE* f) { return _fgetc_nolock(f); }
+template <typename F> auto flockfile(F* f) -> decltype(_lock_file(f)) {
+  _lock_file(f);
+}
+template <typename F> auto funlockfile(F* f) -> decltype(_unlock_file(f)) {
+  _unlock_file(f);
+}
+
+#ifndef getc_unlocked
+template <typename F> auto getc_unlocked(F* f) -> decltype(_fgetc_nolock(f)) {
+  return _fgetc_nolock(f);
+}
 #endif
 
+template <typename F = FILE, typename Enable = void>
+struct has_flockfile : std::false_type {};
+
+template <typename F>
+struct has_flockfile<F, void_t<decltype(flockfile(&std::declval<F&>()))>>
+    : std::true_type {};
+
 // A FILE wrapper. F is FILE defined as a template parameter to make system API
 // detection work.
 template <typename F> class file_base {
@@ -1492,7 +1525,7 @@ template <typename F> class glibc_file : public file_base<F> {
   }
 
   void init_buffer() {
-    if (this->file_->_IO_write_ptr) return;
+    if (this->file_->_IO_write_ptr < this->file_->_IO_write_end) return;
     // Force buffer initialization by placing and removing a char in a buffer.
     putc_unlocked(0, this->file_);
     --this->file_->_IO_write_ptr;
@@ -1512,10 +1545,11 @@ template <typename F> class glibc_file : public file_base<F> {
 
   void advance_write_buffer(size_t size) { this->file_->_IO_write_ptr += size; }
 
-  bool needs_flush() const {
+  auto needs_flush() const -> bool {
     if ((this->file_->_flags & line_buffered) == 0) return false;
     char* end = this->file_->_IO_write_end;
-    return memchr(end, '\n', to_unsigned(this->file_->_IO_write_ptr - end));
+    auto size = max_of<ptrdiff_t>(this->file_->_IO_write_ptr - end, 0);
+    return memchr(end, '\n', static_cast<size_t>(size));
   }
 
   void flush() { fflush_unlocked(this->file_); }
@@ -1539,7 +1573,7 @@ template <typename F> class apple_file : public file_base<F> {
   void init_buffer() {
     if (this->file_->_p) return;
     // Force buffer initialization by placing and removing a char in a buffer.
-    putc_unlocked(0, this->file_);
+    if (!FMT_CLANG_ANALYZER) putc_unlocked(0, this->file_);
     --this->file_->_p;
     ++this->file_->_w;
   }
@@ -1560,7 +1594,7 @@ template <typename F> class apple_file : public file_base<F> {
     this->file_->_w -= size;
   }
 
-  bool needs_flush() const {
+  auto needs_flush() const -> bool {
     if ((this->file_->_flags & line_buffered) == 0) return false;
     return memchr(this->file_->_p + this->file_->_w, '\n',
                   to_unsigned(-this->file_->_w));
@@ -1601,7 +1635,7 @@ template <typename F> class fallback_file : public file_base<F> {
 };
 
 #ifndef FMT_USE_FALLBACK_FILE
-#  define FMT_USE_FALLBACK_FILE 1
+#  define FMT_USE_FALLBACK_FILE 0
 #endif
 
 template <typename F,
@@ -1619,7 +1653,15 @@ inline auto get_file(FILE* f, ...) -> fallback_file<FILE> { return f; }
 
 using file_ref = decltype(get_file(static_cast<FILE*>(nullptr), 0));
 
+template <typename F = FILE, typename Enable = void>
 class file_print_buffer : public buffer<char> {
+ public:
+  explicit file_print_buffer(F*) : buffer(nullptr, size_t()) {}
+};
+
+template <typename F>
+class file_print_buffer<F, enable_if_t<has_flockfile<F>::value>>
+    : public buffer<char> {
  private:
   file_ref file_;
 
@@ -1634,7 +1676,7 @@ class file_print_buffer : public buffer<char> {
   }
 
  public:
-  explicit file_print_buffer(FILE* f) : buffer(grow, size_t()), file_(f) {
+  explicit file_print_buffer(F* f) : buffer(grow, size_t()), file_(f) {
     flockfile(f);
     file_.init_buffer();
     auto buf = file_.get_write_buffer();
@@ -1643,7 +1685,8 @@ class file_print_buffer : public buffer<char> {
   ~file_print_buffer() {
     file_.advance_write_buffer(size());
     bool flush = file_.needs_flush();
-    funlockfile(file_);
+    F* f = file_;    // Make funlockfile depend on the template parameter F
+    funlockfile(f);  // for the system API detection to work.
     if (flush) fflush(file_);
   }
 };
@@ -1669,7 +1712,7 @@ FMT_FUNC void vprint_mojibake(std::FILE* f, string_view fmt, format_args args,
   auto buffer = memory_buffer();
   detail::vformat_to(buffer, fmt, args);
   if (newline) buffer.push_back('\n');
-  fwrite_fully(buffer.data(), buffer.size(), f);
+  fwrite_all(buffer.data(), buffer.size(), f);
 }
 #endif
 
@@ -1681,7 +1724,7 @@ FMT_FUNC void print(std::FILE* f, string_view text) {
     if (write_console(fd, text)) return;
   }
 #endif
-  fwrite_fully(text.data(), text.size(), f);
+  fwrite_all(text.data(), text.size(), f);
 }
 }  // namespace detail
 
@@ -1692,8 +1735,9 @@ FMT_FUNC void vprint_buffered(std::FILE* f, string_view fmt, format_args args) {
 }
 
 FMT_FUNC void vprint(std::FILE* f, string_view fmt, format_args args) {
-  if (!detail::file_ref(f).is_buffered()) return vprint_buffered(f, fmt, args);
-  auto&& buffer = detail::file_print_buffer(f);
+  if (!detail::file_ref(f).is_buffered() || !detail::has_flockfile<>())
+    return vprint_buffered(f, fmt, args);
+  auto&& buffer = detail::file_print_buffer<>(f);
   return detail::vformat_to(buffer, fmt, args);
 }
 
diff --git a/contrib/fmt/include/fmt/format.h b/contrib/fmt/include/fmt/format.h
index 7c2a19b408..4a6530072f 100644
--- a/contrib/fmt/include/fmt/format.h
+++ b/contrib/fmt/include/fmt/format.h
@@ -40,12 +40,21 @@
 
 #include "base.h"
 
+// libc++ supports string_view in pre-c++17.
+#if FMT_HAS_INCLUDE(<string_view>) && \
+    (FMT_CPLUSPLUS >= 201703L || defined(_LIBCPP_VERSION))
+#  define FMT_USE_STRING_VIEW
+#endif
+
 #ifndef FMT_MODULE
-#  include <cmath>             // std::signbit
-#  include <cstdint>           // uint32_t
-#  include <cstring>           // std::memcpy
-#  include <initializer_list>  // std::initializer_list
-#  include <limits>            // std::numeric_limits
+#  include <stdlib.h>  // malloc, free
+
+#  include <cmath>    // std::signbit
+#  include <cstddef>  // std::byte
+#  include <cstdint>  // uint32_t
+#  include <cstring>  // std::memcpy
+#  include <limits>   // std::numeric_limits
+#  include <new>      // std::bad_alloc
 #  if defined(__GLIBCXX__) && !defined(_GLIBCXX_USE_DUAL_ABI)
 // Workaround for pre gcc 5 libstdc++.
 #    include <memory>  // std::allocator_traits
@@ -54,37 +63,50 @@
 #  include <string>        // std::string
 #  include <system_error>  // std::system_error
 
-// Checking FMT_CPLUSPLUS for warning suppression in MSVC.
+// Check FMT_CPLUSPLUS to avoid a warning in MSVC.
 #  if FMT_HAS_INCLUDE(<bit>) && FMT_CPLUSPLUS > 201703L
 #    include <bit>  // std::bit_cast
 #  endif
 
-// libc++ supports string_view in pre-c++17.
-#  if FMT_HAS_INCLUDE(<string_view>) && \
-      (FMT_CPLUSPLUS >= 201703L || defined(_LIBCPP_VERSION))
+#  if defined(FMT_USE_STRING_VIEW)
 #    include <string_view>
-#    define FMT_USE_STRING_VIEW
+#  endif
+
+#  if FMT_MSC_VERSION
+#    include <intrin.h>  // _BitScanReverse[64], _umul128
 #  endif
 #endif  // FMT_MODULE
 
+#if defined(FMT_USE_NONTYPE_TEMPLATE_ARGS)
+// Use the provided definition.
+#elif defined(__NVCOMPILER)
+#  define FMT_USE_NONTYPE_TEMPLATE_ARGS 0
+#elif FMT_GCC_VERSION >= 903 && FMT_CPLUSPLUS >= 201709L
+#  define FMT_USE_NONTYPE_TEMPLATE_ARGS 1
+#elif defined(__cpp_nontype_template_args) && \
+    __cpp_nontype_template_args >= 201911L
+#  define FMT_USE_NONTYPE_TEMPLATE_ARGS 1
+#elif FMT_CLANG_VERSION >= 1200 && FMT_CPLUSPLUS >= 202002L
+#  define FMT_USE_NONTYPE_TEMPLATE_ARGS 1
+#else
+#  define FMT_USE_NONTYPE_TEMPLATE_ARGS 0
+#endif
+
 #if defined __cpp_inline_variables && __cpp_inline_variables >= 201606L
 #  define FMT_INLINE_VARIABLE inline
 #else
 #  define FMT_INLINE_VARIABLE
 #endif
 
-#ifndef FMT_NO_UNIQUE_ADDRESS
-#  if FMT_CPLUSPLUS >= 202002L
-#    if FMT_HAS_CPP_ATTRIBUTE(no_unique_address)
-#      define FMT_NO_UNIQUE_ADDRESS [[no_unique_address]]
-// VS2019 v16.10 and later except clang-cl (https://reviews.llvm.org/D110485).
-#    elif (FMT_MSC_VERSION >= 1929) && !FMT_CLANG_VERSION
-#      define FMT_NO_UNIQUE_ADDRESS [[msvc::no_unique_address]]
-#    endif
-#  endif
-#endif
-#ifndef FMT_NO_UNIQUE_ADDRESS
-#  define FMT_NO_UNIQUE_ADDRESS
+// Check if RTTI is disabled.
+#ifdef FMT_USE_RTTI
+// Use the provided definition.
+#elif defined(__GXX_RTTI) || FMT_HAS_FEATURE(cxx_rtti) || defined(_CPPRTTI) || \
+    defined(__INTEL_RTTI__) || defined(__RTTI)
+// __RTTI is for EDG compilers. _CPPRTTI is for MSVC.
+#  define FMT_USE_RTTI 1
+#else
+#  define FMT_USE_RTTI 0
 #endif
 
 // Visibility when compiled as a shared library/object.
@@ -94,61 +116,71 @@
 #  define FMT_SO_VISIBILITY(value)
 #endif
 
-#ifdef __has_builtin
-#  define FMT_HAS_BUILTIN(x) __has_builtin(x)
-#else
-#  define FMT_HAS_BUILTIN(x) 0
-#endif
-
 #if FMT_GCC_VERSION || FMT_CLANG_VERSION
 #  define FMT_NOINLINE __attribute__((noinline))
 #else
 #  define FMT_NOINLINE
 #endif
 
-#ifndef FMT_THROW
-#  if FMT_EXCEPTIONS
-#    if FMT_MSC_VERSION || defined(__NVCC__)
-FMT_BEGIN_NAMESPACE
-namespace detail {
-template <typename Exception> inline void do_throw(const Exception& x) {
-  // Silence unreachable code warnings in MSVC and NVCC because these
-  // are nearly impossible to fix in a generic code.
-  volatile bool b = true;
-  if (b) throw x;
-}
-}  // namespace detail
-FMT_END_NAMESPACE
-#      define FMT_THROW(x) detail::do_throw(x)
+#ifdef FMT_DEPRECATED
+// Use the provided definition.
+#elif FMT_HAS_CPP14_ATTRIBUTE(deprecated)
+#  define FMT_DEPRECATED [[deprecated]]
+#else
+#  define FMT_DEPRECATED /* deprecated */
+#endif
+
+// Detect constexpr std::string.
+#if !FMT_USE_CONSTEVAL
+#  define FMT_USE_CONSTEXPR_STRING 0
+#elif defined(__cpp_lib_constexpr_string) && \
+    __cpp_lib_constexpr_string >= 201907L
+#  if FMT_CLANG_VERSION && FMT_GLIBCXX_RELEASE
+// clang + libstdc++ are able to work only starting with gcc13.3
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113294
+#    if FMT_GLIBCXX_RELEASE < 13
+#      define FMT_USE_CONSTEXPR_STRING 0
+#    elif FMT_GLIBCXX_RELEASE == 13 && __GLIBCXX__ < 20240521
+#      define FMT_USE_CONSTEXPR_STRING 0
 #    else
-#      define FMT_THROW(x) throw x
+#      define FMT_USE_CONSTEXPR_STRING 1
 #    endif
 #  else
-#    define FMT_THROW(x) \
-      ::fmt::detail::assert_fail(__FILE__, __LINE__, (x).what())
+#    define FMT_USE_CONSTEXPR_STRING 1
 #  endif
+#else
+#  define FMT_USE_CONSTEXPR_STRING 0
+#endif
+#if FMT_USE_CONSTEXPR_STRING
+#  define FMT_CONSTEXPR_STRING constexpr
+#else
+#  define FMT_CONSTEXPR_STRING
 #endif
 
-#ifndef FMT_MAYBE_UNUSED
-#  if FMT_HAS_CPP17_ATTRIBUTE(maybe_unused)
-#    define FMT_MAYBE_UNUSED [[maybe_unused]]
-#  else
-#    define FMT_MAYBE_UNUSED
-#  endif
+// GCC 4.9 doesn't support qualified names in specializations.
+namespace std {
+template <typename T> struct iterator_traits<fmt::basic_appender<T>> {
+  using iterator_category = output_iterator_tag;
+  using value_type = T;
+  using difference_type =
+      decltype(static_cast<int*>(nullptr) - static_cast<int*>(nullptr));
+  using pointer = void;
+  using reference = void;
+};
+}  // namespace std
+
+#ifdef FMT_THROW
+// Use the provided definition.
+#elif FMT_USE_EXCEPTIONS
+#  define FMT_THROW(x) throw x
+#else
+#  define FMT_THROW(x) ::fmt::assert_fail(__FILE__, __LINE__, (x).what())
 #endif
 
-#ifndef FMT_USE_USER_DEFINED_LITERALS
-// EDG based compilers (Intel, NVIDIA, Elbrus, etc), GCC and MSVC support UDLs.
-//
-// GCC before 4.9 requires a space in `operator"" _a` which is invalid in later
-// compiler versions.
-#  if (FMT_HAS_FEATURE(cxx_user_literals) || FMT_GCC_VERSION >= 409 || \
-       FMT_MSC_VERSION >= 1900) &&                                     \
-      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= /* UDL feature */ 480)
-#    define FMT_USE_USER_DEFINED_LITERALS 1
-#  else
-#    define FMT_USE_USER_DEFINED_LITERALS 0
-#  endif
+#ifdef __clang_analyzer__
+#  define FMT_CLANG_ANALYZER 1
+#else
+#  define FMT_CLANG_ANALYZER 0
 #endif
 
 // Defining FMT_REDUCE_INT_INSTANTIATIONS to 1, will reduce the number of
@@ -159,7 +191,15 @@ FMT_END_NAMESPACE
 #  define FMT_REDUCE_INT_INSTANTIATIONS 0
 #endif
 
-// __builtin_clz is broken in clang with Microsoft CodeGen:
+FMT_BEGIN_NAMESPACE
+
+template <typename Char, typename Traits, typename Allocator>
+struct is_contiguous<std::basic_string<Char, Traits, Allocator>>
+    : std::true_type {};
+
+namespace detail {
+
+// __builtin_clz is broken in clang with Microsoft codegen:
 // https://github.com/fmtlib/fmt/issues/519.
 #if !FMT_MSC_VERSION
 #  if FMT_HAS_BUILTIN(__builtin_clz) || FMT_GCC_VERSION || FMT_ICC_VERSION
@@ -170,53 +210,30 @@ FMT_END_NAMESPACE
 #  endif
 #endif
 
-// __builtin_ctz is broken in Intel Compiler Classic on Windows:
-// https://github.com/fmtlib/fmt/issues/2510.
-#ifndef __ICL
-#  if FMT_HAS_BUILTIN(__builtin_ctz) || FMT_GCC_VERSION || FMT_ICC_VERSION || \
-      defined(__NVCOMPILER)
-#    define FMT_BUILTIN_CTZ(n) __builtin_ctz(n)
-#  endif
-#  if FMT_HAS_BUILTIN(__builtin_ctzll) || FMT_GCC_VERSION || \
-      FMT_ICC_VERSION || defined(__NVCOMPILER)
-#    define FMT_BUILTIN_CTZLL(n) __builtin_ctzll(n)
-#  endif
-#endif
-
-#if FMT_MSC_VERSION
-#  include <intrin.h>  // _BitScanReverse[64], _BitScanForward[64], _umul128
-#endif
-
-// Some compilers masquerade as both MSVC and GCC-likes or otherwise support
+// Some compilers masquerade as both MSVC and GCC but otherwise support
 // __builtin_clz and __builtin_clzll, so only define FMT_BUILTIN_CLZ using the
 // MSVC intrinsics if the clz and clzll builtins are not available.
-#if FMT_MSC_VERSION && !defined(FMT_BUILTIN_CLZLL) && \
-    !defined(FMT_BUILTIN_CTZLL)
-FMT_BEGIN_NAMESPACE
-namespace detail {
+#if FMT_MSC_VERSION && !defined(FMT_BUILTIN_CLZLL)
 // Avoid Clang with Microsoft CodeGen's -Wunknown-pragmas warning.
-#  if !defined(__clang__)
-#    pragma intrinsic(_BitScanForward)
+#  ifndef __clang__
 #    pragma intrinsic(_BitScanReverse)
-#    if defined(_WIN64)
-#      pragma intrinsic(_BitScanForward64)
+#    ifdef _WIN64
 #      pragma intrinsic(_BitScanReverse64)
 #    endif
 #  endif
 
 inline auto clz(uint32_t x) -> int {
+  FMT_ASSERT(x != 0, "");
+  FMT_MSC_WARNING(suppress : 6102)  // Suppress a bogus static analysis warning.
   unsigned long r = 0;
   _BitScanReverse(&r, x);
-  FMT_ASSERT(x != 0, "");
-  // Static analysis complains about using uninitialized data
-  // "r", but the only way that can happen is if "x" is 0,
-  // which the callers guarantee to not happen.
-  FMT_MSC_WARNING(suppress : 6102)
   return 31 ^ static_cast<int>(r);
 }
 #  define FMT_BUILTIN_CLZ(n) detail::clz(n)
 
 inline auto clzll(uint64_t x) -> int {
+  FMT_ASSERT(x != 0, "");
+  FMT_MSC_WARNING(suppress : 6102)  // Suppress a bogus static analysis warning.
   unsigned long r = 0;
 #  ifdef _WIN64
   _BitScanReverse64(&r, x);
@@ -227,48 +244,10 @@ inline auto clzll(uint64_t x) -> int {
   // Scan the low 32 bits.
   _BitScanReverse(&r, static_cast<uint32_t>(x));
 #  endif
-  FMT_ASSERT(x != 0, "");
-  FMT_MSC_WARNING(suppress : 6102)  // Suppress a bogus static analysis warning.
   return 63 ^ static_cast<int>(r);
 }
 #  define FMT_BUILTIN_CLZLL(n) detail::clzll(n)
-
-inline auto ctz(uint32_t x) -> int {
-  unsigned long r = 0;
-  _BitScanForward(&r, x);
-  FMT_ASSERT(x != 0, "");
-  FMT_MSC_WARNING(suppress : 6102)  // Suppress a bogus static analysis warning.
-  return static_cast<int>(r);
-}
-#  define FMT_BUILTIN_CTZ(n) detail::ctz(n)
-
-inline auto ctzll(uint64_t x) -> int {
-  unsigned long r = 0;
-  FMT_ASSERT(x != 0, "");
-  FMT_MSC_WARNING(suppress : 6102)  // Suppress a bogus static analysis warning.
-#  ifdef _WIN64
-  _BitScanForward64(&r, x);
-#  else
-  // Scan the low 32 bits.
-  if (_BitScanForward(&r, static_cast<uint32_t>(x))) return static_cast<int>(r);
-  // Scan the high 32 bits.
-  _BitScanForward(&r, static_cast<uint32_t>(x >> 32));
-  r += 32;
-#  endif
-  return static_cast<int>(r);
-}
-#  define FMT_BUILTIN_CTZLL(n) detail::ctzll(n)
-}  // namespace detail
-FMT_END_NAMESPACE
-#endif
-
-FMT_BEGIN_NAMESPACE
-
-template <typename Char, typename Traits, typename Allocator>
-struct is_contiguous<std::basic_string<Char, Traits, Allocator>>
-    : std::true_type {};
-
-namespace detail {
+#endif  // FMT_MSC_VERSION && !defined(FMT_BUILTIN_CLZLL)
 
 FMT_CONSTEXPR inline void abort_fuzzing_if(bool condition) {
   ignore_unused(condition);
@@ -280,7 +259,20 @@ FMT_CONSTEXPR inline void abort_fuzzing_if(bool condition) {
 #if defined(FMT_USE_STRING_VIEW)
 template <typename Char> using std_string_view = std::basic_string_view<Char>;
 #else
-template <typename T> struct std_string_view {};
+template <typename Char> struct std_string_view {
+  operator basic_string_view<Char>() const;
+};
+#endif
+
+template <typename Char, Char... C> struct string_literal {
+  static constexpr Char value[sizeof...(C)] = {C...};
+  constexpr operator basic_string_view<Char>() const {
+    return {value, sizeof...(C)};
+  }
+};
+#if FMT_CPLUSPLUS < 201703L
+template <typename Char, Char... C>
+constexpr Char string_literal<Char, C...>::value[sizeof...(C)];
 #endif
 
 // Implementation of std::bit_cast for pre-C++20.
@@ -352,13 +344,14 @@ class uint128_fallback {
       -> uint128_fallback {
     return {~n.hi_, ~n.lo_};
   }
-  friend auto operator+(const uint128_fallback& lhs,
-                        const uint128_fallback& rhs) -> uint128_fallback {
+  friend FMT_CONSTEXPR auto operator+(const uint128_fallback& lhs,
+                                      const uint128_fallback& rhs)
+      -> uint128_fallback {
     auto result = uint128_fallback(lhs);
     result += rhs;
     return result;
   }
-  friend auto operator*(const uint128_fallback& lhs, uint32_t rhs)
+  friend FMT_CONSTEXPR auto operator*(const uint128_fallback& lhs, uint32_t rhs)
       -> uint128_fallback {
     FMT_ASSERT(lhs.hi_ == 0, "");
     uint64_t hi = (lhs.lo_ >> 32) * rhs;
@@ -366,7 +359,7 @@ class uint128_fallback {
     uint64_t new_lo = (hi << 32) + lo;
     return {(hi >> 32) + (new_lo < lo ? 1 : 0), new_lo};
   }
-  friend auto operator-(const uint128_fallback& lhs, uint64_t rhs)
+  friend constexpr auto operator-(const uint128_fallback& lhs, uint64_t rhs)
       -> uint128_fallback {
     return {lhs.hi_ - (lhs.lo_ < rhs ? 1 : 0), lhs.lo_ - rhs};
   }
@@ -446,17 +439,17 @@ template <> constexpr auto num_bits<uint128_fallback>() -> int { return 128; }
 // and 128-bit pointers to uint128_fallback.
 template <typename To, typename From, FMT_ENABLE_IF(sizeof(To) > sizeof(From))>
 inline auto bit_cast(const From& from) -> To {
-  constexpr auto size = static_cast<int>(sizeof(From) / sizeof(unsigned));
+  constexpr auto size = static_cast<int>(sizeof(From) / sizeof(unsigned short));
   struct data_t {
-    unsigned value[static_cast<unsigned>(size)];
+    unsigned short value[static_cast<unsigned>(size)];
   } data = bit_cast<data_t>(from);
   auto result = To();
   if (const_check(is_big_endian())) {
     for (int i = 0; i < size; ++i)
-      result = (result << num_bits<unsigned>()) | data.value[i];
+      result = (result << num_bits<unsigned short>()) | data.value[i];
   } else {
     for (int i = size - 1; i >= 0; --i)
-      result = (result << num_bits<unsigned>()) | data.value[i];
+      result = (result << num_bits<unsigned short>()) | data.value[i];
   }
   return result;
 }
@@ -492,21 +485,6 @@ FMT_INLINE void assume(bool condition) {
 #endif
 }
 
-// An approximation of iterator_t for pre-C++20 systems.
-template <typename T>
-using iterator_t = decltype(std::begin(std::declval<T&>()));
-template <typename T> using sentinel_t = decltype(std::end(std::declval<T&>()));
-
-// A workaround for std::string not having mutable data() until C++17.
-template <typename Char>
-inline auto get_data(std::basic_string<Char>& s) -> Char* {
-  return &s[0];
-}
-template <typename Container>
-inline auto get_data(Container& c) -> typename Container::value_type* {
-  return c.data();
-}
-
 // Attempts to reserve space for n extra characters in the output range.
 // Returns a pointer to the reserved range or a reference to it.
 template <typename OutputIt,
@@ -515,16 +493,17 @@ template <typename OutputIt,
 #if FMT_CLANG_VERSION >= 307 && !FMT_ICC_VERSION
 __attribute__((no_sanitize("undefined")))
 #endif
-inline auto
+FMT_CONSTEXPR20 inline auto
 reserve(OutputIt it, size_t n) -> typename OutputIt::value_type* {
   auto& c = get_container(it);
   size_t size = c.size();
   c.resize(size + n);
-  return get_data(c) + size;
+  return &c[size];
 }
 
 template <typename T>
-inline auto reserve(basic_appender<T> it, size_t n) -> basic_appender<T> {
+FMT_CONSTEXPR20 inline auto reserve(basic_appender<T> it, size_t n)
+    -> basic_appender<T> {
   buffer<T>& buf = get_container(it);
   buf.try_reserve(buf.size() + n);
   return it;
@@ -543,8 +522,15 @@ template <typename T, typename OutputIt>
 constexpr auto to_pointer(OutputIt, size_t) -> T* {
   return nullptr;
 }
-template <typename T> auto to_pointer(basic_appender<T> it, size_t n) -> T* {
+template <typename T> FMT_CONSTEXPR auto to_pointer(T*& ptr, size_t n) -> T* {
+  T* begin = ptr;
+  ptr += n;
+  return begin;
+}
+template <typename T>
+FMT_CONSTEXPR20 auto to_pointer(basic_appender<T> it, size_t n) -> T* {
   buffer<T>& buf = get_container(it);
+  buf.try_reserve(buf.size() + n);
   auto size = buf.size();
   if (buf.capacity() < size + n) return nullptr;
   buf.try_resize(size + n);
@@ -575,9 +561,9 @@ FMT_CONSTEXPR auto fill_n(OutputIt out, Size count, const T& value)
 }
 template <typename T, typename Size>
 FMT_CONSTEXPR20 auto fill_n(T* out, Size count, char value) -> T* {
-  if (is_constant_evaluated()) {
-    return fill_n<T*, Size, T>(out, count, value);
-  }
+  if (is_constant_evaluated()) return fill_n<T*, Size, T>(out, count, value);
+  static_assert(sizeof(T) == 1,
+                "sizeof(T) must be 1 to use char for initialization");
   std::memset(out, value, to_unsigned(count));
   return out + count;
 }
@@ -607,10 +593,10 @@ FMT_CONSTEXPR FMT_NOINLINE auto copy_noinline(InputIt begin, InputIt end,
  */
 FMT_CONSTEXPR inline auto utf8_decode(const char* s, uint32_t* c, int* e)
     -> const char* {
-  constexpr const int masks[] = {0x00, 0x7f, 0x1f, 0x0f, 0x07};
-  constexpr const uint32_t mins[] = {4194304, 0, 128, 2048, 65536};
-  constexpr const int shiftc[] = {0, 18, 12, 6, 0};
-  constexpr const int shifte[] = {0, 6, 4, 2, 0};
+  constexpr int masks[] = {0x00, 0x7f, 0x1f, 0x0f, 0x07};
+  constexpr uint32_t mins[] = {4194304, 0, 128, 2048, 65536};
+  constexpr int shiftc[] = {0, 18, 12, 6, 0};
+  constexpr int shifte[] = {0, 6, 4, 2, 0};
 
   int len = "\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\0\0\0\0\0\0\0\0\2\2\2\2\3\3\4"
       [static_cast<unsigned char>(*s) >> 3];
@@ -656,6 +642,7 @@ FMT_CONSTEXPR void for_each_codepoint(string_view s, F f) {
                     string_view(ptr, error ? 1 : to_unsigned(end - buf_ptr)));
     return result ? (error ? buf_ptr + 1 : end) : nullptr;
   };
+
   auto p = s.data();
   const size_t block_size = 4;  // utf8_decode always reads blocks of 4 chars.
   if (s.size() >= block_size) {
@@ -664,34 +651,25 @@ FMT_CONSTEXPR void for_each_codepoint(string_view s, F f) {
       if (!p) return;
     }
   }
-  if (auto num_chars_left = s.data() + s.size() - p) {
-    char buf[2 * block_size - 1] = {};
-    copy<char>(p, p + num_chars_left, buf);
-    const char* buf_ptr = buf;
-    do {
-      auto end = decode(buf_ptr, p);
-      if (!end) return;
-      p += end - buf_ptr;
-      buf_ptr = end;
-    } while (buf_ptr - buf < num_chars_left);
-  }
+  auto num_chars_left = to_unsigned(s.data() + s.size() - p);
+  if (num_chars_left == 0) return;
+
+  // Suppress bogus -Wstringop-overflow.
+  if (FMT_GCC_VERSION) num_chars_left &= 3;
+  char buf[2 * block_size - 1] = {};
+  copy<char>(p, p + num_chars_left, buf);
+  const char* buf_ptr = buf;
+  do {
+    auto end = decode(buf_ptr, p);
+    if (!end) return;
+    p += end - buf_ptr;
+    buf_ptr = end;
+  } while (buf_ptr < buf + num_chars_left);
 }
 
-template <typename Char>
-inline auto compute_width(basic_string_view<Char> s) -> size_t {
-  return s.size();
-}
-
-// Computes approximate display width of a UTF-8 string.
-FMT_CONSTEXPR inline auto compute_width(string_view s) -> size_t {
-  size_t num_code_points = 0;
-  // It is not a lambda for compatibility with C++14.
-  struct count_code_points {
-    size_t* count;
-    FMT_CONSTEXPR auto operator()(uint32_t cp, string_view) const -> bool {
-      *count += detail::to_unsigned(
-          1 +
-          (cp >= 0x1100 &&
+FMT_CONSTEXPR inline auto display_width_of(uint32_t cp) noexcept -> size_t {
+  return to_unsigned(
+      1 + (cp >= 0x1100 &&
            (cp <= 0x115f ||  // Hangul Jamo init. consonants
             cp == 0x2329 ||  // LEFT-POINTING ANGLE BRACKET
             cp == 0x232a ||  // RIGHT-POINTING ANGLE BRACKET
@@ -709,33 +687,6 @@ FMT_CONSTEXPR inline auto compute_width(string_view s) -> size_t {
             (cp >= 0x1f300 && cp <= 0x1f64f) ||
             // Supplemental Symbols and Pictographs:
             (cp >= 0x1f900 && cp <= 0x1f9ff))));
-      return true;
-    }
-  };
-  // We could avoid branches by using utf8_decode directly.
-  for_each_codepoint(s, count_code_points{&num_code_points});
-  return num_code_points;
-}
-
-template <typename Char>
-inline auto code_point_index(basic_string_view<Char> s, size_t n) -> size_t {
-  size_t size = s.size();
-  return n < size ? n : size;
-}
-
-// Calculates the index of the nth code point in a UTF-8 string.
-inline auto code_point_index(string_view s, size_t n) -> size_t {
-  size_t result = s.size();
-  const char* begin = s.begin();
-  for_each_codepoint(s, [begin, &n, &result](uint32_t, string_view sv) {
-    if (n != 0) {
-      --n;
-      return true;
-    }
-    result = to_unsigned(sv.begin() - begin);
-    return false;
-  });
-  return result;
 }
 
 template <typename T> struct is_integral : std::is_integral<T> {};
@@ -753,19 +704,9 @@ using is_integer =
                   !std::is_same<T, char>::value &&
                   !std::is_same<T, wchar_t>::value>;
 
-#ifndef FMT_USE_FLOAT
-#  define FMT_USE_FLOAT 1
-#endif
-#ifndef FMT_USE_DOUBLE
-#  define FMT_USE_DOUBLE 1
-#endif
-#ifndef FMT_USE_LONG_DOUBLE
-#  define FMT_USE_LONG_DOUBLE 1
-#endif
-
 #if defined(FMT_USE_FLOAT128)
 // Use the provided definition.
-#elif FMT_CLANG_VERSION && FMT_HAS_INCLUDE(<quadmath.h>)
+#elif FMT_CLANG_VERSION >= 309 && FMT_HAS_INCLUDE(<quadmath.h>)
 #  define FMT_USE_FLOAT128 1
 #elif FMT_GCC_VERSION && defined(_GLIBCXX_USE_FLOAT128) && \
     !defined(__STRICT_ANSI__)
@@ -776,20 +717,22 @@ using is_integer =
 #if FMT_USE_FLOAT128
 using float128 = __float128;
 #else
-using float128 = void;
+struct float128 {};
 #endif
 
 template <typename T> using is_float128 = std::is_same<T, float128>;
 
-template <typename T>
-using is_floating_point =
-    bool_constant<std::is_floating_point<T>::value || is_float128<T>::value>;
+template <typename T> struct is_floating_point : std::is_floating_point<T> {};
+template <> struct is_floating_point<float128> : std::true_type {};
 
-template <typename T, bool = std::is_floating_point<T>::value>
+template <typename T, bool = is_floating_point<T>::value>
 struct is_fast_float : bool_constant<std::numeric_limits<T>::is_iec559 &&
                                      sizeof(T) <= sizeof(double)> {};
 template <typename T> struct is_fast_float<T, false> : std::false_type {};
 
+template <typename T>
+using fast_float_t = conditional_t<sizeof(T) == sizeof(double), double, float>;
+
 template <typename T>
 using is_double_double = bool_constant<std::numeric_limits<T>::digits == 106>;
 
@@ -797,10 +740,37 @@ using is_double_double = bool_constant<std::numeric_limits<T>::digits == 106>;
 #  define FMT_USE_FULL_CACHE_DRAGONBOX 0
 #endif
 
-template <typename T, typename Enable = void>
-struct is_locale : std::false_type {};
-template <typename T>
-struct is_locale<T, void_t<decltype(T::classic())>> : std::true_type {};
+// An allocator that uses malloc/free to allow removing dependency on the C++
+// standard libary runtime. std::decay is used for back_inserter to be found by
+// ADL when applied to memory_buffer.
+template <typename T> struct allocator : private std::decay<void> {
+  using value_type = T;
+
+  auto allocate(size_t n) -> T* {
+    FMT_ASSERT(n <= max_value<size_t>() / sizeof(T), "");
+    T* p = static_cast<T*>(malloc(n * sizeof(T)));
+    if (!p) FMT_THROW(std::bad_alloc());
+    return p;
+  }
+
+  void deallocate(T* p, size_t) { free(p); }
+
+  constexpr friend auto operator==(allocator, allocator) noexcept -> bool {
+    return true;  // All instances of this allocator are equivalent.
+  }
+  constexpr friend auto operator!=(allocator, allocator) noexcept -> bool {
+    return false;
+  }
+};
+
+template <typename Formatter>
+FMT_CONSTEXPR auto maybe_set_debug_format(Formatter& f, bool set)
+    -> decltype(f.set_debug_format(set)) {
+  f.set_debug_format(set);
+}
+template <typename Formatter>
+FMT_CONSTEXPR void maybe_set_debug_format(Formatter&, ...) {}
+
 }  // namespace detail
 
 FMT_BEGIN_EXPORT
@@ -823,7 +793,7 @@ enum { inline_buffer_size = 500 };
  * converted to `std::string` with `to_string(out)`.
  */
 template <typename T, size_t SIZE = inline_buffer_size,
-          typename Allocator = std::allocator<T>>
+          typename Allocator = detail::allocator<T>>
 class basic_memory_buffer : public detail::buffer<T> {
  private:
   T store_[SIZE];
@@ -847,7 +817,7 @@ class basic_memory_buffer : public detail::buffer<T> {
     if (size > new_capacity)
       new_capacity = size;
     else if (new_capacity > max_size)
-      new_capacity = size > max_size ? size : max_size;
+      new_capacity = max_of(size, max_size);
     T* old_data = buf.data();
     T* new_data = self.alloc_.allocate(new_capacity);
     // Suppress a bogus -Wstringop-overflow in gcc 13.1 (#3481).
@@ -865,7 +835,7 @@ class basic_memory_buffer : public detail::buffer<T> {
   using value_type = T;
   using const_reference = const T&;
 
-  FMT_CONSTEXPR20 explicit basic_memory_buffer(
+  FMT_CONSTEXPR explicit basic_memory_buffer(
       const Allocator& alloc = Allocator())
       : detail::buffer<T>(grow), alloc_(alloc) {
     this->set(store_, SIZE);
@@ -874,11 +844,32 @@ class basic_memory_buffer : public detail::buffer<T> {
   FMT_CONSTEXPR20 ~basic_memory_buffer() { deallocate(); }
 
  private:
+  template <typename Alloc = Allocator,
+            FMT_ENABLE_IF(std::allocator_traits<Alloc>::
+                              propagate_on_container_move_assignment::value)>
+  FMT_CONSTEXPR20 auto move_alloc(basic_memory_buffer& other) -> bool {
+    alloc_ = std::move(other.alloc_);
+    return true;
+  }
+  // If the allocator does not propagate then copy the data from other.
+  template <typename Alloc = Allocator,
+            FMT_ENABLE_IF(!std::allocator_traits<Alloc>::
+                              propagate_on_container_move_assignment::value)>
+  FMT_CONSTEXPR20 auto move_alloc(basic_memory_buffer& other) -> bool {
+    T* data = other.data();
+    if (alloc_ == other.alloc_ || data == other.store_) return true;
+    size_t size = other.size();
+    // Perform copy operation, allocators are different.
+    this->resize(size);
+    detail::copy<T>(data, data + size, this->data());
+    return false;
+  }
+
   // Move data from other to this buffer.
   FMT_CONSTEXPR20 void move(basic_memory_buffer& other) {
-    alloc_ = std::move(other.alloc_);
     T* data = other.data();
     size_t size = other.size(), capacity = other.capacity();
+    if (!move_alloc(other)) return;
     if (data == other.store_) {
       this->set(store_, capacity);
       detail::copy<T>(other.store_, other.store_ + size, store_);
@@ -913,36 +904,69 @@ class basic_memory_buffer : public detail::buffer<T> {
 
   /// Resizes the buffer to contain `count` elements. If T is a POD type new
   /// elements may not be initialized.
-  FMT_CONSTEXPR20 void resize(size_t count) { this->try_resize(count); }
+  FMT_CONSTEXPR void resize(size_t count) { this->try_resize(count); }
 
   /// Increases the buffer capacity to `new_capacity`.
   void reserve(size_t new_capacity) { this->try_reserve(new_capacity); }
 
   using detail::buffer<T>::append;
   template <typename ContiguousRange>
-  void append(const ContiguousRange& range) {
+  FMT_CONSTEXPR20 void append(const ContiguousRange& range) {
     append(range.data(), range.data() + range.size());
   }
 };
 
 using memory_buffer = basic_memory_buffer<char>;
 
-template <typename T, size_t SIZE, typename Allocator>
-struct is_contiguous<basic_memory_buffer<T, SIZE, Allocator>> : std::true_type {
+template <size_t SIZE>
+FMT_NODISCARD auto to_string(const basic_memory_buffer<char, SIZE>& buf)
+    -> std::string {
+  auto size = buf.size();
+  detail::assume(size < std::string().max_size());
+  return {buf.data(), size};
+}
+
+// A writer to a buffered stream. It doesn't own the underlying stream.
+class writer {
+ private:
+  detail::buffer<char>* buf_;
+
+  // We cannot create a file buffer in advance because any write to a FILE may
+  // invalidate it.
+  FILE* file_;
+
+ public:
+  inline writer(FILE* f) : buf_(nullptr), file_(f) {}
+  inline writer(detail::buffer<char>& buf) : buf_(&buf) {}
+
+  /// Formats `args` according to specifications in `fmt` and writes the
+  /// output to the file.
+  template <typename... T> void print(format_string<T...> fmt, T&&... args) {
+    if (buf_)
+      fmt::format_to(appender(*buf_), fmt, std::forward<T>(args)...);
+    else
+      fmt::print(file_, fmt, std::forward<T>(args)...);
+  }
 };
 
-FMT_END_EXPORT
-namespace detail {
-FMT_API auto write_console(int fd, string_view text) -> bool;
-FMT_API void print(std::FILE*, string_view);
-}  // namespace detail
+class string_buffer {
+ private:
+  std::string str_;
+  detail::container_buffer<std::string> buf_;
 
-FMT_BEGIN_EXPORT
+ public:
+  inline string_buffer() : buf_(str_) {}
+
+  inline operator writer() { return buf_; }
+  inline auto str() -> std::string& { return str_; }
+};
+
+template <typename T, size_t SIZE, typename Allocator>
+struct is_contiguous<basic_memory_buffer<T, SIZE, Allocator>> : std::true_type {
+};
 
 // Suppress a misleading warning in older versions of clang.
-#if FMT_CLANG_VERSION
-#  pragma clang diagnostic ignored "-Wweak-vtables"
-#endif
+FMT_PRAGMA_CLANG(diagnostic ignored "-Wweak-vtables")
 
 /// An error reported from a formatting function.
 class FMT_SO_VISIBILITY("default") format_error : public std::runtime_error {
@@ -950,190 +974,94 @@ class FMT_SO_VISIBILITY("default") format_error : public std::runtime_error {
   using std::runtime_error::runtime_error;
 };
 
-namespace detail_exported {
-#if FMT_USE_NONTYPE_TEMPLATE_ARGS
+class loc_value;
+
+FMT_END_EXPORT
+namespace detail {
+FMT_API auto write_console(int fd, string_view text) -> bool;
+FMT_API void print(FILE*, string_view);
+}  // namespace detail
+
+namespace detail {
 template <typename Char, size_t N> struct fixed_string {
-  constexpr fixed_string(const Char (&str)[N]) {
-    detail::copy<Char, const Char*, Char*>(static_cast<const Char*>(str),
-                                           str + N, data);
+  FMT_CONSTEXPR20 fixed_string(const Char (&s)[N]) {
+    detail::copy<Char, const Char*, Char*>(static_cast<const Char*>(s), s + N,
+                                           data);
   }
   Char data[N] = {};
 };
-#endif
 
 // Converts a compile-time string to basic_string_view.
-template <typename Char, size_t N>
+FMT_EXPORT template <typename Char, size_t N>
 constexpr auto compile_string_to_view(const Char (&s)[N])
     -> basic_string_view<Char> {
   // Remove trailing NUL character if needed. Won't be present if this is used
   // with a raw character array (i.e. not defined as a string).
   return {s, N - (std::char_traits<Char>::to_int_type(s[N - 1]) == 0 ? 1 : 0)};
 }
-template <typename Char>
+FMT_EXPORT template <typename Char>
 constexpr auto compile_string_to_view(basic_string_view<Char> s)
     -> basic_string_view<Char> {
   return s;
 }
-}  // namespace detail_exported
 
-// A generic formatting context with custom output iterator and character
-// (code unit) support. Char is the format string code unit type which can be
-// different from OutputIt::value_type.
-template <typename OutputIt, typename Char> class generic_context {
- private:
-  OutputIt out_;
-  basic_format_args<generic_context> args_;
-  detail::locale_ref loc_;
+// Returns true if value is negative, false otherwise.
+// Same as `value < 0` but doesn't produce warnings if T is an unsigned type.
+template <typename T, FMT_ENABLE_IF(is_signed<T>::value)>
+constexpr auto is_negative(T value) -> bool {
+  return value < 0;
+}
+template <typename T, FMT_ENABLE_IF(!is_signed<T>::value)>
+constexpr auto is_negative(T) -> bool {
+  return false;
+}
 
- public:
-  using char_type = Char;
-  using iterator = OutputIt;
-  using parse_context_type = basic_format_parse_context<Char>;
-  template <typename T> using formatter_type = formatter<T, Char>;
+// Smallest of uint32_t, uint64_t, uint128_t that is large enough to
+// represent all values of an integral type T.
+template <typename T>
+using uint32_or_64_or_128_t =
+    conditional_t<num_bits<T>() <= 32 && !FMT_REDUCE_INT_INSTANTIATIONS,
+                  uint32_t,
+                  conditional_t<num_bits<T>() <= 64, uint64_t, uint128_t>>;
+template <typename T>
+using uint64_or_128_t = conditional_t<num_bits<T>() <= 64, uint64_t, uint128_t>;
 
-  constexpr generic_context(OutputIt out,
-                            basic_format_args<generic_context> ctx_args,
-                            detail::locale_ref loc = {})
-      : out_(out), args_(ctx_args), loc_(loc) {}
-  generic_context(generic_context&&) = default;
-  generic_context(const generic_context&) = delete;
-  void operator=(const generic_context&) = delete;
+#define FMT_POWERS_OF_10(factor)                                  \
+  factor * 10, (factor) * 100, (factor) * 1000, (factor) * 10000, \
+      (factor) * 100000, (factor) * 1000000, (factor) * 10000000, \
+      (factor) * 100000000, (factor) * 1000000000
 
-  constexpr auto arg(int id) const -> basic_format_arg<generic_context> {
-    return args_.get(id);
-  }
-  auto arg(basic_string_view<Char> name) -> basic_format_arg<generic_context> {
-    return args_.get(name);
-  }
-  FMT_CONSTEXPR auto arg_id(basic_string_view<Char> name) -> int {
-    return args_.get_id(name);
-  }
-  auto args() const -> const basic_format_args<generic_context>& {
-    return args_;
-  }
+// Converts value in the range [0, 100) to a string.
+// GCC generates slightly better code when value is pointer-size.
+inline auto digits2(size_t value) -> const char* {
+  // Align data since unaligned access may be slower when crossing a
+  // hardware-specific boundary.
+  alignas(2) static const char data[] =
+      "0001020304050607080910111213141516171819"
+      "2021222324252627282930313233343536373839"
+      "4041424344454647484950515253545556575859"
+      "6061626364656667686970717273747576777879"
+      "8081828384858687888990919293949596979899";
+  return &data[value * 2];
+}
 
-  FMT_CONSTEXPR auto out() -> iterator { return out_; }
+template <typename Char> constexpr auto getsign(sign s) -> Char {
+  return static_cast<char>(((' ' << 24) | ('+' << 16) | ('-' << 8)) >>
+                           (static_cast<int>(s) * 8));
+}
 
-  void advance_to(iterator it) {
-    if (!detail::is_back_insert_iterator<iterator>()) out_ = it;
-  }
-
-  FMT_CONSTEXPR auto locale() -> detail::locale_ref { return loc_; }
-};
-
-class loc_value {
- private:
-  basic_format_arg<format_context> value_;
-
- public:
-  template <typename T, FMT_ENABLE_IF(!detail::is_float128<T>::value)>
-  loc_value(T value) : value_(detail::make_arg<format_context>(value)) {}
-
-  template <typename T, FMT_ENABLE_IF(detail::is_float128<T>::value)>
-  loc_value(T) {}
-
-  template <typename Visitor> auto visit(Visitor&& vis) -> decltype(vis(0)) {
-    return value_.visit(vis);
-  }
-};
-
-// A locale facet that formats values in UTF-8.
-// It is parameterized on the locale to avoid the heavy <locale> include.
-template <typename Locale> class format_facet : public Locale::facet {
- private:
-  std::string separator_;
-  std::string grouping_;
-  std::string decimal_point_;
-
- protected:
-  virtual auto do_put(appender out, loc_value val,
-                      const format_specs& specs) const -> bool;
-
- public:
-  static FMT_API typename Locale::id id;
-
-  explicit format_facet(Locale& loc);
-  explicit format_facet(string_view sep = "",
-                        std::initializer_list<unsigned char> g = {3},
-                        std::string decimal_point = ".")
-      : separator_(sep.data(), sep.size()),
-        grouping_(g.begin(), g.end()),
-        decimal_point_(decimal_point) {}
-
-  auto put(appender out, loc_value val, const format_specs& specs) const
-      -> bool {
-    return do_put(out, val, specs);
-  }
-};
-
-FMT_END_EXPORT
-
-namespace detail {
-
-// Returns true if value is negative, false otherwise.
-// Same as `value < 0` but doesn't produce warnings if T is an unsigned type.
-template <typename T, FMT_ENABLE_IF(is_signed<T>::value)>
-constexpr auto is_negative(T value) -> bool {
-  return value < 0;
-}
-template <typename T, FMT_ENABLE_IF(!is_signed<T>::value)>
-constexpr auto is_negative(T) -> bool {
-  return false;
-}
-
-template <typename T>
-FMT_CONSTEXPR auto is_supported_floating_point(T) -> bool {
-  if (std::is_same<T, float>()) return FMT_USE_FLOAT;
-  if (std::is_same<T, double>()) return FMT_USE_DOUBLE;
-  if (std::is_same<T, long double>()) return FMT_USE_LONG_DOUBLE;
-  return true;
-}
-
-// Smallest of uint32_t, uint64_t, uint128_t that is large enough to
-// represent all values of an integral type T.
-template <typename T>
-using uint32_or_64_or_128_t =
-    conditional_t<num_bits<T>() <= 32 && !FMT_REDUCE_INT_INSTANTIATIONS,
-                  uint32_t,
-                  conditional_t<num_bits<T>() <= 64, uint64_t, uint128_t>>;
-template <typename T>
-using uint64_or_128_t = conditional_t<num_bits<T>() <= 64, uint64_t, uint128_t>;
-
-#define FMT_POWERS_OF_10(factor)                                  \
-  factor * 10, (factor) * 100, (factor) * 1000, (factor) * 10000, \
-      (factor) * 100000, (factor) * 1000000, (factor) * 10000000, \
-      (factor) * 100000000, (factor) * 1000000000
-
-// Converts value in the range [0, 100) to a string.
-constexpr auto digits2(size_t value) -> const char* {
-  // GCC generates slightly better code when value is pointer-size.
-  return &"0001020304050607080910111213141516171819"
-         "2021222324252627282930313233343536373839"
-         "4041424344454647484950515253545556575859"
-         "6061626364656667686970717273747576777879"
-         "8081828384858687888990919293949596979899"[value * 2];
-}
-
-// Sign is a template parameter to workaround a bug in gcc 4.8.
-template <typename Char, typename Sign> constexpr auto sign(Sign s) -> Char {
-#if !FMT_GCC_VERSION || FMT_GCC_VERSION >= 604
-  static_assert(std::is_same<Sign, sign_t>::value, "");
-#endif
-  return static_cast<Char>("\0-+ "[s]);
-}
-
-template <typename T> FMT_CONSTEXPR auto count_digits_fallback(T n) -> int {
-  int count = 1;
-  for (;;) {
-    // Integer division is slow so do it for a group of four digits instead
-    // of for every digit. The idea comes from the talk by Alexandrescu
-    // "Three Optimization Tips for C++". See speed-test for a comparison.
-    if (n < 10) return count;
-    if (n < 100) return count + 1;
-    if (n < 1000) return count + 2;
-    if (n < 10000) return count + 3;
-    n /= 10000u;
-    count += 4;
+template <typename T> FMT_CONSTEXPR auto count_digits_fallback(T n) -> int {
+  int count = 1;
+  for (;;) {
+    // Integer division is slow so do it for a group of four digits instead
+    // of for every digit. The idea comes from the talk by Alexandrescu
+    // "Three Optimization Tips for C++". See speed-test for a comparison.
+    if (n < 10) return count;
+    if (n < 100) return count + 1;
+    if (n < 1000) return count + 2;
+    if (n < 10000) return count + 3;
+    n /= 10000u;
+    count += 4;
   }
 }
 #if FMT_USE_INT128
@@ -1156,7 +1084,7 @@ inline auto do_count_digits(uint64_t n) -> int {
       10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15,
       15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20};
   auto t = bsr2log10[FMT_BUILTIN_CLZLL(n | 1) ^ 63];
-  static constexpr const uint64_t zero_or_powers_of_10[] = {
+  static constexpr uint64_t zero_or_powers_of_10[] = {
       0, 0, FMT_POWERS_OF_10(1U), FMT_POWERS_OF_10(1000000000ULL),
       10000000000000000000ULL};
   return t - (n < zero_or_powers_of_10[t]);
@@ -1167,7 +1095,7 @@ inline auto do_count_digits(uint64_t n) -> int {
 // except for n == 0 in which case count_digits returns 1.
 FMT_CONSTEXPR20 inline auto count_digits(uint64_t n) -> int {
 #ifdef FMT_BUILTIN_CLZLL
-  if (!is_constant_evaluated()) return do_count_digits(n);
+  if (!is_constant_evaluated() && !FMT_OPTIMIZE_SIZE) return do_count_digits(n);
 #endif
   return count_digits_fallback(n);
 }
@@ -1217,9 +1145,7 @@ FMT_INLINE auto do_count_digits(uint32_t n) -> int {
 // Optional version of count_digits for better performance on 32-bit platforms.
 FMT_CONSTEXPR20 inline auto count_digits(uint32_t n) -> int {
 #ifdef FMT_BUILTIN_CLZ
-  if (!is_constant_evaluated()) {
-    return do_count_digits(n);
-  }
+  if (!is_constant_evaluated() && !FMT_OPTIMIZE_SIZE) return do_count_digits(n);
 #endif
   return count_digits_fallback(n);
 }
@@ -1256,6 +1182,17 @@ template <> inline auto decimal_point(locale_ref loc) -> wchar_t {
   return decimal_point_impl<wchar_t>(loc);
 }
 
+#ifndef FMT_HEADER_ONLY
+FMT_BEGIN_EXPORT
+extern template FMT_API auto thousands_sep_impl<char>(locale_ref)
+    -> thousands_sep_result<char>;
+extern template FMT_API auto thousands_sep_impl<wchar_t>(locale_ref)
+    -> thousands_sep_result<wchar_t>;
+extern template FMT_API auto decimal_point_impl(locale_ref) -> char;
+extern template FMT_API auto decimal_point_impl(locale_ref) -> wchar_t;
+FMT_END_EXPORT
+#endif  // FMT_HEADER_ONLY
+
 // Compares two characters for equality.
 template <typename Char> auto equal2(const Char* lhs, const char* rhs) -> bool {
   return lhs[0] == Char(rhs[0]) && lhs[1] == Char(rhs[1]);
@@ -1264,82 +1201,98 @@ inline auto equal2(const char* lhs, const char* rhs) -> bool {
   return memcmp(lhs, rhs, 2) == 0;
 }
 
-// Copies two characters from src to dst.
+// Writes a two-digit value to out.
 template <typename Char>
-FMT_CONSTEXPR20 FMT_INLINE void copy2(Char* dst, const char* src) {
-  if (!is_constant_evaluated() && sizeof(Char) == sizeof(char)) {
-    memcpy(dst, src, 2);
+FMT_CONSTEXPR20 FMT_INLINE void write2digits(Char* out, size_t value) {
+  if (!is_constant_evaluated() && std::is_same<Char, char>::value &&
+      !FMT_OPTIMIZE_SIZE) {
+    memcpy(out, digits2(value), 2);
     return;
   }
-  *dst++ = static_cast<Char>(*src++);
-  *dst = static_cast<Char>(*src);
+  *out++ = static_cast<Char>('0' + value / 10);
+  *out = static_cast<Char>('0' + value % 10);
 }
 
-template <typename Iterator> struct format_decimal_result {
-  Iterator begin;
-  Iterator end;
-};
-
-// Formats a decimal unsigned integer value writing into out pointing to a
-// buffer of specified size. The caller must ensure that the buffer is large
-// enough.
+// Formats a decimal unsigned integer value writing to out pointing to a buffer
+// of specified size. The caller must ensure that the buffer is large enough.
 template <typename Char, typename UInt>
-FMT_CONSTEXPR20 auto format_decimal(Char* out, UInt value, int size)
-    -> format_decimal_result<Char*> {
+FMT_CONSTEXPR20 auto do_format_decimal(Char* out, UInt value, int size)
+    -> Char* {
   FMT_ASSERT(size >= count_digits(value), "invalid digit count");
-  out += size;
-  Char* end = out;
+  unsigned n = to_unsigned(size);
   while (value >= 100) {
     // Integer division is slow so do it for a group of two digits instead
     // of for every digit. The idea comes from the talk by Alexandrescu
     // "Three Optimization Tips for C++". See speed-test for a comparison.
-    out -= 2;
-    copy2(out, digits2(static_cast<size_t>(value % 100)));
+    n -= 2;
+    write2digits(out + n, static_cast<unsigned>(value % 100));
     value /= 100;
   }
-  if (value < 10) {
-    *--out = static_cast<Char>('0' + value);
-    return {out, end};
+  if (value >= 10) {
+    n -= 2;
+    write2digits(out + n, static_cast<unsigned>(value));
+  } else {
+    out[--n] = static_cast<Char>('0' + value);
   }
-  out -= 2;
-  copy2(out, digits2(static_cast<size_t>(value)));
-  return {out, end};
+  return out + n;
+}
+
+template <typename Char, typename UInt>
+FMT_CONSTEXPR FMT_INLINE auto format_decimal(Char* out, UInt value,
+                                             int num_digits) -> Char* {
+  do_format_decimal(out, value, num_digits);
+  return out + num_digits;
 }
 
-template <typename Char, typename UInt, typename Iterator,
-          FMT_ENABLE_IF(!std::is_pointer<remove_cvref_t<Iterator>>::value)>
-FMT_CONSTEXPR inline auto format_decimal(Iterator out, UInt value, int size)
-    -> format_decimal_result<Iterator> {
+template <typename Char, typename UInt, typename OutputIt,
+          FMT_ENABLE_IF(!std::is_pointer<remove_cvref_t<OutputIt>>::value)>
+FMT_CONSTEXPR auto format_decimal(OutputIt out, UInt value, int num_digits)
+    -> OutputIt {
+  if (auto ptr = to_pointer<Char>(out, to_unsigned(num_digits))) {
+    do_format_decimal(ptr, value, num_digits);
+    return out;
+  }
   // Buffer is large enough to hold all digits (digits10 + 1).
-  Char buffer[digits10<UInt>() + 1] = {};
-  auto end = format_decimal(buffer, value, size).end;
-  return {out, detail::copy_noinline<Char>(buffer, end, out)};
+  char buffer[digits10<UInt>() + 1];
+  if (is_constant_evaluated()) fill_n(buffer, sizeof(buffer), '\0');
+  do_format_decimal(buffer, value, num_digits);
+  return copy_noinline<Char>(buffer, buffer + num_digits, out);
 }
 
-template <unsigned BASE_BITS, typename Char, typename UInt>
-FMT_CONSTEXPR auto format_uint(Char* buffer, UInt value, int num_digits,
-                               bool upper = false) -> Char* {
-  buffer += num_digits;
-  Char* end = buffer;
+template <typename Char, typename UInt>
+FMT_CONSTEXPR auto do_format_base2e(int base_bits, Char* out, UInt value,
+                                    int size, bool upper = false) -> Char* {
+  out += size;
   do {
     const char* digits = upper ? "0123456789ABCDEF" : "0123456789abcdef";
-    unsigned digit = static_cast<unsigned>(value & ((1 << BASE_BITS) - 1));
-    *--buffer = static_cast<Char>(BASE_BITS < 4 ? static_cast<char>('0' + digit)
-                                                : digits[digit]);
-  } while ((value >>= BASE_BITS) != 0);
-  return end;
+    unsigned digit = static_cast<unsigned>(value & ((1u << base_bits) - 1));
+    *--out = static_cast<Char>(base_bits < 4 ? static_cast<char>('0' + digit)
+                                             : digits[digit]);
+  } while ((value >>= base_bits) != 0);
+  return out;
+}
+
+// Formats an unsigned integer in the power of two base (binary, octal, hex).
+template <typename Char, typename UInt>
+FMT_CONSTEXPR auto format_base2e(int base_bits, Char* out, UInt value,
+                                 int num_digits, bool upper = false) -> Char* {
+  do_format_base2e(base_bits, out, value, num_digits, upper);
+  return out + num_digits;
 }
 
-template <unsigned BASE_BITS, typename Char, typename It, typename UInt>
-FMT_CONSTEXPR inline auto format_uint(It out, UInt value, int num_digits,
-                                      bool upper = false) -> It {
+template <typename Char, typename OutputIt, typename UInt,
+          FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value)>
+FMT_CONSTEXPR inline auto format_base2e(int base_bits, OutputIt out, UInt value,
+                                        int num_digits, bool upper = false)
+    -> OutputIt {
   if (auto ptr = to_pointer<Char>(out, to_unsigned(num_digits))) {
-    format_uint<BASE_BITS>(ptr, value, num_digits, upper);
+    format_base2e(base_bits, ptr, value, num_digits, upper);
     return out;
   }
-  // Buffer should be large enough to hold all digits (digits / BASE_BITS + 1).
-  char buffer[num_bits<UInt>() / BASE_BITS + 1] = {};
-  format_uint<BASE_BITS>(buffer, value, num_digits, upper);
+  // Make buffer large enough for any base.
+  char buffer[num_bits<UInt>()];
+  if (is_constant_evaluated()) fill_n(buffer, sizeof(buffer), '\0');
+  format_base2e(base_bits, buffer, value, num_digits, upper);
   return detail::copy_noinline<Char>(buffer, buffer + num_digits, out);
 }
 
@@ -1350,10 +1303,12 @@ class utf8_to_utf16 {
 
  public:
   FMT_API explicit utf8_to_utf16(string_view s);
-  operator basic_string_view<wchar_t>() const { return {&buffer_[0], size()}; }
-  auto size() const -> size_t { return buffer_.size() - 1; }
-  auto c_str() const -> const wchar_t* { return &buffer_[0]; }
-  auto str() const -> std::wstring { return {&buffer_[0], size()}; }
+  inline operator basic_string_view<wchar_t>() const {
+    return {&buffer_[0], size()};
+  }
+  inline auto size() const -> size_t { return buffer_.size() - 1; }
+  inline auto c_str() const -> const wchar_t* { return &buffer_[0]; }
+  inline auto str() const -> std::wstring { return {&buffer_[0], size()}; }
 };
 
 enum class to_utf8_error_policy { abort, replace };
@@ -1368,10 +1323,11 @@ template <typename WChar, typename Buffer = memory_buffer> class to_utf8 {
   explicit to_utf8(basic_string_view<WChar> s,
                    to_utf8_error_policy policy = to_utf8_error_policy::abort) {
     static_assert(sizeof(WChar) == 2 || sizeof(WChar) == 4,
-                  "Expect utf16 or utf32");
-    if (!convert(s, policy))
+                  "expected utf16 or utf32");
+    if (!convert(s, policy)) {
       FMT_THROW(std::runtime_error(sizeof(WChar) == 2 ? "invalid utf16"
                                                       : "invalid utf32"));
+    }
   }
   operator string_view() const { return string_view(&buffer_[0], size()); }
   auto size() const -> size_t { return buffer_.size() - 1; }
@@ -1400,10 +1356,11 @@ template <typename WChar, typename Buffer = memory_buffer> class to_utf8 {
           if (policy == to_utf8_error_policy::abort) return false;
           buf.append(string_view("\xEF\xBF\xBD"));
           --p;
-        } else {
-          c = (c << 10) + static_cast<uint32_t>(*p) - 0x35fdc00;
+          continue;
         }
-      } else if (c < 0x80) {
+        c = (c << 10) + static_cast<uint32_t>(*p) - 0x35fdc00;
+      }
+      if (c < 0x80) {
         buf.push_back(static_cast<char>(c));
       } else if (c < 0x800) {
         buf.push_back(static_cast<char>(0xc0 | (c >> 6)));
@@ -1426,7 +1383,7 @@ template <typename WChar, typename Buffer = memory_buffer> class to_utf8 {
 };
 
 // Computes 128-bit result of multiplication of two 64-bit unsigned integers.
-inline auto umul128(uint64_t x, uint64_t y) noexcept -> uint128_fallback {
+FMT_INLINE auto umul128(uint64_t x, uint64_t y) noexcept -> uint128_fallback {
 #if FMT_USE_INT128
   auto p = static_cast<uint128_opt>(x) * static_cast<uint128_opt>(y);
   return {static_cast<uint64_t>(p >> 64), static_cast<uint64_t>(p)};
@@ -1570,26 +1527,38 @@ template <typename Float> constexpr auto exponent_bias() -> int {
                               : std::numeric_limits<Float>::max_exponent - 1;
 }
 
+FMT_CONSTEXPR inline auto compute_exp_size(int exp) -> int {
+  auto prefix_size = 2;  // sign + 'e'
+  auto abs_exp = exp >= 0 ? exp : -exp;
+  if (abs_exp < 100) return prefix_size + 2;
+  return prefix_size + (abs_exp >= 1000 ? 4 : 3);
+}
+
 // Writes the exponent exp in the form "[+-]d{2,3}" to buffer.
-template <typename Char, typename It>
-FMT_CONSTEXPR auto write_exponent(int exp, It it) -> It {
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR auto write_exponent(int exp, OutputIt out) -> OutputIt {
   FMT_ASSERT(-10000 < exp && exp < 10000, "exponent out of range");
   if (exp < 0) {
-    *it++ = static_cast<Char>('-');
+    *out++ = static_cast<Char>('-');
     exp = -exp;
   } else {
-    *it++ = static_cast<Char>('+');
-  }
-  if (exp >= 100) {
-    const char* top = digits2(to_unsigned(exp / 100));
-    if (exp >= 1000) *it++ = static_cast<Char>(top[0]);
-    *it++ = static_cast<Char>(top[1]);
-    exp %= 100;
+    *out++ = static_cast<Char>('+');
   }
-  const char* d = digits2(to_unsigned(exp));
-  *it++ = static_cast<Char>(d[0]);
-  *it++ = static_cast<Char>(d[1]);
-  return it;
+  auto uexp = static_cast<uint32_t>(exp);
+  if (is_constant_evaluated()) {
+    if (uexp < 10) *out++ = '0';
+    return format_decimal<Char>(out, uexp, count_digits(uexp));
+  }
+  if (uexp >= 100u) {
+    const char* top = digits2(uexp / 100);
+    if (uexp >= 1000u) *out++ = static_cast<Char>(top[0]);
+    *out++ = static_cast<Char>(top[1]);
+    uexp %= 100;
+  }
+  const char* d = digits2(uexp);
+  *out++ = static_cast<Char>(d[0]);
+  *out++ = static_cast<Char>(d[1]);
+  return out;
 }
 
 // A floating-point number f * pow(2, e) where F is an unsigned type.
@@ -1597,7 +1566,7 @@ template <typename F> struct basic_fp {
   F f;
   int e;
 
-  static constexpr const int num_significand_bits =
+  static constexpr int num_significand_bits =
       static_cast<int>(sizeof(F) * num_bits<unsigned char>());
 
   constexpr basic_fp() : f(0), e(0) {}
@@ -1690,12 +1659,21 @@ constexpr auto convert_float(T value) -> convert_float_result<T> {
   return static_cast<convert_float_result<T>>(value);
 }
 
+template <bool C, typename T, typename F, FMT_ENABLE_IF(C)>
+auto select(T true_value, F) -> T {
+  return true_value;
+}
+template <bool C, typename T, typename F, FMT_ENABLE_IF(!C)>
+auto select(T, F false_value) -> F {
+  return false_value;
+}
+
 template <typename Char, typename OutputIt>
-FMT_NOINLINE FMT_CONSTEXPR auto fill(OutputIt it, size_t n, const fill_t& fill)
-    -> OutputIt {
-  auto fill_size = fill.size();
-  if (fill_size == 1) return detail::fill_n(it, n, fill.template get<Char>());
-  if (const Char* data = fill.template data<Char>()) {
+FMT_CONSTEXPR FMT_NOINLINE auto fill(OutputIt it, size_t n,
+                                     const basic_specs& specs) -> OutputIt {
+  auto fill_size = specs.fill_size();
+  if (fill_size == 1) return detail::fill_n(it, n, specs.fill_unit<Char>());
+  if (const Char* data = specs.fill<Char>()) {
     for (size_t i = 0; i < n; ++i) it = copy<Char>(data, data + fill_size, it);
   }
   return it;
@@ -1704,36 +1682,38 @@ FMT_NOINLINE FMT_CONSTEXPR auto fill(OutputIt it, size_t n, const fill_t& fill)
 // Writes the output of f, padded according to format specifications in specs.
 // size: output size in code units.
 // width: output display width in (terminal) column positions.
-template <typename Char, align::type align = align::left, typename OutputIt,
+template <typename Char, align default_align = align::left, typename OutputIt,
           typename F>
 FMT_CONSTEXPR auto write_padded(OutputIt out, const format_specs& specs,
                                 size_t size, size_t width, F&& f) -> OutputIt {
-  static_assert(align == align::left || align == align::right, "");
+  static_assert(default_align == align::left || default_align == align::right,
+                "");
   unsigned spec_width = to_unsigned(specs.width);
   size_t padding = spec_width > width ? spec_width - width : 0;
   // Shifts are encoded as string literals because static constexpr is not
   // supported in constexpr functions.
-  auto* shifts = align == align::left ? "\x1f\x1f\x00\x01" : "\x00\x1f\x00\x01";
-  size_t left_padding = padding >> shifts[specs.align];
+  auto* shifts =
+      default_align == align::left ? "\x1f\x1f\x00\x01" : "\x00\x1f\x00\x01";
+  size_t left_padding = padding >> shifts[static_cast<int>(specs.align())];
   size_t right_padding = padding - left_padding;
-  auto it = reserve(out, size + padding * specs.fill.size());
-  if (left_padding != 0) it = fill<Char>(it, left_padding, specs.fill);
+  auto it = reserve(out, size + padding * specs.fill_size());
+  if (left_padding != 0) it = fill<Char>(it, left_padding, specs);
   it = f(it);
-  if (right_padding != 0) it = fill<Char>(it, right_padding, specs.fill);
+  if (right_padding != 0) it = fill<Char>(it, right_padding, specs);
   return base_iterator(out, it);
 }
 
-template <typename Char, align::type align = align::left, typename OutputIt,
+template <typename Char, align default_align = align::left, typename OutputIt,
           typename F>
 constexpr auto write_padded(OutputIt out, const format_specs& specs,
                             size_t size, F&& f) -> OutputIt {
-  return write_padded<Char, align>(out, specs, size, size, f);
+  return write_padded<Char, default_align>(out, specs, size, size, f);
 }
 
-template <typename Char, align::type align = align::left, typename OutputIt>
+template <typename Char, align default_align = align::left, typename OutputIt>
 FMT_CONSTEXPR auto write_bytes(OutputIt out, string_view bytes,
                                const format_specs& specs = {}) -> OutputIt {
-  return write_padded<Char, align>(
+  return write_padded<Char, default_align>(
       out, specs, bytes.size(), [bytes](reserve_iterator<OutputIt> it) {
         const char* data = bytes.data();
         return copy<Char>(data, data + bytes.size(), it);
@@ -1748,7 +1728,7 @@ auto write_ptr(OutputIt out, UIntPtr value, const format_specs* specs)
   auto write = [=](reserve_iterator<OutputIt> it) {
     *it++ = static_cast<Char>('0');
     *it++ = static_cast<Char>('x');
-    return format_uint<4, Char>(it, value, num_digits);
+    return format_base2e<Char>(4, it, value, num_digits);
   };
   return specs ? write_padded<Char, align::right>(out, *specs, size, write)
                : base_iterator(out, write(reserve(out, size)));
@@ -1758,8 +1738,9 @@ auto write_ptr(OutputIt out, UIntPtr value, const format_specs* specs)
 FMT_API auto is_printable(uint32_t cp) -> bool;
 
 inline auto needs_escape(uint32_t cp) -> bool {
-  return cp < 0x20 || cp == 0x7f || cp == '"' || cp == '\\' ||
-         !is_printable(cp);
+  if (cp < 0x20 || cp == 0x7f || cp == '"' || cp == '\\') return true;
+  if (const_check(FMT_OPTIMIZE_SIZE > 1)) return false;
+  return !is_printable(cp);
 }
 
 template <typename Char> struct find_escape_result {
@@ -1781,7 +1762,7 @@ auto find_escape(const Char* begin, const Char* end)
 
 inline auto find_escape(const char* begin, const char* end)
     -> find_escape_result<char> {
-  if (!use_utf8()) return find_escape<char>(begin, end);
+  if (const_check(!use_utf8)) return find_escape<char>(begin, end);
   auto result = find_escape_result<char>{end, nullptr, 0};
   for_each_codepoint(string_view(begin, to_unsigned(end - begin)),
                      [&](uint32_t cp, string_view sv) {
@@ -1794,37 +1775,13 @@ inline auto find_escape(const char* begin, const char* end)
   return result;
 }
 
-#define FMT_STRING_IMPL(s, base, explicit)                                    \
-  [] {                                                                        \
-    /* Use the hidden visibility as a workaround for a GCC bug (#1973). */    \
-    /* Use a macro-like name to avoid shadowing warnings. */                  \
-    struct FMT_VISIBILITY("hidden") FMT_COMPILE_STRING : base {               \
-      using char_type FMT_MAYBE_UNUSED = fmt::remove_cvref_t<decltype(s[0])>; \
-      FMT_MAYBE_UNUSED FMT_CONSTEXPR explicit                                 \
-      operator fmt::basic_string_view<char_type>() const {                    \
-        return fmt::detail_exported::compile_string_to_view<char_type>(s);    \
-      }                                                                       \
-    };                                                                        \
-    return FMT_COMPILE_STRING();                                              \
-  }()
-
-/**
- * Constructs a compile-time format string from a string literal `s`.
- *
- * **Example**:
- *
- *     // A compile-time error because 'd' is an invalid specifier for strings.
- *     std::string s = fmt::format(FMT_STRING("{:d}"), "foo");
- */
-#define FMT_STRING(s) FMT_STRING_IMPL(s, fmt::detail::compile_string, )
-
 template <size_t width, typename Char, typename OutputIt>
 auto write_codepoint(OutputIt out, char prefix, uint32_t cp) -> OutputIt {
   *out++ = static_cast<Char>('\\');
   *out++ = static_cast<Char>(prefix);
   Char buf[width];
   fill_n(buf, width, static_cast<Char>('0'));
-  format_uint<4>(buf, cp, width);
+  format_base2e(4, buf, cp, width);
   return copy<Char>(buf, buf + width, out);
 }
 
@@ -1845,13 +1802,9 @@ auto write_escaped_cp(OutputIt out, const find_escape_result<Char>& escape)
     *out++ = static_cast<Char>('\\');
     c = static_cast<Char>('t');
     break;
-  case '"':
-    FMT_FALLTHROUGH;
-  case '\'':
-    FMT_FALLTHROUGH;
-  case '\\':
-    *out++ = static_cast<Char>('\\');
-    break;
+  case '"':  FMT_FALLTHROUGH;
+  case '\'': FMT_FALLTHROUGH;
+  case '\\': *out++ = static_cast<Char>('\\'); break;
   default:
     if (escape.cp < 0x100) return write_codepoint<2, Char>(out, 'x', escape.cp);
     if (escape.cp < 0x10000)
@@ -1904,73 +1857,13 @@ auto write_escaped_char(OutputIt out, Char v) -> OutputIt {
 template <typename Char, typename OutputIt>
 FMT_CONSTEXPR auto write_char(OutputIt out, Char value,
                               const format_specs& specs) -> OutputIt {
-  bool is_debug = specs.type == presentation_type::debug;
+  bool is_debug = specs.type() == presentation_type::debug;
   return write_padded<Char>(out, specs, 1, [=](reserve_iterator<OutputIt> it) {
     if (is_debug) return write_escaped_char(it, value);
     *it++ = value;
     return it;
   });
 }
-template <typename Char, typename OutputIt>
-FMT_CONSTEXPR auto write(OutputIt out, Char value, const format_specs& specs,
-                         locale_ref loc = {}) -> OutputIt {
-  // char is formatted as unsigned char for consistency across platforms.
-  using unsigned_type =
-      conditional_t<std::is_same<Char, char>::value, unsigned char, unsigned>;
-  return check_char_specs(specs)
-             ? write_char<Char>(out, value, specs)
-             : write<Char>(out, static_cast<unsigned_type>(value), specs, loc);
-}
-
-// Data for write_int that doesn't depend on output iterator type. It is used to
-// avoid template code bloat.
-template <typename Char> struct write_int_data {
-  size_t size;
-  size_t padding;
-
-  FMT_CONSTEXPR write_int_data(int num_digits, unsigned prefix,
-                               const format_specs& specs)
-      : size((prefix >> 24) + to_unsigned(num_digits)), padding(0) {
-    if (specs.align == align::numeric) {
-      auto width = to_unsigned(specs.width);
-      if (width > size) {
-        padding = width - size;
-        size = width;
-      }
-    } else if (specs.precision > num_digits) {
-      size = (prefix >> 24) + to_unsigned(specs.precision);
-      padding = to_unsigned(specs.precision - num_digits);
-    }
-  }
-};
-
-// Writes an integer in the format
-//   <left-padding><prefix><numeric-padding><digits><right-padding>
-// where <digits> are written by write_digits(it).
-// prefix contains chars in three lower bytes and the size in the fourth byte.
-template <typename Char, typename OutputIt, typename W>
-FMT_CONSTEXPR FMT_INLINE auto write_int(OutputIt out, int num_digits,
-                                        unsigned prefix,
-                                        const format_specs& specs,
-                                        W write_digits) -> OutputIt {
-  // Slightly faster check for specs.width == 0 && specs.precision == -1.
-  if ((specs.width | (specs.precision + 1)) == 0) {
-    auto it = reserve(out, to_unsigned(num_digits) + (prefix >> 24));
-    if (prefix != 0) {
-      for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
-        *it++ = static_cast<Char>(p & 0xff);
-    }
-    return base_iterator(out, write_digits(it));
-  }
-  auto data = write_int_data<Char>(num_digits, prefix, specs);
-  return write_padded<Char, align::right>(
-      out, specs, data.size, [=](reserve_iterator<OutputIt> it) {
-        for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
-          *it++ = static_cast<Char>(p & 0xff);
-        it = detail::fill_n(it, data.padding, static_cast<Char>('0'));
-        return write_digits(it);
-      });
-}
 
 template <typename Char> class digit_grouping {
  private:
@@ -2012,7 +1905,7 @@ template <typename Char> class digit_grouping {
     return count;
   }
 
-  // Applies grouping to digits and write the output to out.
+  // Applies grouping to digits and writes the output to out.
   template <typename Out, typename C>
   auto apply(Out out, basic_string_view<C> digits) const -> Out {
     auto num_digits = static_cast<int>(digits.size());
@@ -2049,34 +1942,32 @@ auto write_int(OutputIt out, UInt value, unsigned prefix,
   static_assert(std::is_same<uint64_or_128_t<UInt>, UInt>::value, "");
   int num_digits = 0;
   auto buffer = memory_buffer();
-  switch (specs.type) {
-  default:
-    FMT_ASSERT(false, "");
-    FMT_FALLTHROUGH;
+  switch (specs.type()) {
+  default: FMT_ASSERT(false, ""); FMT_FALLTHROUGH;
   case presentation_type::none:
   case presentation_type::dec:
     num_digits = count_digits(value);
     format_decimal<char>(appender(buffer), value, num_digits);
     break;
   case presentation_type::hex:
-    if (specs.alt)
-      prefix_append(prefix, unsigned(specs.upper ? 'X' : 'x') << 8 | '0');
+    if (specs.alt())
+      prefix_append(prefix, unsigned(specs.upper() ? 'X' : 'x') << 8 | '0');
     num_digits = count_digits<4>(value);
-    format_uint<4, char>(appender(buffer), value, num_digits, specs.upper);
+    format_base2e<char>(4, appender(buffer), value, num_digits, specs.upper());
     break;
   case presentation_type::oct:
     num_digits = count_digits<3>(value);
     // Octal prefix '0' is counted as a digit, so only add it if precision
     // is not greater than the number of digits.
-    if (specs.alt && specs.precision <= num_digits && value != 0)
+    if (specs.alt() && specs.precision <= num_digits && value != 0)
       prefix_append(prefix, '0');
-    format_uint<3, char>(appender(buffer), value, num_digits);
+    format_base2e<char>(3, appender(buffer), value, num_digits);
     break;
   case presentation_type::bin:
-    if (specs.alt)
-      prefix_append(prefix, unsigned(specs.upper ? 'B' : 'b') << 8 | '0');
+    if (specs.alt())
+      prefix_append(prefix, unsigned(specs.upper() ? 'B' : 'b') << 8 | '0');
     num_digits = count_digits<1>(value);
-    format_uint<1, char>(appender(buffer), value, num_digits);
+    format_base2e<char>(1, appender(buffer), value, num_digits);
     break;
   case presentation_type::chr:
     return write_char<Char>(out, static_cast<Char>(value), specs);
@@ -2092,12 +1983,16 @@ auto write_int(OutputIt out, UInt value, unsigned prefix,
       });
 }
 
+#if FMT_USE_LOCALE
 // Writes a localized value.
 FMT_API auto write_loc(appender out, loc_value value, const format_specs& specs,
                        locale_ref loc) -> bool;
+auto write_loc(basic_appender<wchar_t> out, loc_value value,
+               const format_specs& specs, locale_ref loc) -> bool;
+#endif
 template <typename OutputIt>
-inline auto write_loc(OutputIt, loc_value, const format_specs&, locale_ref)
-    -> bool {
+inline auto write_loc(OutputIt, const loc_value&, const format_specs&,
+                      locale_ref) -> bool {
   return false;
 }
 
@@ -2107,7 +2002,7 @@ template <typename UInt> struct write_int_arg {
 };
 
 template <typename T>
-FMT_CONSTEXPR auto make_write_int_arg(T value, sign_t sign)
+FMT_CONSTEXPR auto make_write_int_arg(T value, sign s)
     -> write_int_arg<uint32_or_64_or_128_t<T>> {
   auto prefix = 0u;
   auto abs_value = static_cast<uint32_or_64_or_128_t<T>>(value);
@@ -2115,9 +2010,8 @@ FMT_CONSTEXPR auto make_write_int_arg(T value, sign_t sign)
     prefix = 0x01000000 | '-';
     abs_value = 0 - abs_value;
   } else {
-    constexpr const unsigned prefixes[4] = {0, 0, 0x1000000u | '+',
-                                            0x1000000u | ' '};
-    prefix = prefixes[sign];
+    constexpr unsigned prefixes[4] = {0, 0, 0x1000000u | '+', 0x1000000u | ' '};
+    prefix = prefixes[static_cast<int>(s)];
   }
   return {abs_value, prefix};
 }
@@ -2131,7 +2025,7 @@ template <typename Char = char> struct loc_writer {
 
   template <typename T, FMT_ENABLE_IF(is_integer<T>::value)>
   auto operator()(T value) -> bool {
-    auto arg = make_write_int_arg(value, specs.sign);
+    auto arg = make_write_int_arg(value, specs.sign());
     write_int(out, static_cast<uint64_or_128_t<T>>(arg.abs_value), arg.prefix,
               specs, digit_grouping<Char>(grouping, sep));
     return true;
@@ -2143,65 +2037,99 @@ template <typename Char = char> struct loc_writer {
   }
 };
 
+// Size and padding computation separate from write_int to avoid template bloat.
+struct size_padding {
+  unsigned size;
+  unsigned padding;
+
+  FMT_CONSTEXPR size_padding(int num_digits, unsigned prefix,
+                             const format_specs& specs)
+      : size((prefix >> 24) + to_unsigned(num_digits)), padding(0) {
+    if (specs.align() == align::numeric) {
+      auto width = to_unsigned(specs.width);
+      if (width > size) {
+        padding = width - size;
+        size = width;
+      }
+    } else if (specs.precision > num_digits) {
+      size = (prefix >> 24) + to_unsigned(specs.precision);
+      padding = to_unsigned(specs.precision - num_digits);
+    }
+  }
+};
+
 template <typename Char, typename OutputIt, typename T>
 FMT_CONSTEXPR FMT_INLINE auto write_int(OutputIt out, write_int_arg<T> arg,
-                                        const format_specs& specs, locale_ref)
-    -> OutputIt {
+                                        const format_specs& specs) -> OutputIt {
   static_assert(std::is_same<T, uint32_or_64_or_128_t<T>>::value, "");
+
+  constexpr size_t buffer_size = num_bits<T>();
+  char buffer[buffer_size];
+  if (is_constant_evaluated()) fill_n(buffer, buffer_size, '\0');
+  const char* begin = nullptr;
+  const char* end = buffer + buffer_size;
+
   auto abs_value = arg.abs_value;
   auto prefix = arg.prefix;
-  switch (specs.type) {
-  default:
-    FMT_ASSERT(false, "");
-    FMT_FALLTHROUGH;
+  switch (specs.type()) {
+  default: FMT_ASSERT(false, ""); FMT_FALLTHROUGH;
   case presentation_type::none:
-  case presentation_type::dec: {
-    int num_digits = count_digits(abs_value);
-    return write_int<Char>(
-        out, num_digits, prefix, specs, [=](reserve_iterator<OutputIt> it) {
-          return format_decimal<Char>(it, abs_value, num_digits).end;
-        });
-  }
-  case presentation_type::hex: {
-    if (specs.alt)
-      prefix_append(prefix, unsigned(specs.upper ? 'X' : 'x') << 8 | '0');
-    int num_digits = count_digits<4>(abs_value);
-    return write_int<Char>(
-        out, num_digits, prefix, specs, [=](reserve_iterator<OutputIt> it) {
-          return format_uint<4, Char>(it, abs_value, num_digits, specs.upper);
-        });
-  }
+  case presentation_type::dec:
+    begin = do_format_decimal(buffer, abs_value, buffer_size);
+    break;
+  case presentation_type::hex:
+    begin = do_format_base2e(4, buffer, abs_value, buffer_size, specs.upper());
+    if (specs.alt())
+      prefix_append(prefix, unsigned(specs.upper() ? 'X' : 'x') << 8 | '0');
+    break;
   case presentation_type::oct: {
-    int num_digits = count_digits<3>(abs_value);
+    begin = do_format_base2e(3, buffer, abs_value, buffer_size);
     // Octal prefix '0' is counted as a digit, so only add it if precision
     // is not greater than the number of digits.
-    if (specs.alt && specs.precision <= num_digits && abs_value != 0)
+    auto num_digits = end - begin;
+    if (specs.alt() && specs.precision <= num_digits && abs_value != 0)
       prefix_append(prefix, '0');
-    return write_int<Char>(
-        out, num_digits, prefix, specs, [=](reserve_iterator<OutputIt> it) {
-          return format_uint<3, Char>(it, abs_value, num_digits);
-        });
-  }
-  case presentation_type::bin: {
-    if (specs.alt)
-      prefix_append(prefix, unsigned(specs.upper ? 'B' : 'b') << 8 | '0');
-    int num_digits = count_digits<1>(abs_value);
-    return write_int<Char>(
-        out, num_digits, prefix, specs, [=](reserve_iterator<OutputIt> it) {
-          return format_uint<1, Char>(it, abs_value, num_digits);
-        });
+    break;
   }
+  case presentation_type::bin:
+    begin = do_format_base2e(1, buffer, abs_value, buffer_size);
+    if (specs.alt())
+      prefix_append(prefix, unsigned(specs.upper() ? 'B' : 'b') << 8 | '0');
+    break;
   case presentation_type::chr:
     return write_char<Char>(out, static_cast<Char>(abs_value), specs);
   }
+
+  // Write an integer in the format
+  //   <left-padding><prefix><numeric-padding><digits><right-padding>
+  // prefix contains chars in three lower bytes and the size in the fourth byte.
+  int num_digits = static_cast<int>(end - begin);
+  // Slightly faster check for specs.width == 0 && specs.precision == -1.
+  if ((specs.width | (specs.precision + 1)) == 0) {
+    auto it = reserve(out, to_unsigned(num_digits) + (prefix >> 24));
+    for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
+      *it++ = static_cast<Char>(p & 0xff);
+    return base_iterator(out, copy<Char>(begin, end, it));
+  }
+  auto sp = size_padding(num_digits, prefix, specs);
+  unsigned padding = sp.padding;
+  return write_padded<Char, align::right>(
+      out, specs, sp.size, [=](reserve_iterator<OutputIt> it) {
+        for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
+          *it++ = static_cast<Char>(p & 0xff);
+        it = detail::fill_n(it, padding, static_cast<Char>('0'));
+        return copy<Char>(begin, end, it);
+      });
 }
+
 template <typename Char, typename OutputIt, typename T>
 FMT_CONSTEXPR FMT_NOINLINE auto write_int_noinline(OutputIt out,
                                                    write_int_arg<T> arg,
-                                                   const format_specs& specs,
-                                                   locale_ref loc) -> OutputIt {
-  return write_int<Char>(out, arg, specs, loc);
+                                                   const format_specs& specs)
+    -> OutputIt {
+  return write_int<Char>(out, arg, specs);
 }
+
 template <typename Char, typename T,
           FMT_ENABLE_IF(is_integral<T>::value &&
                         !std::is_same<T, bool>::value &&
@@ -2209,10 +2137,11 @@ template <typename Char, typename T,
 FMT_CONSTEXPR FMT_INLINE auto write(basic_appender<Char> out, T value,
                                     const format_specs& specs, locale_ref loc)
     -> basic_appender<Char> {
-  if (specs.localized && write_loc(out, value, specs, loc)) return out;
-  return write_int_noinline<Char>(out, make_write_int_arg(value, specs.sign),
-                                  specs, loc);
+  if (specs.localized() && write_loc(out, value, specs, loc)) return out;
+  return write_int_noinline<Char>(out, make_write_int_arg(value, specs.sign()),
+                                  specs);
 }
+
 // An inlined version of write used in format string compilation.
 template <typename Char, typename OutputIt, typename T,
           FMT_ENABLE_IF(is_integral<T>::value &&
@@ -2222,85 +2151,138 @@ template <typename Char, typename OutputIt, typename T,
 FMT_CONSTEXPR FMT_INLINE auto write(OutputIt out, T value,
                                     const format_specs& specs, locale_ref loc)
     -> OutputIt {
-  if (specs.localized && write_loc(out, value, specs, loc)) return out;
-  return write_int<Char>(out, make_write_int_arg(value, specs.sign), specs,
-                         loc);
+  if (specs.localized() && write_loc(out, value, specs, loc)) return out;
+  return write_int<Char>(out, make_write_int_arg(value, specs.sign()), specs);
 }
 
-// An output iterator that counts the number of objects written to it and
-// discards them.
-class counting_iterator {
- private:
-  size_t count_;
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR auto write(OutputIt out, Char value, const format_specs& specs,
+                         locale_ref loc = {}) -> OutputIt {
+  // char is formatted as unsigned char for consistency across platforms.
+  using unsigned_type =
+      conditional_t<std::is_same<Char, char>::value, unsigned char, unsigned>;
+  return check_char_specs(specs)
+             ? write_char<Char>(out, value, specs)
+             : write<Char>(out, static_cast<unsigned_type>(value), specs, loc);
+}
 
- public:
-  using iterator_category = std::output_iterator_tag;
-  using difference_type = std::ptrdiff_t;
-  using pointer = void;
-  using reference = void;
-  FMT_UNCHECKED_ITERATOR(counting_iterator);
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(std::is_same<Char, char>::value)>
+FMT_CONSTEXPR auto write(OutputIt out, basic_string_view<Char> s,
+                         const format_specs& specs) -> OutputIt {
+  bool is_debug = specs.type() == presentation_type::debug;
+  if (specs.precision < 0 && specs.width == 0) {
+    auto&& it = reserve(out, s.size());
+    return is_debug ? write_escaped_string(it, s) : copy<char>(s, it);
+  }
+
+  size_t display_width_limit =
+      specs.precision < 0 ? SIZE_MAX : to_unsigned(specs.precision);
+  size_t display_width =
+      !is_debug || specs.precision == 0 ? 0 : 1;  // Account for opening '"'.
+  size_t size = !is_debug || specs.precision == 0 ? 0 : 1;
+  for_each_codepoint(s, [&](uint32_t cp, string_view sv) {
+    if (is_debug && needs_escape(cp)) {
+      counting_buffer<char> buf;
+      write_escaped_cp(basic_appender<char>(buf),
+                       find_escape_result<char>{sv.begin(), sv.end(), cp});
+      // We're reinterpreting bytes as display width. That's okay
+      // because write_escaped_cp() only writes ASCII characters.
+      size_t cp_width = buf.count();
+      if (display_width + cp_width <= display_width_limit) {
+        display_width += cp_width;
+        size += cp_width;
+        // If this is the end of the string, account for closing '"'.
+        if (display_width < display_width_limit && sv.end() == s.end()) {
+          ++display_width;
+          ++size;
+        }
+        return true;
+      }
 
-  struct value_type {
-    template <typename T> FMT_CONSTEXPR void operator=(const T&) {}
-  };
+      size += display_width_limit - display_width;
+      display_width = display_width_limit;
+      return false;
+    }
 
-  FMT_CONSTEXPR counting_iterator() : count_(0) {}
+    size_t cp_width = display_width_of(cp);
+    if (cp_width + display_width <= display_width_limit) {
+      display_width += cp_width;
+      size += sv.size();
+      // If this is the end of the string, account for closing '"'.
+      if (is_debug && display_width < display_width_limit &&
+          sv.end() == s.end()) {
+        ++display_width;
+        ++size;
+      }
+      return true;
+    }
 
-  FMT_CONSTEXPR auto count() const -> size_t { return count_; }
+    return false;
+  });
 
-  FMT_CONSTEXPR auto operator++() -> counting_iterator& {
-    ++count_;
-    return *this;
-  }
-  FMT_CONSTEXPR auto operator++(int) -> counting_iterator {
-    auto it = *this;
-    ++*this;
-    return it;
-  }
+  struct bounded_output_iterator {
+    reserve_iterator<OutputIt> underlying_iterator;
+    size_t bound;
 
-  FMT_CONSTEXPR friend auto operator+(counting_iterator it, difference_type n)
-      -> counting_iterator {
-    it.count_ += static_cast<size_t>(n);
-    return it;
-  }
+    FMT_CONSTEXPR auto operator*() -> bounded_output_iterator& { return *this; }
+    FMT_CONSTEXPR auto operator++() -> bounded_output_iterator& {
+      return *this;
+    }
+    FMT_CONSTEXPR auto operator++(int) -> bounded_output_iterator& {
+      return *this;
+    }
+    FMT_CONSTEXPR auto operator=(char c) -> bounded_output_iterator& {
+      if (bound > 0) {
+        *underlying_iterator++ = c;
+        --bound;
+      }
+      return *this;
+    }
+  };
 
-  FMT_CONSTEXPR auto operator*() const -> value_type { return {}; }
-};
+  return write_padded<char>(
+      out, specs, size, display_width, [=](reserve_iterator<OutputIt> it) {
+        return is_debug
+                   ? write_escaped_string(bounded_output_iterator{it, size}, s)
+                         .underlying_iterator
+                   : copy<char>(s.data(), s.data() + size, it);
+      });
+}
 
-template <typename Char, typename OutputIt>
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
 FMT_CONSTEXPR auto write(OutputIt out, basic_string_view<Char> s,
                          const format_specs& specs) -> OutputIt {
   auto data = s.data();
   auto size = s.size();
   if (specs.precision >= 0 && to_unsigned(specs.precision) < size)
-    size = code_point_index(s, to_unsigned(specs.precision));
-  bool is_debug = specs.type == presentation_type::debug;
-  size_t width = 0;
-
-  if (is_debug) size = write_escaped_string(counting_iterator{}, s).count();
+    size = to_unsigned(specs.precision);
 
-  if (specs.width != 0) {
-    if (is_debug)
-      width = size;
-    else
-      width = compute_width(basic_string_view<Char>(data, size));
+  bool is_debug = specs.type() == presentation_type::debug;
+  if (is_debug) {
+    auto buf = counting_buffer<Char>();
+    write_escaped_string(basic_appender<Char>(buf), s);
+    size = buf.count();
   }
-  return write_padded<Char>(out, specs, size, width,
-                            [=](reserve_iterator<OutputIt> it) {
-                              if (is_debug) return write_escaped_string(it, s);
-                              return copy<Char>(data, data + size, it);
-                            });
+
+  return write_padded<Char>(
+      out, specs, size, [=](reserve_iterator<OutputIt> it) {
+        return is_debug ? write_escaped_string(it, s)
+                        : copy<Char>(data, data + size, it);
+      });
 }
+
 template <typename Char, typename OutputIt>
-FMT_CONSTEXPR auto write(OutputIt out,
-                         basic_string_view<type_identity_t<Char>> s,
+FMT_CONSTEXPR auto write(OutputIt out, basic_string_view<Char> s,
                          const format_specs& specs, locale_ref) -> OutputIt {
   return write<Char>(out, s, specs);
 }
+
 template <typename Char, typename OutputIt>
 FMT_CONSTEXPR auto write(OutputIt out, const Char* s, const format_specs& specs,
                          locale_ref) -> OutputIt {
-  if (specs.type == presentation_type::pointer)
+  if (specs.type() == presentation_type::pointer)
     return write_ptr<Char>(out, bit_cast<uintptr_t>(s), &specs);
   if (!s) report_error("string pointer is null");
   return write<Char>(out, basic_string_view<Char>(s), specs, {});
@@ -2317,38 +2299,29 @@ FMT_CONSTEXPR auto write(OutputIt out, T value) -> OutputIt {
   if (negative) abs_value = ~abs_value + 1;
   int num_digits = count_digits(abs_value);
   auto size = (negative ? 1 : 0) + static_cast<size_t>(num_digits);
-  auto it = reserve(out, size);
-  if (auto ptr = to_pointer<Char>(it, size)) {
+  if (auto ptr = to_pointer<Char>(out, size)) {
     if (negative) *ptr++ = static_cast<Char>('-');
     format_decimal<Char>(ptr, abs_value, num_digits);
     return out;
   }
-  if (negative) *it++ = static_cast<Char>('-');
-  it = format_decimal<Char>(it, abs_value, num_digits).end;
-  return base_iterator(out, it);
+  if (negative) *out++ = static_cast<Char>('-');
+  return format_decimal<Char>(out, abs_value, num_digits);
 }
 
-// DEPRECATED!
 template <typename Char>
 FMT_CONSTEXPR auto parse_align(const Char* begin, const Char* end,
                                format_specs& specs) -> const Char* {
   FMT_ASSERT(begin != end, "");
-  auto align = align::none;
+  auto alignment = align::none;
   auto p = begin + code_point_length(begin);
   if (end - p <= 0) p = begin;
   for (;;) {
     switch (to_ascii(*p)) {
-    case '<':
-      align = align::left;
-      break;
-    case '>':
-      align = align::right;
-      break;
-    case '^':
-      align = align::center;
-      break;
+    case '<': alignment = align::left; break;
+    case '>': alignment = align::right; break;
+    case '^': alignment = align::center; break;
     }
-    if (align != align::none) {
+    if (alignment != align::none) {
       if (p != begin) {
         auto c = *begin;
         if (c == '}') return begin;
@@ -2356,7 +2329,7 @@ FMT_CONSTEXPR auto parse_align(const Char* begin, const Char* end,
           report_error("invalid fill character '{'");
           return begin;
         }
-        specs.fill = basic_string_view<Char>(begin, to_unsigned(p - begin));
+        specs.set_fill(basic_string_view<Char>(begin, to_unsigned(p - begin)));
         begin = p + 1;
       } else {
         ++begin;
@@ -2367,68 +2340,25 @@ FMT_CONSTEXPR auto parse_align(const Char* begin, const Char* end,
     }
     p = begin;
   }
-  specs.align = align;
+  specs.set_align(alignment);
   return begin;
 }
 
-// A floating-point presentation format.
-enum class float_format : unsigned char {
-  general,  // General: exponent notation or fixed point based on magnitude.
-  exp,      // Exponent notation with the default precision of 6, e.g. 1.2e-3.
-  fixed     // Fixed point with the default precision of 6, e.g. 0.0012.
-};
-
-struct float_specs {
-  int precision;
-  float_format format : 8;
-  sign_t sign : 8;
-  bool locale : 1;
-  bool binary32 : 1;
-  bool showpoint : 1;
-};
-
-// DEPRECATED!
-FMT_CONSTEXPR inline auto parse_float_type_spec(const format_specs& specs)
-    -> float_specs {
-  auto result = float_specs();
-  result.showpoint = specs.alt;
-  result.locale = specs.localized;
-  switch (specs.type) {
-  default:
-    FMT_FALLTHROUGH;
-  case presentation_type::none:
-    result.format = float_format::general;
-    break;
-  case presentation_type::exp:
-    result.format = float_format::exp;
-    result.showpoint |= specs.precision != 0;
-    break;
-  case presentation_type::fixed:
-    result.format = float_format::fixed;
-    result.showpoint |= specs.precision != 0;
-    break;
-  case presentation_type::general:
-    result.format = float_format::general;
-    break;
-  }
-  return result;
-}
-
 template <typename Char, typename OutputIt>
 FMT_CONSTEXPR20 auto write_nonfinite(OutputIt out, bool isnan,
-                                     format_specs specs, sign_t sign)
-    -> OutputIt {
+                                     format_specs specs, sign s) -> OutputIt {
   auto str =
-      isnan ? (specs.upper ? "NAN" : "nan") : (specs.upper ? "INF" : "inf");
+      isnan ? (specs.upper() ? "NAN" : "nan") : (specs.upper() ? "INF" : "inf");
   constexpr size_t str_size = 3;
-  auto size = str_size + (sign ? 1 : 0);
+  auto size = str_size + (s != sign::none ? 1 : 0);
   // Replace '0'-padding with space for non-finite values.
   const bool is_zero_fill =
-      specs.fill.size() == 1 && specs.fill.template get<Char>() == '0';
-  if (is_zero_fill) specs.fill = ' ';
+      specs.fill_size() == 1 && specs.fill_unit<Char>() == '0';
+  if (is_zero_fill) specs.set_fill(' ');
   return write_padded<Char>(out, specs, size,
                             [=](reserve_iterator<OutputIt> it) {
-                              if (sign) *it++ = detail::sign<Char>(sign);
+                              if (s != sign::none)
+                                *it++ = detail::getsign<Char>(s);
                               return copy<Char>(str, str + str_size, it);
                             });
 }
@@ -2456,7 +2386,7 @@ constexpr auto write_significand(OutputIt out, const char* significand,
 template <typename Char, typename OutputIt, typename UInt>
 inline auto write_significand(OutputIt out, UInt significand,
                               int significand_size) -> OutputIt {
-  return format_decimal<Char>(out, significand, significand_size).end;
+  return format_decimal<Char>(out, significand, significand_size);
 }
 template <typename Char, typename OutputIt, typename T, typename Grouping>
 FMT_CONSTEXPR20 auto write_significand(OutputIt out, T significand,
@@ -2476,14 +2406,13 @@ template <typename Char, typename UInt,
           FMT_ENABLE_IF(std::is_integral<UInt>::value)>
 inline auto write_significand(Char* out, UInt significand, int significand_size,
                               int integral_size, Char decimal_point) -> Char* {
-  if (!decimal_point)
-    return format_decimal(out, significand, significand_size).end;
+  if (!decimal_point) return format_decimal(out, significand, significand_size);
   out += significand_size + 1;
   Char* end = out;
   int floating_size = significand_size - integral_size;
   for (int i = floating_size / 2; i > 0; --i) {
     out -= 2;
-    copy2(out, digits2(static_cast<std::size_t>(significand % 100)));
+    write2digits(out, static_cast<size_t>(significand % 100));
     significand /= 100;
   }
   if (floating_size % 2 != 0) {
@@ -2537,111 +2466,18 @@ FMT_CONSTEXPR20 auto write_significand(OutputIt out, T significand,
                                      buffer.end(), out);
 }
 
-template <typename Char, typename OutputIt, typename DecimalFP,
-          typename Grouping = digit_grouping<Char>>
-FMT_CONSTEXPR20 auto do_write_float(OutputIt out, const DecimalFP& f,
-                                    const format_specs& specs,
-                                    float_specs fspecs, locale_ref loc)
-    -> OutputIt {
-  auto significand = f.significand;
-  int significand_size = get_significand_size(f);
-  const Char zero = static_cast<Char>('0');
-  auto sign = fspecs.sign;
-  size_t size = to_unsigned(significand_size) + (sign ? 1 : 0);
-  using iterator = reserve_iterator<OutputIt>;
-
-  Char decimal_point =
-      fspecs.locale ? detail::decimal_point<Char>(loc) : static_cast<Char>('.');
-
-  int output_exp = f.exponent + significand_size - 1;
-  auto use_exp_format = [=]() {
-    if (fspecs.format == float_format::exp) return true;
-    if (fspecs.format != float_format::general) return false;
-    // Use the fixed notation if the exponent is in [exp_lower, exp_upper),
-    // e.g. 0.0001 instead of 1e-04. Otherwise use the exponent notation.
-    const int exp_lower = -4, exp_upper = 16;
-    return output_exp < exp_lower ||
-           output_exp >= (fspecs.precision > 0 ? fspecs.precision : exp_upper);
-  };
-  if (use_exp_format()) {
-    int num_zeros = 0;
-    if (fspecs.showpoint) {
-      num_zeros = fspecs.precision - significand_size;
-      if (num_zeros < 0) num_zeros = 0;
-      size += to_unsigned(num_zeros);
-    } else if (significand_size == 1) {
-      decimal_point = Char();
-    }
-    auto abs_output_exp = output_exp >= 0 ? output_exp : -output_exp;
-    int exp_digits = 2;
-    if (abs_output_exp >= 100) exp_digits = abs_output_exp >= 1000 ? 4 : 3;
-
-    size += to_unsigned((decimal_point ? 1 : 0) + 2 + exp_digits);
-    char exp_char = specs.upper ? 'E' : 'e';
-    auto write = [=](iterator it) {
-      if (sign) *it++ = detail::sign<Char>(sign);
-      // Insert a decimal point after the first digit and add an exponent.
-      it = write_significand(it, significand, significand_size, 1,
-                             decimal_point);
-      if (num_zeros > 0) it = detail::fill_n(it, num_zeros, zero);
-      *it++ = static_cast<Char>(exp_char);
-      return write_exponent<Char>(output_exp, it);
-    };
-    return specs.width > 0
-               ? write_padded<Char, align::right>(out, specs, size, write)
-               : base_iterator(out, write(reserve(out, size)));
-  }
+// Numbers with exponents greater or equal to the returned value will use
+// the exponential notation.
+template <typename T> FMT_CONSTEVAL auto exp_upper() -> int {
+  return std::numeric_limits<T>::digits10 != 0
+             ? min_of(16, std::numeric_limits<T>::digits10 + 1)
+             : 16;
+}
 
-  int exp = f.exponent + significand_size;
-  if (f.exponent >= 0) {
-    // 1234e5 -> 123400000[.0+]
-    size += to_unsigned(f.exponent);
-    int num_zeros = fspecs.precision - exp;
-    abort_fuzzing_if(num_zeros > 5000);
-    if (fspecs.showpoint) {
-      ++size;
-      if (num_zeros <= 0 && fspecs.format != float_format::fixed) num_zeros = 0;
-      if (num_zeros > 0) size += to_unsigned(num_zeros);
-    }
-    auto grouping = Grouping(loc, fspecs.locale);
-    size += to_unsigned(grouping.count_separators(exp));
-    return write_padded<Char, align::right>(out, specs, size, [&](iterator it) {
-      if (sign) *it++ = detail::sign<Char>(sign);
-      it = write_significand<Char>(it, significand, significand_size,
-                                   f.exponent, grouping);
-      if (!fspecs.showpoint) return it;
-      *it++ = decimal_point;
-      return num_zeros > 0 ? detail::fill_n(it, num_zeros, zero) : it;
-    });
-  } else if (exp > 0) {
-    // 1234e-2 -> 12.34[0+]
-    int num_zeros = fspecs.showpoint ? fspecs.precision - significand_size : 0;
-    size += 1 + to_unsigned(num_zeros > 0 ? num_zeros : 0);
-    auto grouping = Grouping(loc, fspecs.locale);
-    size += to_unsigned(grouping.count_separators(exp));
-    return write_padded<Char, align::right>(out, specs, size, [&](iterator it) {
-      if (sign) *it++ = detail::sign<Char>(sign);
-      it = write_significand(it, significand, significand_size, exp,
-                             decimal_point, grouping);
-      return num_zeros > 0 ? detail::fill_n(it, num_zeros, zero) : it;
-    });
-  }
-  // 1234e-6 -> 0.001234
-  int num_zeros = -exp;
-  if (significand_size == 0 && fspecs.precision >= 0 &&
-      fspecs.precision < num_zeros) {
-    num_zeros = fspecs.precision;
-  }
-  bool pointy = num_zeros != 0 || significand_size != 0 || fspecs.showpoint;
-  size += 1 + (pointy ? 1 : 0) + to_unsigned(num_zeros);
-  return write_padded<Char, align::right>(out, specs, size, [&](iterator it) {
-    if (sign) *it++ = detail::sign<Char>(sign);
-    *it++ = zero;
-    if (!pointy) return it;
-    *it++ = decimal_point;
-    it = detail::fill_n(it, num_zeros, zero);
-    return write_significand<Char>(it, significand, significand_size);
-  });
+// Use the fixed notation if the exponent is in [-4, exp_upper),
+// e.g. 0.0001 instead of 1e-04. Otherwise use the exponent notation.
+constexpr auto use_fixed(int exp, int exp_upper) -> bool {
+  return exp >= -4 && exp < exp_upper;
 }
 
 template <typename Char> class fallback_digit_grouping {
@@ -2658,16 +2494,122 @@ template <typename Char> class fallback_digit_grouping {
   }
 };
 
+template <typename Char, typename Grouping, typename OutputIt,
+          typename DecimalFP>
+FMT_CONSTEXPR20 auto write_fixed(OutputIt out, const DecimalFP& f,
+                                 int significand_size, Char decimal_point,
+                                 const format_specs& specs, sign s,
+                                 locale_ref loc = {}) -> OutputIt {
+  using iterator = reserve_iterator<OutputIt>;
+
+  int exp = f.exponent + significand_size;
+  long long size = significand_size + (s != sign::none ? 1 : 0);
+  if (f.exponent >= 0) {
+    // 1234e5 -> 123400000[.0+]
+    size += f.exponent;
+    int num_zeros = specs.precision - exp;
+    abort_fuzzing_if(num_zeros > 5000);
+    if (specs.alt()) {
+      ++size;
+      if (num_zeros <= 0 && specs.type() != presentation_type::fixed)
+        num_zeros = 0;
+      if (num_zeros > 0) size += num_zeros;
+    }
+    auto grouping = Grouping(loc, specs.localized());
+    size += grouping.count_separators(exp);
+    return write_padded<Char, align::right>(
+        out, specs, static_cast<size_t>(size), [&](iterator it) {
+          if (s != sign::none) *it++ = detail::getsign<Char>(s);
+          it = write_significand<Char>(it, f.significand, significand_size,
+                                       f.exponent, grouping);
+          if (!specs.alt()) return it;
+          *it++ = decimal_point;
+          return num_zeros > 0 ? detail::fill_n(it, num_zeros, Char('0')) : it;
+        });
+  }
+  if (exp > 0) {
+    // 1234e-2 -> 12.34[0+]
+    int num_zeros = specs.alt() ? specs.precision - significand_size : 0;
+    size += 1 + max_of(num_zeros, 0);
+    auto grouping = Grouping(loc, specs.localized());
+    size += grouping.count_separators(exp);
+    return write_padded<Char, align::right>(
+        out, specs, to_unsigned(size), [&](iterator it) {
+          if (s != sign::none) *it++ = detail::getsign<Char>(s);
+          it = write_significand(it, f.significand, significand_size, exp,
+                                 decimal_point, grouping);
+          return num_zeros > 0 ? detail::fill_n(it, num_zeros, Char('0')) : it;
+        });
+  }
+  // 1234e-6 -> 0.001234
+  int num_zeros = -exp;
+  if (significand_size == 0 && specs.precision >= 0 &&
+      specs.precision < num_zeros) {
+    num_zeros = specs.precision;
+  }
+  bool pointy = num_zeros != 0 || significand_size != 0 || specs.alt();
+  size += 1 + (pointy ? 1 : 0) + num_zeros;
+  return write_padded<Char, align::right>(
+      out, specs, to_unsigned(size), [&](iterator it) {
+        if (s != sign::none) *it++ = detail::getsign<Char>(s);
+        *it++ = Char('0');
+        if (!pointy) return it;
+        *it++ = decimal_point;
+        it = detail::fill_n(it, num_zeros, Char('0'));
+        return write_significand<Char>(it, f.significand, significand_size);
+      });
+}
+
+template <typename Char, typename Grouping, typename OutputIt,
+          typename DecimalFP>
+FMT_CONSTEXPR20 auto do_write_float(OutputIt out, const DecimalFP& f,
+                                    const format_specs& specs, sign s,
+                                    int exp_upper, locale_ref loc) -> OutputIt {
+  Char point = specs.localized() ? detail::decimal_point<Char>(loc) : Char('.');
+  int significand_size = get_significand_size(f);
+  int exp = f.exponent + significand_size - 1;
+  if (specs.type() == presentation_type::fixed ||
+      (specs.type() != presentation_type::exp &&
+       use_fixed(exp, specs.precision > 0 ? specs.precision : exp_upper))) {
+    return write_fixed<Char, Grouping>(out, f, significand_size, point, specs,
+                                       s, loc);
+  }
+
+  // Write value in the exponential format.
+  int num_zeros = 0;
+  long long size = significand_size + (s != sign::none ? 1 : 0);
+  if (specs.alt()) {
+    num_zeros = max_of(specs.precision - significand_size, 0);
+    size += num_zeros;
+  } else if (significand_size == 1) {
+    point = Char();
+  }
+  size += (point ? 1 : 0) + compute_exp_size(exp);
+  char exp_char = specs.upper() ? 'E' : 'e';
+  auto write = [=](reserve_iterator<OutputIt> it) {
+    if (s != sign::none) *it++ = detail::getsign<Char>(s);
+    // Insert a decimal point after the first digit and add an exponent.
+    it = write_significand(it, f.significand, significand_size, 1, point);
+    if (num_zeros > 0) it = detail::fill_n(it, num_zeros, Char('0'));
+    *it++ = Char(exp_char);
+    return write_exponent<Char>(exp, it);
+  };
+  auto usize = to_unsigned(size);
+  return specs.width > 0
+             ? write_padded<Char, align::right>(out, specs, usize, write)
+             : base_iterator(out, write(reserve(out, usize)));
+}
+
 template <typename Char, typename OutputIt, typename DecimalFP>
 FMT_CONSTEXPR20 auto write_float(OutputIt out, const DecimalFP& f,
-                                 const format_specs& specs, float_specs fspecs,
-                                 locale_ref loc) -> OutputIt {
+                                 const format_specs& specs, sign s,
+                                 int exp_upper, locale_ref loc) -> OutputIt {
   if (is_constant_evaluated()) {
-    return do_write_float<Char, OutputIt, DecimalFP,
-                          fallback_digit_grouping<Char>>(out, f, specs, fspecs,
-                                                         loc);
+    return do_write_float<Char, fallback_digit_grouping<Char>>(out, f, specs, s,
+                                                               exp_upper, loc);
   } else {
-    return do_write_float<Char>(out, f, specs, fspecs, loc);
+    return do_write_float<Char, digit_grouping<Char>>(out, f, specs, s,
+                                                      exp_upper, loc);
   }
 }
 
@@ -2682,8 +2624,8 @@ template <typename T>
 struct has_isfinite<T, enable_if_t<sizeof(std::isfinite(T())) != 0>>
     : std::true_type {};
 
-template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value&&
-                                        has_isfinite<T>::value)>
+template <typename T,
+          FMT_ENABLE_IF(is_floating_point<T>::value&& has_isfinite<T>::value)>
 FMT_CONSTEXPR20 auto isfinite(T value) -> bool {
   constexpr T inf = T(std::numeric_limits<double>::infinity());
   if (is_constant_evaluated())
@@ -2698,7 +2640,7 @@ FMT_CONSTEXPR auto isfinite(T value) -> bool {
 }
 
 template <typename T, FMT_ENABLE_IF(is_floating_point<T>::value)>
-FMT_INLINE FMT_CONSTEXPR bool signbit(T value) {
+FMT_INLINE FMT_CONSTEXPR auto signbit(T value) -> bool {
   if (is_constant_evaluated()) {
 #ifdef __cpp_if_constexpr
     if constexpr (std::numeric_limits<double>::is_iec559) {
@@ -2720,52 +2662,48 @@ inline FMT_CONSTEXPR20 void adjust_precision(int& precision, int exp10) {
 
 class bigint {
  private:
-  // A bigint is stored as an array of bigits (big digits), with bigit at index
-  // 0 being the least significant one.
-  using bigit = uint32_t;
+  // A bigint is a number in the form bigit_[N - 1] ... bigit_[0] * 32^exp_.
+  using bigit = uint32_t;  // A big digit.
   using double_bigit = uint64_t;
+  enum { bigit_bits = num_bits<bigit>() };
   enum { bigits_capacity = 32 };
   basic_memory_buffer<bigit, bigits_capacity> bigits_;
   int exp_;
 
-  FMT_CONSTEXPR20 auto operator[](int index) const -> bigit {
-    return bigits_[to_unsigned(index)];
-  }
-  FMT_CONSTEXPR20 auto operator[](int index) -> bigit& {
-    return bigits_[to_unsigned(index)];
-  }
-
-  static constexpr const int bigit_bits = num_bits<bigit>();
-
   friend struct formatter<bigint>;
 
-  FMT_CONSTEXPR20 void subtract_bigits(int index, bigit other, bigit& borrow) {
-    auto result = static_cast<double_bigit>((*this)[index]) - other - borrow;
-    (*this)[index] = static_cast<bigit>(result);
+  FMT_CONSTEXPR auto get_bigit(int i) const -> bigit {
+    return i >= exp_ && i < num_bigits() ? bigits_[i - exp_] : 0;
+  }
+
+  FMT_CONSTEXPR void subtract_bigits(int index, bigit other, bigit& borrow) {
+    auto result = double_bigit(bigits_[index]) - other - borrow;
+    bigits_[index] = static_cast<bigit>(result);
     borrow = static_cast<bigit>(result >> (bigit_bits * 2 - 1));
   }
 
-  FMT_CONSTEXPR20 void remove_leading_zeros() {
+  FMT_CONSTEXPR void remove_leading_zeros() {
     int num_bigits = static_cast<int>(bigits_.size()) - 1;
-    while (num_bigits > 0 && (*this)[num_bigits] == 0) --num_bigits;
+    while (num_bigits > 0 && bigits_[num_bigits] == 0) --num_bigits;
     bigits_.resize(to_unsigned(num_bigits + 1));
   }
 
   // Computes *this -= other assuming aligned bigints and *this >= other.
-  FMT_CONSTEXPR20 void subtract_aligned(const bigint& other) {
+  FMT_CONSTEXPR void subtract_aligned(const bigint& other) {
     FMT_ASSERT(other.exp_ >= exp_, "unaligned bigints");
     FMT_ASSERT(compare(*this, other) >= 0, "");
     bigit borrow = 0;
     int i = other.exp_ - exp_;
     for (size_t j = 0, n = other.bigits_.size(); j != n; ++i, ++j)
       subtract_bigits(i, other.bigits_[j], borrow);
-    while (borrow > 0) subtract_bigits(i, 0, borrow);
+    if (borrow != 0) subtract_bigits(i, 0, borrow);
+    FMT_ASSERT(borrow == 0, "");
     remove_leading_zeros();
   }
 
-  FMT_CONSTEXPR20 void multiply(uint32_t value) {
-    const double_bigit wide_value = value;
+  FMT_CONSTEXPR void multiply(uint32_t value) {
     bigit carry = 0;
+    const double_bigit wide_value = value;
     for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
       double_bigit result = bigits_[i] * wide_value + carry;
       bigits_[i] = static_cast<bigit>(result);
@@ -2776,7 +2714,7 @@ class bigint {
 
   template <typename UInt, FMT_ENABLE_IF(std::is_same<UInt, uint64_t>::value ||
                                          std::is_same<UInt, uint128_t>::value)>
-  FMT_CONSTEXPR20 void multiply(UInt value) {
+  FMT_CONSTEXPR void multiply(UInt value) {
     using half_uint =
         conditional_t<std::is_same<UInt, uint128_t>::value, uint64_t, uint32_t>;
     const int shift = num_bits<half_uint>() - bigit_bits;
@@ -2797,7 +2735,7 @@ class bigint {
 
   template <typename UInt, FMT_ENABLE_IF(std::is_same<UInt, uint64_t>::value ||
                                          std::is_same<UInt, uint128_t>::value)>
-  FMT_CONSTEXPR20 void assign(UInt n) {
+  FMT_CONSTEXPR void assign(UInt n) {
     size_t num_bigits = 0;
     do {
       bigits_[num_bigits++] = static_cast<bigit>(n);
@@ -2808,13 +2746,13 @@ class bigint {
   }
 
  public:
-  FMT_CONSTEXPR20 bigint() : exp_(0) {}
+  FMT_CONSTEXPR bigint() : exp_(0) {}
   explicit bigint(uint64_t n) { assign(n); }
 
   bigint(const bigint&) = delete;
   void operator=(const bigint&) = delete;
 
-  FMT_CONSTEXPR20 void assign(const bigint& other) {
+  FMT_CONSTEXPR void assign(const bigint& other) {
     auto size = other.bigits_.size();
     bigits_.resize(size);
     auto data = other.bigits_.data();
@@ -2822,16 +2760,16 @@ class bigint {
     exp_ = other.exp_;
   }
 
-  template <typename Int> FMT_CONSTEXPR20 void operator=(Int n) {
+  template <typename Int> FMT_CONSTEXPR void operator=(Int n) {
     FMT_ASSERT(n > 0, "");
     assign(uint64_or_128_t<Int>(n));
   }
 
-  FMT_CONSTEXPR20 auto num_bigits() const -> int {
+  FMT_CONSTEXPR auto num_bigits() const -> int {
     return static_cast<int>(bigits_.size()) + exp_;
   }
 
-  FMT_NOINLINE FMT_CONSTEXPR20 auto operator<<=(int shift) -> bigint& {
+  FMT_CONSTEXPR auto operator<<=(int shift) -> bigint& {
     FMT_ASSERT(shift >= 0, "");
     exp_ += shift / bigit_bits;
     shift %= bigit_bits;
@@ -2846,49 +2784,39 @@ class bigint {
     return *this;
   }
 
-  template <typename Int>
-  FMT_CONSTEXPR20 auto operator*=(Int value) -> bigint& {
+  template <typename Int> FMT_CONSTEXPR auto operator*=(Int value) -> bigint& {
     FMT_ASSERT(value > 0, "");
     multiply(uint32_or_64_or_128_t<Int>(value));
     return *this;
   }
 
-  friend FMT_CONSTEXPR20 auto compare(const bigint& lhs, const bigint& rhs)
-      -> int {
-    int num_lhs_bigits = lhs.num_bigits(), num_rhs_bigits = rhs.num_bigits();
-    if (num_lhs_bigits != num_rhs_bigits)
-      return num_lhs_bigits > num_rhs_bigits ? 1 : -1;
-    int i = static_cast<int>(lhs.bigits_.size()) - 1;
-    int j = static_cast<int>(rhs.bigits_.size()) - 1;
+  friend FMT_CONSTEXPR auto compare(const bigint& b1, const bigint& b2) -> int {
+    int num_bigits1 = b1.num_bigits(), num_bigits2 = b2.num_bigits();
+    if (num_bigits1 != num_bigits2) return num_bigits1 > num_bigits2 ? 1 : -1;
+    int i = static_cast<int>(b1.bigits_.size()) - 1;
+    int j = static_cast<int>(b2.bigits_.size()) - 1;
     int end = i - j;
     if (end < 0) end = 0;
     for (; i >= end; --i, --j) {
-      bigit lhs_bigit = lhs[i], rhs_bigit = rhs[j];
-      if (lhs_bigit != rhs_bigit) return lhs_bigit > rhs_bigit ? 1 : -1;
+      bigit b1_bigit = b1.bigits_[i], b2_bigit = b2.bigits_[j];
+      if (b1_bigit != b2_bigit) return b1_bigit > b2_bigit ? 1 : -1;
     }
     if (i != j) return i > j ? 1 : -1;
     return 0;
   }
 
   // Returns compare(lhs1 + lhs2, rhs).
-  friend FMT_CONSTEXPR20 auto add_compare(const bigint& lhs1,
-                                          const bigint& lhs2, const bigint& rhs)
-      -> int {
-    auto minimum = [](int a, int b) { return a < b ? a : b; };
-    auto maximum = [](int a, int b) { return a > b ? a : b; };
-    int max_lhs_bigits = maximum(lhs1.num_bigits(), lhs2.num_bigits());
+  friend FMT_CONSTEXPR auto add_compare(const bigint& lhs1, const bigint& lhs2,
+                                        const bigint& rhs) -> int {
+    int max_lhs_bigits = max_of(lhs1.num_bigits(), lhs2.num_bigits());
     int num_rhs_bigits = rhs.num_bigits();
     if (max_lhs_bigits + 1 < num_rhs_bigits) return -1;
     if (max_lhs_bigits > num_rhs_bigits) return 1;
-    auto get_bigit = [](const bigint& n, int i) -> bigit {
-      return i >= n.exp_ && i < n.num_bigits() ? n[i - n.exp_] : 0;
-    };
     double_bigit borrow = 0;
-    int min_exp = minimum(minimum(lhs1.exp_, lhs2.exp_), rhs.exp_);
+    int min_exp = min_of(min_of(lhs1.exp_, lhs2.exp_), rhs.exp_);
     for (int i = num_rhs_bigits - 1; i >= min_exp; --i) {
-      double_bigit sum =
-          static_cast<double_bigit>(get_bigit(lhs1, i)) + get_bigit(lhs2, i);
-      bigit rhs_bigit = get_bigit(rhs, i);
+      double_bigit sum = double_bigit(lhs1.get_bigit(i)) + lhs2.get_bigit(i);
+      bigit rhs_bigit = rhs.get_bigit(i);
       if (sum > rhs_bigit + borrow) return 1;
       borrow = rhs_bigit + borrow - sum;
       if (borrow > 1) return -1;
@@ -2901,10 +2829,8 @@ class bigint {
   FMT_CONSTEXPR20 void assign_pow10(int exp) {
     FMT_ASSERT(exp >= 0, "");
     if (exp == 0) return *this = 1;
-    // Find the top bit.
-    int bitmask = 1;
-    while (exp >= bitmask) bitmask <<= 1;
-    bitmask >>= 1;
+    int bitmask = 1 << (num_bits<unsigned>() -
+                        countl_zero(static_cast<uint32_t>(exp)) - 1);
     // pow(10, exp) = pow(5, exp) * pow(2, exp). First compute pow(5, exp) by
     // repeated squaring and multiplication.
     *this = 5;
@@ -2928,17 +2854,17 @@ class bigint {
       // cross-product terms n[i] * n[j] such that i + j == bigit_index.
       for (int i = 0, j = bigit_index; j >= 0; ++i, --j) {
         // Most terms are multiplied twice which can be optimized in the future.
-        sum += static_cast<double_bigit>(n[i]) * n[j];
+        sum += double_bigit(n[i]) * n[j];
       }
-      (*this)[bigit_index] = static_cast<bigit>(sum);
+      bigits_[bigit_index] = static_cast<bigit>(sum);
       sum >>= num_bits<bigit>();  // Compute the carry.
     }
     // Do the same for the top half.
     for (int bigit_index = num_bigits; bigit_index < num_result_bigits;
          ++bigit_index) {
       for (int j = num_bigits - 1, i = bigit_index - j; i < num_bigits;)
-        sum += static_cast<double_bigit>(n[i++]) * n[j--];
-      (*this)[bigit_index] = static_cast<bigit>(sum);
+        sum += double_bigit(n[i++]) * n[j--];
+      bigits_[bigit_index] = static_cast<bigit>(sum);
       sum >>= num_bits<bigit>();
     }
     remove_leading_zeros();
@@ -2947,20 +2873,20 @@ class bigint {
 
   // If this bigint has a bigger exponent than other, adds trailing zero to make
   // exponents equal. This simplifies some operations such as subtraction.
-  FMT_CONSTEXPR20 void align(const bigint& other) {
+  FMT_CONSTEXPR void align(const bigint& other) {
     int exp_difference = exp_ - other.exp_;
     if (exp_difference <= 0) return;
     int num_bigits = static_cast<int>(bigits_.size());
     bigits_.resize(to_unsigned(num_bigits + exp_difference));
     for (int i = num_bigits - 1, j = i + exp_difference; i >= 0; --i, --j)
       bigits_[j] = bigits_[i];
-    memset(bigits_.data(), 0, to_unsigned(exp_difference) * sizeof(bigit));
+    fill_n(bigits_.data(), to_unsigned(exp_difference), 0U);
     exp_ -= exp_difference;
   }
 
   // Divides this bignum by divisor, assigning the remainder to this and
   // returning the quotient.
-  FMT_CONSTEXPR20 auto divmod_assign(const bigint& divisor) -> int {
+  FMT_CONSTEXPR auto divmod_assign(const bigint& divisor) -> int {
     FMT_ASSERT(this != &divisor, "");
     if (compare(*this, divisor) < 0) return 0;
     FMT_ASSERT(divisor.bigits_[divisor.bigits_.size() - 1u] != 0, "");
@@ -3131,18 +3057,17 @@ FMT_CONSTEXPR20 void format_hexfloat(Float value, format_specs specs,
   // Assume Float is in the format [sign][exponent][significand].
   using carrier_uint = typename info::carrier_uint;
 
-  constexpr auto num_float_significand_bits =
-      detail::num_significand_bits<Float>();
+  const auto num_float_significand_bits = detail::num_significand_bits<Float>();
 
   basic_fp<carrier_uint> f(value);
   f.e += num_float_significand_bits;
   if (!has_implicit_bit<Float>()) --f.e;
 
-  constexpr auto num_fraction_bits =
+  const auto num_fraction_bits =
       num_float_significand_bits + (has_implicit_bit<Float>() ? 1 : 0);
-  constexpr auto num_xdigits = (num_fraction_bits + 3) / 4;
+  const auto num_xdigits = (num_fraction_bits + 3) / 4;
 
-  constexpr auto leading_shift = ((num_xdigits - 1) * 4);
+  const auto leading_shift = ((num_xdigits - 1) * 4);
   const auto leading_mask = carrier_uint(0xF) << leading_shift;
   const auto leading_xdigit =
       static_cast<uint32_t>((f.f & leading_mask) >> leading_shift);
@@ -3174,20 +3099,20 @@ FMT_CONSTEXPR20 void format_hexfloat(Float value, format_specs specs,
 
   char xdigits[num_bits<carrier_uint>() / 4];
   detail::fill_n(xdigits, sizeof(xdigits), '0');
-  format_uint<4>(xdigits, f.f, num_xdigits, specs.upper);
+  format_base2e(4, xdigits, f.f, num_xdigits, specs.upper());
 
   // Remove zero tail
   while (print_xdigits > 0 && xdigits[print_xdigits] == '0') --print_xdigits;
 
   buf.push_back('0');
-  buf.push_back(specs.upper ? 'X' : 'x');
+  buf.push_back(specs.upper() ? 'X' : 'x');
   buf.push_back(xdigits[0]);
-  if (specs.alt || print_xdigits > 0 || print_xdigits < specs.precision)
+  if (specs.alt() || print_xdigits > 0 || print_xdigits < specs.precision)
     buf.push_back('.');
   buf.append(xdigits + 1, xdigits + 1 + print_xdigits);
   for (; print_xdigits < specs.precision; ++print_xdigits) buf.push_back('0');
 
-  buf.push_back(specs.upper ? 'P' : 'p');
+  buf.push_back(specs.upper() ? 'P' : 'p');
 
   uint32_t abs_e;
   if (f.e < 0) {
@@ -3218,15 +3143,15 @@ constexpr auto fractional_part_rounding_thresholds(int index) -> uint32_t {
 }
 
 template <typename Float>
-FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
+FMT_CONSTEXPR20 auto format_float(Float value, int precision,
+                                  const format_specs& specs, bool binary32,
                                   buffer<char>& buf) -> int {
   // float is passed as double to reduce the number of instantiations.
   static_assert(!std::is_same<Float, float>::value, "");
-  FMT_ASSERT(value >= 0, "value is negative");
   auto converted_value = convert_float(value);
 
-  const bool fixed = specs.format == float_format::fixed;
-  if (value <= 0) {  // <= instead of == to silence a warning.
+  const bool fixed = specs.type() == presentation_type::fixed;
+  if (value == 0) {
     if (precision <= 0 || !fixed) {
       buf.push_back('0');
       return 0;
@@ -3251,16 +3176,6 @@ FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
     exp = static_cast<int>(e);
     if (e > exp) ++exp;  // Compute ceil.
     dragon_flags = dragon::fixup;
-  } else if (precision < 0) {
-    // Use Dragonbox for the shortest format.
-    if (specs.binary32) {
-      auto dec = dragonbox::to_decimal(static_cast<float>(value));
-      write<char>(appender(buf), dec.significand);
-      return dec.exponent;
-    }
-    auto dec = dragonbox::to_decimal(static_cast<double>(value));
-    write<char>(appender(buf), dec.significand);
-    return dec.exponent;
   } else {
     // Extract significand bits and exponent bits.
     using info = dragonbox::float_info<double>;
@@ -3359,7 +3274,7 @@ FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
         uint64_t prod;
         uint32_t digits;
         bool should_round_up;
-        int number_of_digits_to_print = precision > 9 ? 9 : precision;
+        int number_of_digits_to_print = min_of(precision, 9);
 
         // Print a 9-digits subsegment, either the first or the second.
         auto print_subsegment = [&](uint32_t subsegment, char* buffer) {
@@ -3387,7 +3302,7 @@ FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
             // for details.
             prod = ((subsegment * static_cast<uint64_t>(450359963)) >> 20) + 1;
             digits = static_cast<uint32_t>(prod >> 32);
-            copy2(buffer, digits2(digits));
+            write2digits(buffer, digits);
             number_of_digits_printed += 2;
           }
 
@@ -3395,7 +3310,7 @@ FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
           while (number_of_digits_printed < number_of_digits_to_print) {
             prod = static_cast<uint32_t>(prod) * static_cast<uint64_t>(100);
             digits = static_cast<uint32_t>(prod >> 32);
-            copy2(buffer + number_of_digits_printed, digits2(digits));
+            write2digits(buffer + number_of_digits_printed, digits);
             number_of_digits_printed += 2;
           }
         };
@@ -3504,9 +3419,8 @@ FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
   }
   if (use_dragon) {
     auto f = basic_fp<uint128_t>();
-    bool is_predecessor_closer = specs.binary32
-                                     ? f.assign(static_cast<float>(value))
-                                     : f.assign(converted_value);
+    bool is_predecessor_closer = binary32 ? f.assign(static_cast<float>(value))
+                                          : f.assign(converted_value);
     if (is_predecessor_closer) dragon_flags |= dragon::predecessor_closer;
     if (fixed) dragon_flags |= dragon::fixed;
     // Limit precision to the maximum possible number of significant digits in
@@ -3515,7 +3429,7 @@ FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
     if (precision > max_double_digits) precision = max_double_digits;
     format_dragon(f, dragon_flags, precision, buf, exp);
   }
-  if (!fixed && !specs.showpoint) {
+  if (!fixed && !specs.alt()) {
     // Remove trailing zeros.
     auto num_digits = buf.size();
     while (num_digits > 0 && buf[num_digits - 1] == '0') {
@@ -3527,96 +3441,134 @@ FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
   return exp;
 }
 
-template <typename Char, typename OutputIt, typename T>
-FMT_CONSTEXPR20 auto write_float(OutputIt out, T value, format_specs specs,
-                                 locale_ref loc) -> OutputIt {
-  sign_t sign = specs.sign;
-  if (detail::signbit(value)) {  // value < 0 is false for NaN so use signbit.
-    sign = sign::minus;
-    value = -value;
-  } else if (sign == sign::minus) {
-    sign = sign::none;
-  }
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_floating_point<T>::value)>
+FMT_CONSTEXPR20 auto write(OutputIt out, T value, format_specs specs,
+                           locale_ref loc = {}) -> OutputIt {
+  if (specs.localized() && write_loc(out, value, specs, loc)) return out;
+
+  // Use signbit because value < 0 is false for NaN.
+  sign s = detail::signbit(value) ? sign::minus : specs.sign();
 
   if (!detail::isfinite(value))
-    return write_nonfinite<Char>(out, detail::isnan(value), specs, sign);
+    return write_nonfinite<Char>(out, detail::isnan(value), specs, s);
 
-  if (specs.align == align::numeric && sign) {
-    auto it = reserve(out, 1);
-    *it++ = detail::sign<Char>(sign);
-    out = base_iterator(out, it);
-    sign = sign::none;
+  if (specs.align() == align::numeric && s != sign::none) {
+    *out++ = detail::getsign<Char>(s);
+    s = sign::none;
     if (specs.width != 0) --specs.width;
   }
 
+  const int exp_upper = detail::exp_upper<T>();
+  int precision = specs.precision;
+  if (precision < 0) {
+    if (specs.type() != presentation_type::none) {
+      precision = 6;
+    } else if (is_fast_float<T>::value && !is_constant_evaluated()) {
+      // Use Dragonbox for the shortest format.
+      auto dec = dragonbox::to_decimal(static_cast<fast_float_t<T>>(value));
+      return write_float<Char>(out, dec, specs, s, exp_upper, loc);
+    }
+  }
+
   memory_buffer buffer;
-  if (specs.type == presentation_type::hexfloat) {
-    if (sign) buffer.push_back(detail::sign<char>(sign));
+  if (specs.type() == presentation_type::hexfloat) {
+    if (s != sign::none) buffer.push_back(detail::getsign<char>(s));
     format_hexfloat(convert_float(value), specs, buffer);
     return write_bytes<Char, align::right>(out, {buffer.data(), buffer.size()},
                                            specs);
   }
 
-  int precision = specs.precision >= 0 || specs.type == presentation_type::none
-                      ? specs.precision
-                      : 6;
-  if (specs.type == presentation_type::exp) {
+  if (specs.type() == presentation_type::exp) {
     if (precision == max_value<int>())
       report_error("number is too big");
     else
       ++precision;
-  } else if (specs.type != presentation_type::fixed && precision == 0) {
+    if (specs.precision != 0) specs.set_alt();
+  } else if (specs.type() == presentation_type::fixed) {
+    if (specs.precision != 0) specs.set_alt();
+  } else if (precision == 0) {
     precision = 1;
   }
-  float_specs fspecs = parse_float_type_spec(specs);
-  fspecs.sign = sign;
-  if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
-  int exp = format_float(convert_float(value), precision, fspecs, buffer);
-  fspecs.precision = precision;
-  auto f = big_decimal_fp{buffer.data(), static_cast<int>(buffer.size()), exp};
-  return write_float<Char>(out, f, specs, fspecs, loc);
-}
+  int exp = format_float(convert_float(value), precision, specs,
+                         std::is_same<T, float>(), buffer);
 
-template <typename Char, typename OutputIt, typename T,
-          FMT_ENABLE_IF(is_floating_point<T>::value)>
-FMT_CONSTEXPR20 auto write(OutputIt out, T value, format_specs specs,
-                           locale_ref loc = {}) -> OutputIt {
-  if (const_check(!is_supported_floating_point(value))) return out;
-  return specs.localized && write_loc(out, value, specs, loc)
-             ? out
-             : write_float<Char>(out, value, specs, loc);
+  specs.precision = precision;
+  auto f = big_decimal_fp{buffer.data(), static_cast<int>(buffer.size()), exp};
+  return write_float<Char>(out, f, specs, s, exp_upper, loc);
 }
 
 template <typename Char, typename OutputIt, typename T,
           FMT_ENABLE_IF(is_fast_float<T>::value)>
 FMT_CONSTEXPR20 auto write(OutputIt out, T value) -> OutputIt {
   if (is_constant_evaluated()) return write<Char>(out, value, format_specs());
-  if (const_check(!is_supported_floating_point(value))) return out;
 
-  auto sign = sign_t::none;
-  if (detail::signbit(value)) {
-    sign = sign::minus;
-    value = -value;
+  auto s = detail::signbit(value) ? sign::minus : sign::none;
+  auto mask = exponent_mask<fast_float_t<T>>();
+  if ((bit_cast<decltype(mask)>(value) & mask) == mask)
+    return write_nonfinite<Char>(out, std::isnan(value), {}, s);
+
+  auto dec = dragonbox::to_decimal(static_cast<fast_float_t<T>>(value));
+  auto significand = dec.significand;
+  int significand_size = count_digits(significand);
+  int exponent = dec.exponent + significand_size - 1;
+  if (use_fixed(exponent, detail::exp_upper<T>())) {
+    return write_fixed<Char, fallback_digit_grouping<Char>>(
+        out, dec, significand_size, Char('.'), {}, s);
+  }
+
+  // Write value in the exponential format.
+  const char* prefix = "e+";
+  int abs_exponent = exponent;
+  if (exponent < 0) {
+    abs_exponent = -exponent;
+    prefix = "e-";
+  }
+  auto has_decimal_point = significand_size != 1;
+  size_t size = std::is_pointer<OutputIt>::value
+                    ? 0u
+                    : to_unsigned((s != sign::none ? 1 : 0) + significand_size +
+                                  (has_decimal_point ? 1 : 0) +
+                                  (abs_exponent >= 100 ? 5 : 4));
+  if (auto ptr = to_pointer<Char>(out, size)) {
+    if (s != sign::none) *ptr++ = Char('-');
+    if (has_decimal_point) {
+      auto begin = ptr;
+      ptr = format_decimal<Char>(ptr, significand, significand_size + 1);
+      *begin = begin[1];
+      begin[1] = '.';
+    } else {
+      *ptr++ = static_cast<Char>('0' + significand);
+    }
+    if (std::is_same<Char, char>::value) {
+      memcpy(ptr, prefix, 2);
+      ptr += 2;
+    } else {
+      *ptr++ = prefix[0];
+      *ptr++ = prefix[1];
+    }
+    if (abs_exponent >= 100) {
+      *ptr++ = static_cast<Char>('0' + abs_exponent / 100);
+      abs_exponent %= 100;
+    }
+    write2digits(ptr, static_cast<unsigned>(abs_exponent));
+    return select<std::is_pointer<OutputIt>::value>(ptr + 2, out);
   }
-
-  constexpr auto specs = format_specs();
-  using floaty = conditional_t<std::is_same<T, long double>::value, double, T>;
-  using floaty_uint = typename dragonbox::float_info<floaty>::carrier_uint;
-  floaty_uint mask = exponent_mask<floaty>();
-  if ((bit_cast<floaty_uint>(value) & mask) == mask)
-    return write_nonfinite<Char>(out, std::isnan(value), specs, sign);
-
-  auto fspecs = float_specs();
-  fspecs.sign = sign;
-  auto dec = dragonbox::to_decimal(static_cast<floaty>(value));
-  return write_float<Char>(out, dec, specs, fspecs, {});
+  auto it = reserve(out, size);
+  if (s != sign::none) *it++ = Char('-');
+  // Insert a decimal point after the first digit and add an exponent.
+  it = write_significand(it, significand, significand_size, 1,
+                         has_decimal_point ? Char('.') : Char());
+  *it++ = Char('e');
+  it = write_exponent<Char>(exponent, it);
+  return base_iterator(out, it);
 }
 
 template <typename Char, typename OutputIt, typename T,
           FMT_ENABLE_IF(is_floating_point<T>::value &&
                         !is_fast_float<T>::value)>
 inline auto write(OutputIt out, T value) -> OutputIt {
-  return write<Char>(out, value, format_specs());
+  return write<Char>(out, value, {});
 }
 
 template <typename Char, typename OutputIt>
@@ -3629,9 +3581,7 @@ auto write(OutputIt out, monostate, format_specs = {}, locale_ref = {})
 template <typename Char, typename OutputIt>
 FMT_CONSTEXPR auto write(OutputIt out, basic_string_view<Char> value)
     -> OutputIt {
-  auto it = reserve(out, value.size());
-  it = copy_noinline<Char>(value.begin(), value.end(), it);
-  return base_iterator(out, it);
+  return copy_noinline<Char>(value.begin(), value.end(), out);
 }
 
 template <typename Char, typename OutputIt, typename T,
@@ -3643,10 +3593,8 @@ constexpr auto write(OutputIt out, const T& value) -> OutputIt {
 // FMT_ENABLE_IF() condition separated to workaround an MSVC bug.
 template <
     typename Char, typename OutputIt, typename T,
-    bool check =
-        std::is_enum<T>::value && !std::is_same<T, Char>::value &&
-        mapped_type_constant<T, basic_format_context<OutputIt, Char>>::value !=
-            type::custom_type,
+    bool check = std::is_enum<T>::value && !std::is_same<T, Char>::value &&
+                 mapped_type_constant<T, Char>::value != type::custom_type,
     FMT_ENABLE_IF(check)>
 FMT_CONSTEXPR auto write(OutputIt out, T value) -> OutputIt {
   return write<Char>(out, static_cast<underlying_t<T>>(value));
@@ -3656,8 +3604,8 @@ template <typename Char, typename OutputIt, typename T,
           FMT_ENABLE_IF(std::is_same<T, bool>::value)>
 FMT_CONSTEXPR auto write(OutputIt out, T value, const format_specs& specs = {},
                          locale_ref = {}) -> OutputIt {
-  return specs.type != presentation_type::none &&
-                 specs.type != presentation_type::string
+  return specs.type() != presentation_type::none &&
+                 specs.type() != presentation_type::string
              ? write<Char>(out, value ? 1 : 0, specs, {})
              : write_bytes<Char>(out, value ? "true" : "false", specs);
 }
@@ -3683,158 +3631,123 @@ auto write(OutputIt out, const T* value, const format_specs& specs = {},
   return write_ptr<Char>(out, bit_cast<uintptr_t>(value), &specs);
 }
 
-// A write overload that handles implicit conversions.
 template <typename Char, typename OutputIt, typename T,
-          typename Context = basic_format_context<OutputIt, Char>>
-FMT_CONSTEXPR auto write(OutputIt out, const T& value) -> enable_if_t<
-    std::is_class<T>::value && !has_to_string_view<T>::value &&
-        !is_floating_point<T>::value && !std::is_same<T, Char>::value &&
-        !std::is_same<T, remove_cvref_t<decltype(arg_mapper<Context>().map(
-                             value))>>::value,
-    OutputIt> {
-  return write<Char>(out, arg_mapper<Context>().map(value));
+          FMT_ENABLE_IF(mapped_type_constant<T, Char>::value ==
+                            type::custom_type &&
+                        !std::is_fundamental<T>::value)>
+FMT_CONSTEXPR auto write(OutputIt out, const T& value) -> OutputIt {
+  auto f = formatter<T, Char>();
+  auto parse_ctx = parse_context<Char>({});
+  f.parse(parse_ctx);
+  auto ctx = basic_format_context<OutputIt, Char>(out, {}, {});
+  return f.format(value, ctx);
 }
 
-template <typename Char, typename OutputIt, typename T,
-          typename Context = basic_format_context<OutputIt, Char>>
-FMT_CONSTEXPR auto write(OutputIt out, const T& value)
-    -> enable_if_t<mapped_type_constant<T, Context>::value ==
-                           type::custom_type &&
-                       !std::is_fundamental<T>::value,
-                   OutputIt> {
-  auto formatter = typename Context::template formatter_type<T>();
-  auto parse_ctx = typename Context::parse_context_type({});
-  formatter.parse(parse_ctx);
-  auto ctx = Context(out, {}, {});
-  return formatter.format(value, ctx);
-}
+template <typename T>
+using is_builtin =
+    bool_constant<std::is_same<T, int>::value || FMT_BUILTIN_TYPES>;
 
 // An argument visitor that formats the argument and writes it via the output
 // iterator. It's a class and not a generic lambda for compatibility with C++11.
 template <typename Char> struct default_arg_formatter {
-  using iterator = basic_appender<Char>;
   using context = buffered_context<Char>;
 
-  iterator out;
-  basic_format_args<context> args;
-  locale_ref loc;
+  basic_appender<Char> out;
+
+  void operator()(monostate) { report_error("argument not found"); }
+
+  template <typename T, FMT_ENABLE_IF(is_builtin<T>::value)>
+  void operator()(T value) {
+    write<Char>(out, value);
+  }
 
-  template <typename T> auto operator()(T value) -> iterator {
-    return write<Char>(out, value);
+  template <typename T, FMT_ENABLE_IF(!is_builtin<T>::value)>
+  void operator()(T) {
+    FMT_ASSERT(false, "");
   }
-  auto operator()(typename basic_format_arg<context>::handle h) -> iterator {
-    basic_format_parse_context<Char> parse_ctx({});
-    context format_ctx(out, args, loc);
+
+  void operator()(typename basic_format_arg<context>::handle h) {
+    // Use a null locale since the default format must be unlocalized.
+    auto parse_ctx = parse_context<Char>({});
+    auto format_ctx = context(out, {}, {});
     h.format(parse_ctx, format_ctx);
-    return format_ctx.out();
   }
 };
 
 template <typename Char> struct arg_formatter {
-  using iterator = basic_appender<Char>;
-  using context = buffered_context<Char>;
-
-  iterator out;
+  basic_appender<Char> out;
   const format_specs& specs;
-  locale_ref locale;
+  FMT_NO_UNIQUE_ADDRESS locale_ref locale;
 
-  template <typename T>
-  FMT_CONSTEXPR FMT_INLINE auto operator()(T value) -> iterator {
-    return detail::write<Char>(out, value, specs, locale);
+  template <typename T, FMT_ENABLE_IF(is_builtin<T>::value)>
+  FMT_CONSTEXPR FMT_INLINE void operator()(T value) {
+    detail::write<Char>(out, value, specs, locale);
   }
-  auto operator()(typename basic_format_arg<context>::handle) -> iterator {
-    // User-defined types are handled separately because they require access
-    // to the parse context.
-    return out;
-  }
-};
 
-struct width_checker {
-  template <typename T, FMT_ENABLE_IF(is_integer<T>::value)>
-  FMT_CONSTEXPR auto operator()(T value) -> unsigned long long {
-    if (is_negative(value)) report_error("negative width");
-    return static_cast<unsigned long long>(value);
+  template <typename T, FMT_ENABLE_IF(!is_builtin<T>::value)>
+  void operator()(T) {
+    FMT_ASSERT(false, "");
   }
 
-  template <typename T, FMT_ENABLE_IF(!is_integer<T>::value)>
-  FMT_CONSTEXPR auto operator()(T) -> unsigned long long {
-    report_error("width is not integer");
-    return 0;
+  void operator()(typename basic_format_arg<buffered_context<Char>>::handle) {
+    // User-defined types are handled separately because they require access
+    // to the parse context.
   }
 };
 
-struct precision_checker {
+struct dynamic_spec_getter {
   template <typename T, FMT_ENABLE_IF(is_integer<T>::value)>
   FMT_CONSTEXPR auto operator()(T value) -> unsigned long long {
-    if (is_negative(value)) report_error("negative precision");
-    return static_cast<unsigned long long>(value);
+    return is_negative(value) ? ~0ull : static_cast<unsigned long long>(value);
   }
 
   template <typename T, FMT_ENABLE_IF(!is_integer<T>::value)>
   FMT_CONSTEXPR auto operator()(T) -> unsigned long long {
-    report_error("precision is not integer");
+    report_error("width/precision is not integer");
     return 0;
   }
 };
 
-template <typename Handler, typename FormatArg>
-FMT_CONSTEXPR auto get_dynamic_spec(FormatArg arg) -> int {
-  unsigned long long value = arg.visit(Handler());
-  if (value > to_unsigned(max_value<int>())) report_error("number is too big");
-  return static_cast<int>(value);
-}
-
-template <typename Context, typename ID>
-FMT_CONSTEXPR auto get_arg(Context& ctx, ID id) -> decltype(ctx.arg(id)) {
-  auto arg = ctx.arg(id);
+template <typename Context>
+FMT_CONSTEXPR void handle_dynamic_spec(
+    arg_id_kind kind, int& value,
+    const arg_ref<typename Context::char_type>& ref, Context& ctx) {
+  if (kind == arg_id_kind::none) return;
+  auto arg =
+      kind == arg_id_kind::index ? ctx.arg(ref.index) : ctx.arg(ref.name);
   if (!arg) report_error("argument not found");
-  return arg;
-}
-
-template <typename Handler, typename Context>
-FMT_CONSTEXPR void handle_dynamic_spec(int& value,
-                                       arg_ref<typename Context::char_type> ref,
-                                       Context& ctx) {
-  switch (ref.kind) {
-  case arg_id_kind::none:
-    break;
-  case arg_id_kind::index:
-    value = detail::get_dynamic_spec<Handler>(get_arg(ctx, ref.val.index));
-    break;
-  case arg_id_kind::name:
-    value = detail::get_dynamic_spec<Handler>(get_arg(ctx, ref.val.name));
-    break;
-  }
+  unsigned long long result = arg.visit(dynamic_spec_getter());
+  if (result > to_unsigned(max_value<int>()))
+    report_error("width/precision is out of range");
+  value = static_cast<int>(result);
 }
 
-#if FMT_USE_USER_DEFINED_LITERALS
-#  if FMT_USE_NONTYPE_TEMPLATE_ARGS
+#if FMT_USE_NONTYPE_TEMPLATE_ARGS
 template <typename T, typename Char, size_t N,
-          fmt::detail_exported::fixed_string<Char, N> Str>
-struct statically_named_arg : view {
+          fmt::detail::fixed_string<Char, N> Str>
+struct static_named_arg : view {
   static constexpr auto name = Str.data;
 
   const T& value;
-  statically_named_arg(const T& v) : value(v) {}
+  static_named_arg(const T& v) : value(v) {}
 };
 
 template <typename T, typename Char, size_t N,
-          fmt::detail_exported::fixed_string<Char, N> Str>
-struct is_named_arg<statically_named_arg<T, Char, N, Str>> : std::true_type {};
+          fmt::detail::fixed_string<Char, N> Str>
+struct is_named_arg<static_named_arg<T, Char, N, Str>> : std::true_type {};
 
 template <typename T, typename Char, size_t N,
-          fmt::detail_exported::fixed_string<Char, N> Str>
-struct is_statically_named_arg<statically_named_arg<T, Char, N, Str>>
-    : std::true_type {};
+          fmt::detail::fixed_string<Char, N> Str>
+struct is_static_named_arg<static_named_arg<T, Char, N, Str>> : std::true_type {
+};
 
-template <typename Char, size_t N,
-          fmt::detail_exported::fixed_string<Char, N> Str>
+template <typename Char, size_t N, fmt::detail::fixed_string<Char, N> Str>
 struct udl_arg {
   template <typename T> auto operator=(T&& value) const {
-    return statically_named_arg<T, Char, N, Str>(std::forward<T>(value));
+    return static_named_arg<T, Char, N, Str>(std::forward<T>(value));
   }
 };
-#  else
+#else
 template <typename Char> struct udl_arg {
   const Char* str;
 
@@ -3842,145 +3755,175 @@ template <typename Char> struct udl_arg {
     return {str, std::forward<T>(value)};
   }
 };
-#  endif
-#endif  // FMT_USE_USER_DEFINED_LITERALS
-
-template <typename Locale, typename Char>
-auto vformat(const Locale& loc, basic_string_view<Char> fmt,
-             typename detail::vformat_args<Char>::type args)
-    -> std::basic_string<Char> {
-  auto buf = basic_memory_buffer<Char>();
-  detail::vformat_to(buf, fmt, args, detail::locale_ref(loc));
-  return {buf.data(), buf.size()};
-}
+#endif  // FMT_USE_NONTYPE_TEMPLATE_ARGS
+
+template <typename Char = char> struct format_handler {
+  parse_context<Char> parse_ctx;
+  buffered_context<Char> ctx;
+
+  void on_text(const Char* begin, const Char* end) {
+    copy_noinline<Char>(begin, end, ctx.out());
+  }
+
+  FMT_CONSTEXPR auto on_arg_id() -> int { return parse_ctx.next_arg_id(); }
+  FMT_CONSTEXPR auto on_arg_id(int id) -> int {
+    parse_ctx.check_arg_id(id);
+    return id;
+  }
+  FMT_CONSTEXPR auto on_arg_id(basic_string_view<Char> id) -> int {
+    parse_ctx.check_arg_id(id);
+    int arg_id = ctx.arg_id(id);
+    if (arg_id < 0) report_error("argument not found");
+    return arg_id;
+  }
+
+  FMT_INLINE void on_replacement_field(int id, const Char*) {
+    ctx.arg(id).visit(default_arg_formatter<Char>{ctx.out()});
+  }
+
+  auto on_format_specs(int id, const Char* begin, const Char* end)
+      -> const Char* {
+    auto arg = ctx.arg(id);
+    if (!arg) report_error("argument not found");
+    // Not using a visitor for custom types gives better codegen.
+    if (arg.format_custom(begin, parse_ctx, ctx)) return parse_ctx.begin();
+
+    auto specs = dynamic_format_specs<Char>();
+    begin = parse_format_specs(begin, end, specs, parse_ctx, arg.type());
+    if (specs.dynamic()) {
+      handle_dynamic_spec(specs.dynamic_width(), specs.width, specs.width_ref,
+                          ctx);
+      handle_dynamic_spec(specs.dynamic_precision(), specs.precision,
+                          specs.precision_ref, ctx);
+    }
 
+    arg.visit(arg_formatter<Char>{ctx.out(), specs, ctx.locale()});
+    return begin;
+  }
+
+  FMT_NORETURN void on_error(const char* message) { report_error(message); }
+};
+
+// It is used in format-inl.h and os.cc.
 using format_func = void (*)(detail::buffer<char>&, int, const char*);
+FMT_API void do_report_error(format_func func, int error_code,
+                             const char* message) noexcept;
 
 FMT_API void format_error_code(buffer<char>& out, int error_code,
                                string_view message) noexcept;
 
-using fmt::report_error;
-FMT_API void report_error(format_func func, int error_code,
-                          const char* message) noexcept;
+template <typename T, typename Char, type TYPE>
+template <typename FormatContext>
+FMT_CONSTEXPR auto native_formatter<T, Char, TYPE>::format(
+    const T& val, FormatContext& ctx) const -> decltype(ctx.out()) {
+  if (!specs_.dynamic())
+    return write<Char>(ctx.out(), val, specs_, ctx.locale());
+  auto specs = format_specs(specs_);
+  handle_dynamic_spec(specs.dynamic_width(), specs.width, specs_.width_ref,
+                      ctx);
+  handle_dynamic_spec(specs.dynamic_precision(), specs.precision,
+                      specs_.precision_ref, ctx);
+  return write<Char>(ctx.out(), val, specs, ctx.locale());
+}
 }  // namespace detail
 
 FMT_BEGIN_EXPORT
-FMT_API auto vsystem_error(int error_code, string_view format_str,
-                           format_args args) -> std::system_error;
 
-/**
- * Constructs `std::system_error` with a message formatted with
- * `fmt::format(fmt, args...)`.
- * `error_code` is a system error code as given by `errno`.
- *
- * **Example**:
- *
- *     // This throws std::system_error with the description
- *     //   cannot open file 'madeup': No such file or directory
- *     // or similar (system message may vary).
- *     const char* filename = "madeup";
- *     std::FILE* file = std::fopen(filename, "r");
- *     if (!file)
- *       throw fmt::system_error(errno, "cannot open file '{}'", filename);
- */
-template <typename... T>
-auto system_error(int error_code, format_string<T...> fmt, T&&... args)
-    -> std::system_error {
-  return vsystem_error(error_code, fmt, fmt::make_format_args(args...));
-}
+// A generic formatting context with custom output iterator and character
+// (code unit) support. Char is the format string code unit type which can be
+// different from OutputIt::value_type.
+template <typename OutputIt, typename Char> class generic_context {
+ private:
+  OutputIt out_;
+  basic_format_args<generic_context> args_;
+  locale_ref loc_;
 
-/**
- * Formats an error message for an error returned by an operating system or a
- * language runtime, for example a file opening error, and writes it to `out`.
- * The format is the same as the one used by `std::system_error(ec, message)`
- * where `ec` is `std::error_code(error_code, std::generic_category())`.
- * It is implementation-defined but normally looks like:
- *
- *     <message>: <system-message>
- *
- * where `<message>` is the passed message and `<system-message>` is the system
- * message corresponding to the error code.
- * `error_code` is a system error code as given by `errno`.
- */
-FMT_API void format_system_error(detail::buffer<char>& out, int error_code,
-                                 const char* message) noexcept;
+ public:
+  using char_type = Char;
+  using iterator = OutputIt;
+  enum { builtin_types = FMT_BUILTIN_TYPES };
 
-// Reports a system error without throwing an exception.
-// Can be used to report errors from destructors.
-FMT_API void report_system_error(int error_code, const char* message) noexcept;
+  constexpr generic_context(OutputIt out,
+                            basic_format_args<generic_context> args,
+                            locale_ref loc = {})
+      : out_(out), args_(args), loc_(loc) {}
+  generic_context(generic_context&&) = default;
+  generic_context(const generic_context&) = delete;
+  void operator=(const generic_context&) = delete;
 
-/// A fast integer formatter.
-class format_int {
- private:
-  // Buffer should be large enough to hold all digits (digits10 + 1),
-  // a sign and a null character.
-  enum { buffer_size = std::numeric_limits<unsigned long long>::digits10 + 3 };
-  mutable char buffer_[buffer_size];
-  char* str_;
-
-  template <typename UInt>
-  FMT_CONSTEXPR20 auto format_unsigned(UInt value) -> char* {
-    auto n = static_cast<detail::uint32_or_64_or_128_t<UInt>>(value);
-    return detail::format_decimal(buffer_, n, buffer_size - 1).begin;
+  constexpr auto arg(int id) const -> basic_format_arg<generic_context> {
+    return args_.get(id);
+  }
+  auto arg(basic_string_view<Char> name) const
+      -> basic_format_arg<generic_context> {
+    return args_.get(name);
+  }
+  constexpr auto arg_id(basic_string_view<Char> name) const -> int {
+    return args_.get_id(name);
   }
 
-  template <typename Int>
-  FMT_CONSTEXPR20 auto format_signed(Int value) -> char* {
-    auto abs_value = static_cast<detail::uint32_or_64_or_128_t<Int>>(value);
-    bool negative = value < 0;
-    if (negative) abs_value = 0 - abs_value;
-    auto begin = format_unsigned(abs_value);
-    if (negative) *--begin = '-';
-    return begin;
+  constexpr auto out() const -> iterator { return out_; }
+
+  void advance_to(iterator it) {
+    if (!detail::is_back_insert_iterator<iterator>()) out_ = it;
   }
 
+  constexpr auto locale() const -> locale_ref { return loc_; }
+};
+
+class loc_value {
+ private:
+  basic_format_arg<context> value_;
+
  public:
-  explicit FMT_CONSTEXPR20 format_int(int value) : str_(format_signed(value)) {}
-  explicit FMT_CONSTEXPR20 format_int(long value)
-      : str_(format_signed(value)) {}
-  explicit FMT_CONSTEXPR20 format_int(long long value)
-      : str_(format_signed(value)) {}
-  explicit FMT_CONSTEXPR20 format_int(unsigned value)
-      : str_(format_unsigned(value)) {}
-  explicit FMT_CONSTEXPR20 format_int(unsigned long value)
-      : str_(format_unsigned(value)) {}
-  explicit FMT_CONSTEXPR20 format_int(unsigned long long value)
-      : str_(format_unsigned(value)) {}
+  template <typename T, FMT_ENABLE_IF(!detail::is_float128<T>::value)>
+  loc_value(T value) : value_(value) {}
 
-  /// Returns the number of characters written to the output buffer.
-  FMT_CONSTEXPR20 auto size() const -> size_t {
-    return detail::to_unsigned(buffer_ - str_ + buffer_size - 1);
+  template <typename T, FMT_ENABLE_IF(detail::is_float128<T>::value)>
+  loc_value(T) {}
+
+  template <typename Visitor> auto visit(Visitor&& vis) -> decltype(vis(0)) {
+    return value_.visit(vis);
   }
+};
 
-  /// Returns a pointer to the output buffer content. No terminating null
-  /// character is appended.
-  FMT_CONSTEXPR20 auto data() const -> const char* { return str_; }
+// A locale facet that formats values in UTF-8.
+// It is parameterized on the locale to avoid the heavy <locale> include.
+template <typename Locale> class format_facet : public Locale::facet {
+ private:
+  std::string separator_;
+  std::string grouping_;
+  std::string decimal_point_;
 
-  /// Returns a pointer to the output buffer content with terminating null
-  /// character appended.
-  FMT_CONSTEXPR20 auto c_str() const -> const char* {
-    buffer_[buffer_size - 1] = '\0';
-    return str_;
-  }
+ protected:
+  virtual auto do_put(appender out, loc_value val,
+                      const format_specs& specs) const -> bool;
 
-  /// Returns the content of the output buffer as an `std::string`.
-  auto str() const -> std::string { return std::string(str_, size()); }
-};
+ public:
+  static FMT_API typename Locale::id id;
 
-template <typename T, typename Char>
-struct formatter<T, Char, enable_if_t<detail::has_format_as<T>::value>>
-    : formatter<detail::format_as_t<T>, Char> {
-  template <typename FormatContext>
-  auto format(const T& value, FormatContext& ctx) const -> decltype(ctx.out()) {
-    using base = formatter<detail::format_as_t<T>, Char>;
-    auto&& val = format_as(value);  // Make an lvalue reference for format.
-    return base::format(val, ctx);
+  explicit format_facet(Locale& loc);
+  explicit format_facet(string_view sep = "", std::string grouping = "\3",
+                        std::string decimal_point = ".")
+      : separator_(sep.data(), sep.size()),
+        grouping_(grouping),
+        decimal_point_(decimal_point) {}
+
+  auto put(appender out, loc_value val, const format_specs& specs) const
+      -> bool {
+    return do_put(out, val, specs);
   }
 };
 
-#define FMT_FORMAT_AS(Type, Base) \
-  template <typename Char>        \
-  struct formatter<Type, Char> : formatter<Base, Char> {}
+#define FMT_FORMAT_AS(Type, Base)                                   \
+  template <typename Char>                                          \
+  struct formatter<Type, Char> : formatter<Base, Char> {            \
+    template <typename FormatContext>                               \
+    FMT_CONSTEXPR auto format(Type value, FormatContext& ctx) const \
+        -> decltype(ctx.out()) {                                    \
+      return formatter<Base, Char>::format(value, ctx);             \
+    }                                                               \
+  }
 
 FMT_FORMAT_AS(signed char, int);
 FMT_FORMAT_AS(unsigned char, unsigned);
@@ -3989,16 +3932,38 @@ FMT_FORMAT_AS(unsigned short, unsigned);
 FMT_FORMAT_AS(long, detail::long_type);
 FMT_FORMAT_AS(unsigned long, detail::ulong_type);
 FMT_FORMAT_AS(Char*, const Char*);
-FMT_FORMAT_AS(std::nullptr_t, const void*);
 FMT_FORMAT_AS(detail::std_string_view<Char>, basic_string_view<Char>);
+FMT_FORMAT_AS(std::nullptr_t, const void*);
 FMT_FORMAT_AS(void*, const void*);
 
+template <typename Char, size_t N>
+struct formatter<Char[N], Char> : formatter<basic_string_view<Char>, Char> {};
+
 template <typename Char, typename Traits, typename Allocator>
 class formatter<std::basic_string<Char, Traits, Allocator>, Char>
     : public formatter<basic_string_view<Char>, Char> {};
 
-template <typename Char, size_t N>
-struct formatter<Char[N], Char> : formatter<basic_string_view<Char>, Char> {};
+template <int N, typename Char>
+struct formatter<detail::bitint<N>, Char> : formatter<long long, Char> {};
+template <int N, typename Char>
+struct formatter<detail::ubitint<N>, Char>
+    : formatter<unsigned long long, Char> {};
+
+template <typename Char>
+struct formatter<detail::float128, Char>
+    : detail::native_formatter<detail::float128, Char,
+                               detail::type::float_type> {};
+
+template <typename T, typename Char>
+struct formatter<T, Char, void_t<detail::format_as_result<T>>>
+    : formatter<detail::format_as_result<T>, Char> {
+  template <typename FormatContext>
+  FMT_CONSTEXPR auto format(const T& value, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    auto&& val = format_as(value);  // Make an lvalue reference for format.
+    return formatter<detail::format_as_result<T>, Char>::format(val, ctx);
+  }
+};
 
 /**
  * Converts `p` to `const void*` for pointer formatting.
@@ -4008,7 +3973,7 @@ struct formatter<Char[N], Char> : formatter<basic_string_view<Char>, Char> {};
  *     auto s = fmt::format("{}", fmt::ptr(p));
  */
 template <typename T> auto ptr(T p) -> const void* {
-  static_assert(std::is_pointer<T>::value, "");
+  static_assert(std::is_pointer<T>::value, "fmt::ptr used with non-pointer");
   return detail::bit_cast<const void*>(p);
 }
 
@@ -4018,7 +3983,7 @@ template <typename T> auto ptr(T p) -> const void* {
  * **Example**:
  *
  *     enum class color { red, green, blue };
- *     auto s = fmt::format("{}", fmt::underlying(color::red));
+ *     auto s = fmt::format("{}", fmt::underlying(color::red));  // s == "0"
  */
 template <typename Enum>
 constexpr auto underlying(Enum e) noexcept -> underlying_t<Enum> {
@@ -4032,13 +3997,23 @@ constexpr auto format_as(Enum e) noexcept -> underlying_t<Enum> {
 }
 }  // namespace enums
 
-class bytes {
- private:
-  string_view data_;
-  friend struct formatter<bytes>;
+#ifdef __cpp_lib_byte
+template <typename Char>
+struct formatter<std::byte, Char> : formatter<unsigned, Char> {
+  static auto format_as(std::byte b) -> unsigned char {
+    return static_cast<unsigned char>(b);
+  }
+  template <typename Context>
+  auto format(std::byte b, Context& ctx) const -> decltype(ctx.out()) {
+    return formatter<unsigned, Char>::format(format_as(b), ctx);
+  }
+};
+#endif
 
- public:
-  explicit bytes(string_view data) : data_(data) {}
+struct bytes {
+  string_view data;
+
+  inline explicit bytes(string_view s) : data(s) {}
 };
 
 template <> struct formatter<bytes> {
@@ -4046,8 +4021,7 @@ template <> struct formatter<bytes> {
   detail::dynamic_format_specs<> specs_;
 
  public:
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> const char* {
+  FMT_CONSTEXPR auto parse(parse_context<>& ctx) -> const char* {
     return parse_format_specs(ctx.begin(), ctx.end(), specs_, ctx,
                               detail::type::string_type);
   }
@@ -4055,11 +4029,11 @@ template <> struct formatter<bytes> {
   template <typename FormatContext>
   auto format(bytes b, FormatContext& ctx) const -> decltype(ctx.out()) {
     auto specs = specs_;
-    detail::handle_dynamic_spec<detail::width_checker>(specs.width,
-                                                       specs.width_ref, ctx);
-    detail::handle_dynamic_spec<detail::precision_checker>(
-        specs.precision, specs.precision_ref, ctx);
-    return detail::write_bytes<char>(ctx.out(), b.data_, specs);
+    detail::handle_dynamic_spec(specs.dynamic_width(), specs.width,
+                                specs.width_ref, ctx);
+    detail::handle_dynamic_spec(specs.dynamic_precision(), specs.precision,
+                                specs.precision_ref, ctx);
+    return detail::write_bytes<char>(ctx.out(), b.data, specs);
   }
 };
 
@@ -4086,21 +4060,20 @@ template <typename T> struct formatter<group_digits_view<T>> : formatter<T> {
   detail::dynamic_format_specs<> specs_;
 
  public:
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> const char* {
+  FMT_CONSTEXPR auto parse(parse_context<>& ctx) -> const char* {
     return parse_format_specs(ctx.begin(), ctx.end(), specs_, ctx,
                               detail::type::int_type);
   }
 
   template <typename FormatContext>
-  auto format(group_digits_view<T> t, FormatContext& ctx) const
+  auto format(group_digits_view<T> view, FormatContext& ctx) const
       -> decltype(ctx.out()) {
     auto specs = specs_;
-    detail::handle_dynamic_spec<detail::width_checker>(specs.width,
-                                                       specs.width_ref, ctx);
-    detail::handle_dynamic_spec<detail::precision_checker>(
-        specs.precision, specs.precision_ref, ctx);
-    auto arg = detail::make_write_int_arg(t.value, specs.sign);
+    detail::handle_dynamic_spec(specs.dynamic_width(), specs.width,
+                                specs.width_ref, ctx);
+    detail::handle_dynamic_spec(specs.dynamic_precision(), specs.precision,
+                                specs.precision_ref, ctx);
+    auto arg = detail::make_write_int_arg(view.value, specs.sign());
     return detail::write_int(
         ctx.out(), static_cast<detail::uint64_or_128_t<T>>(arg.abs_value),
         arg.prefix, specs, detail::digit_grouping<char>("\3", ","));
@@ -4114,8 +4087,7 @@ template <typename T, typename Char> struct nested_view {
 
 template <typename T, typename Char>
 struct formatter<nested_view<T, Char>, Char> {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     return ctx.begin();
   }
   template <typename FormatContext>
@@ -4127,22 +4099,25 @@ struct formatter<nested_view<T, Char>, Char> {
 
 template <typename T, typename Char = char> struct nested_formatter {
  private:
+  basic_specs specs_;
   int width_;
-  detail::fill_t fill_;
-  align_t align_ : 4;
   formatter<T, Char> formatter_;
 
  public:
-  constexpr nested_formatter() : width_(0), align_(align_t::none) {}
-
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
-    auto specs = detail::dynamic_format_specs<Char>();
-    auto it = parse_format_specs(ctx.begin(), ctx.end(), specs, ctx,
-                                 detail::type::none_type);
-    width_ = specs.width;
-    fill_ = specs.fill;
-    align_ = specs.align;
+  constexpr nested_formatter() : width_(0) {}
+
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+    auto it = ctx.begin(), end = ctx.end();
+    if (it == end) return it;
+    auto specs = format_specs();
+    it = detail::parse_align(it, end, specs);
+    specs_ = specs;
+    Char c = *it;
+    auto width_ref = detail::arg_ref<Char>();
+    if ((c >= '0' && c <= '9') || c == '{') {
+      it = detail::parse_width(it, end, specs, width_ref, ctx);
+      width_ = specs.width;
+    }
     ctx.advance_to(it);
     return formatter_.parse(ctx);
   }
@@ -4154,8 +4129,8 @@ template <typename T, typename Char = char> struct nested_formatter {
     write(basic_appender<Char>(buf));
     auto specs = format_specs();
     specs.width = width_;
-    specs.fill = fill_;
-    specs.align = align_;
+    specs.copy_fill_from(specs_);
+    specs.set_align(specs_.align());
     return detail::write<Char>(
         ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
   }
@@ -4165,180 +4140,197 @@ template <typename T, typename Char = char> struct nested_formatter {
   }
 };
 
+inline namespace literals {
+#if FMT_USE_NONTYPE_TEMPLATE_ARGS
+template <detail::fixed_string S> constexpr auto operator""_a() {
+  using char_t = remove_cvref_t<decltype(*S.data)>;
+  return detail::udl_arg<char_t, sizeof(S.data) / sizeof(char_t), S>();
+}
+#else
 /**
- * Converts `value` to `std::string` using the default format for type `T`.
+ * User-defined literal equivalent of `fmt::arg`.
  *
  * **Example**:
  *
- *     std::string answer = fmt::to_string(42);
+ *     using namespace fmt::literals;
+ *     fmt::print("The answer is {answer}.", "answer"_a=42);
  */
-template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value &&
-                                    !detail::has_format_as<T>::value)>
-inline auto to_string(const T& value) -> std::string {
-  auto buffer = memory_buffer();
-  detail::write<char>(appender(buffer), value);
-  return {buffer.data(), buffer.size()};
-}
-
-template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-FMT_NODISCARD inline auto to_string(T value) -> std::string {
-  // The buffer should be large enough to store the number including the sign
-  // or "false" for bool.
-  constexpr int max_size = detail::digits10<T>() + 2;
-  char buffer[max_size > 5 ? static_cast<unsigned>(max_size) : 5];
-  char* begin = buffer;
-  return std::string(begin, detail::write<char>(begin, value));
+constexpr auto operator""_a(const char* s, size_t) -> detail::udl_arg<char> {
+  return {s};
 }
+#endif  // FMT_USE_NONTYPE_TEMPLATE_ARGS
+}  // namespace literals
 
-template <typename Char, size_t SIZE>
-FMT_NODISCARD auto to_string(const basic_memory_buffer<Char, SIZE>& buf)
-    -> std::basic_string<Char> {
-  auto size = buf.size();
-  detail::assume(size < std::basic_string<Char>().max_size());
-  return std::basic_string<Char>(buf.data(), size);
-}
+/// A fast integer formatter.
+class format_int {
+ private:
+  // Buffer should be large enough to hold all digits (digits10 + 1),
+  // a sign and a null character.
+  enum { buffer_size = std::numeric_limits<unsigned long long>::digits10 + 3 };
+  mutable char buffer_[buffer_size];
+  char* str_;
 
-template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value &&
-                                    detail::has_format_as<T>::value)>
-inline auto to_string(const T& value) -> std::string {
-  return to_string(format_as(value));
-}
+  template <typename UInt>
+  FMT_CONSTEXPR20 auto format_unsigned(UInt value) -> char* {
+    auto n = static_cast<detail::uint32_or_64_or_128_t<UInt>>(value);
+    return detail::do_format_decimal(buffer_, n, buffer_size - 1);
+  }
 
-FMT_END_EXPORT
+  template <typename Int>
+  FMT_CONSTEXPR20 auto format_signed(Int value) -> char* {
+    auto abs_value = static_cast<detail::uint32_or_64_or_128_t<Int>>(value);
+    bool negative = value < 0;
+    if (negative) abs_value = 0 - abs_value;
+    auto begin = format_unsigned(abs_value);
+    if (negative) *--begin = '-';
+    return begin;
+  }
 
-namespace detail {
+ public:
+  FMT_CONSTEXPR20 explicit format_int(int value) : str_(format_signed(value)) {}
+  FMT_CONSTEXPR20 explicit format_int(long value)
+      : str_(format_signed(value)) {}
+  FMT_CONSTEXPR20 explicit format_int(long long value)
+      : str_(format_signed(value)) {}
+  FMT_CONSTEXPR20 explicit format_int(unsigned value)
+      : str_(format_unsigned(value)) {}
+  FMT_CONSTEXPR20 explicit format_int(unsigned long value)
+      : str_(format_unsigned(value)) {}
+  FMT_CONSTEXPR20 explicit format_int(unsigned long long value)
+      : str_(format_unsigned(value)) {}
 
-template <typename Char>
-void vformat_to(buffer<Char>& buf, basic_string_view<Char> fmt,
-                typename vformat_args<Char>::type args, locale_ref loc) {
-  auto out = basic_appender<Char>(buf);
-  if (fmt.size() == 2 && equal2(fmt.data(), "{}")) {
-    auto arg = args.get(0);
-    if (!arg) report_error("argument not found");
-    arg.visit(default_arg_formatter<Char>{out, args, loc});
-    return;
+  /// Returns the number of characters written to the output buffer.
+  FMT_CONSTEXPR20 auto size() const -> size_t {
+    return detail::to_unsigned(buffer_ - str_ + buffer_size - 1);
   }
 
-  struct format_handler {
-    basic_format_parse_context<Char> parse_context;
-    buffered_context<Char> context;
+  /// Returns a pointer to the output buffer content. No terminating null
+  /// character is appended.
+  FMT_CONSTEXPR20 auto data() const -> const char* { return str_; }
 
-    format_handler(basic_appender<Char> p_out, basic_string_view<Char> str,
-                   basic_format_args<buffered_context<Char>> p_args,
-                   locale_ref p_loc)
-        : parse_context(str), context(p_out, p_args, p_loc) {}
+  /// Returns a pointer to the output buffer content with terminating null
+  /// character appended.
+  FMT_CONSTEXPR20 auto c_str() const -> const char* {
+    buffer_[buffer_size - 1] = '\0';
+    return str_;
+  }
 
-    void on_text(const Char* begin, const Char* end) {
-      auto text = basic_string_view<Char>(begin, to_unsigned(end - begin));
-      context.advance_to(write<Char>(context.out(), text));
-    }
+  /// Returns the content of the output buffer as an `std::string`.
+  inline auto str() const -> std::string { return {str_, size()}; }
+};
 
-    FMT_CONSTEXPR auto on_arg_id() -> int {
-      return parse_context.next_arg_id();
-    }
-    FMT_CONSTEXPR auto on_arg_id(int id) -> int {
-      parse_context.check_arg_id(id);
-      return id;
-    }
-    FMT_CONSTEXPR auto on_arg_id(basic_string_view<Char> id) -> int {
-      parse_context.check_arg_id(id);
-      int arg_id = context.arg_id(id);
-      if (arg_id < 0) report_error("argument not found");
-      return arg_id;
-    }
+#if FMT_CLANG_ANALYZER
+#  define FMT_STRING_IMPL(s, base) s
+#else
+#  define FMT_STRING_IMPL(s, base)                                           \
+    [] {                                                                     \
+      /* Use the hidden visibility as a workaround for a GCC bug (#1973). */ \
+      /* Use a macro-like name to avoid shadowing warnings. */               \
+      struct FMT_VISIBILITY("hidden") FMT_COMPILE_STRING : base {            \
+        using char_type = fmt::remove_cvref_t<decltype(s[0])>;               \
+        constexpr explicit operator fmt::basic_string_view<char_type>()      \
+            const {                                                          \
+          return fmt::detail::compile_string_to_view<char_type>(s);          \
+        }                                                                    \
+      };                                                                     \
+      using FMT_STRING_VIEW =                                                \
+          fmt::basic_string_view<typename FMT_COMPILE_STRING::char_type>;    \
+      fmt::detail::ignore_unused(FMT_STRING_VIEW(FMT_COMPILE_STRING()));     \
+      return FMT_COMPILE_STRING();                                           \
+    }()
+#endif  // FMT_CLANG_ANALYZER
 
-    FMT_INLINE void on_replacement_field(int id, const Char*) {
-      auto arg = get_arg(context, id);
-      context.advance_to(arg.visit(default_arg_formatter<Char>{
-          context.out(), context.args(), context.locale()}));
-    }
+/**
+ * Constructs a legacy compile-time format string from a string literal `s`.
+ *
+ * **Example**:
+ *
+ *     // A compile-time error because 'd' is an invalid specifier for strings.
+ *     std::string s = fmt::format(FMT_STRING("{:d}"), "foo");
+ */
+#define FMT_STRING(s) FMT_STRING_IMPL(s, fmt::detail::compile_string)
 
-    auto on_format_specs(int id, const Char* begin, const Char* end)
-        -> const Char* {
-      auto arg = get_arg(context, id);
-      // Not using a visitor for custom types gives better codegen.
-      if (arg.format_custom(begin, parse_context, context))
-        return parse_context.begin();
-      auto specs = detail::dynamic_format_specs<Char>();
-      begin = parse_format_specs(begin, end, specs, parse_context, arg.type());
-      detail::handle_dynamic_spec<detail::width_checker>(
-          specs.width, specs.width_ref, context);
-      detail::handle_dynamic_spec<detail::precision_checker>(
-          specs.precision, specs.precision_ref, context);
-      if (begin == end || *begin != '}')
-        report_error("missing '}' in format string");
-      context.advance_to(arg.visit(
-          arg_formatter<Char>{context.out(), specs, context.locale()}));
-      return begin;
-    }
+FMT_API auto vsystem_error(int error_code, string_view fmt, format_args args)
+    -> std::system_error;
 
-    FMT_NORETURN void on_error(const char* message) { report_error(message); }
-  };
-  detail::parse_format_string<false>(fmt, format_handler(out, fmt, args, loc));
+/**
+ * Constructs `std::system_error` with a message formatted with
+ * `fmt::format(fmt, args...)`.
+ * `error_code` is a system error code as given by `errno`.
+ *
+ * **Example**:
+ *
+ *     // This throws std::system_error with the description
+ *     //   cannot open file 'madeup': No such file or directory
+ *     // or similar (system message may vary).
+ *     const char* filename = "madeup";
+ *     FILE* file = fopen(filename, "r");
+ *     if (!file)
+ *       throw fmt::system_error(errno, "cannot open file '{}'", filename);
+ */
+template <typename... T>
+auto system_error(int error_code, format_string<T...> fmt, T&&... args)
+    -> std::system_error {
+  return vsystem_error(error_code, fmt.str, vargs<T...>{{args...}});
 }
 
-FMT_BEGIN_EXPORT
-
-#ifndef FMT_HEADER_ONLY
-extern template FMT_API void vformat_to(buffer<char>&, string_view,
-                                        typename vformat_args<>::type,
-                                        locale_ref);
-extern template FMT_API auto thousands_sep_impl<char>(locale_ref)
-    -> thousands_sep_result<char>;
-extern template FMT_API auto thousands_sep_impl<wchar_t>(locale_ref)
-    -> thousands_sep_result<wchar_t>;
-extern template FMT_API auto decimal_point_impl(locale_ref) -> char;
-extern template FMT_API auto decimal_point_impl(locale_ref) -> wchar_t;
-#endif  // FMT_HEADER_ONLY
+/**
+ * Formats an error message for an error returned by an operating system or a
+ * language runtime, for example a file opening error, and writes it to `out`.
+ * The format is the same as the one used by `std::system_error(ec, message)`
+ * where `ec` is `std::error_code(error_code, std::generic_category())`.
+ * It is implementation-defined but normally looks like:
+ *
+ *     <message>: <system-message>
+ *
+ * where `<message>` is the passed message and `<system-message>` is the system
+ * message corresponding to the error code.
+ * `error_code` is a system error code as given by `errno`.
+ */
+FMT_API void format_system_error(detail::buffer<char>& out, int error_code,
+                                 const char* message) noexcept;
 
-FMT_END_EXPORT
+// Reports a system error without throwing an exception.
+// Can be used to report errors from destructors.
+FMT_API void report_system_error(int error_code, const char* message) noexcept;
 
-template <typename T, typename Char, type TYPE>
-template <typename FormatContext>
-FMT_CONSTEXPR FMT_INLINE auto native_formatter<T, Char, TYPE>::format(
-    const T& val, FormatContext& ctx) const -> decltype(ctx.out()) {
-  if (specs_.width_ref.kind == arg_id_kind::none &&
-      specs_.precision_ref.kind == arg_id_kind::none) {
-    return write<Char>(ctx.out(), val, specs_, ctx.locale());
-  }
-  auto specs = specs_;
-  handle_dynamic_spec<width_checker>(specs.width, specs.width_ref, ctx);
-  handle_dynamic_spec<precision_checker>(specs.precision, specs.precision_ref,
-                                         ctx);
-  return write<Char>(ctx.out(), val, specs, ctx.locale());
+inline auto vformat(locale_ref loc, string_view fmt, format_args args)
+    -> std::string {
+  auto buf = memory_buffer();
+  detail::vformat_to(buf, fmt, args, loc);
+  return {buf.data(), buf.size()};
 }
 
-}  // namespace detail
-
-FMT_BEGIN_EXPORT
+template <typename... T>
+FMT_INLINE auto format(locale_ref loc, format_string<T...> fmt, T&&... args)
+    -> std::string {
+  return vformat(loc, fmt.str, vargs<T...>{{args...}});
+}
 
-template <typename Char>
-struct formatter<detail::float128, Char>
-    : detail::native_formatter<detail::float128, Char,
-                               detail::type::float_type> {};
+template <typename OutputIt,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
+auto vformat_to(OutputIt out, locale_ref loc, string_view fmt, format_args args)
+    -> OutputIt {
+  auto&& buf = detail::get_buffer<char>(out);
+  detail::vformat_to(buf, fmt, args, loc);
+  return detail::get_iterator(buf, out);
+}
 
-#if FMT_USE_USER_DEFINED_LITERALS
-inline namespace literals {
-/**
- * User-defined literal equivalent of `fmt::arg`.
- *
- * **Example**:
- *
- *     using namespace fmt::literals;
- *     fmt::print("The answer is {answer}.", "answer"_a=42);
- */
-#  if FMT_USE_NONTYPE_TEMPLATE_ARGS
-template <detail_exported::fixed_string Str> constexpr auto operator""_a() {
-  using char_t = remove_cvref_t<decltype(Str.data[0])>;
-  return detail::udl_arg<char_t, sizeof(Str.data) / sizeof(char_t), Str>();
+template <typename OutputIt, typename... T,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
+FMT_INLINE auto format_to(OutputIt out, locale_ref loc, format_string<T...> fmt,
+                          T&&... args) -> OutputIt {
+  return fmt::vformat_to(out, loc, fmt.str, vargs<T...>{{args...}});
 }
-#  else
-constexpr auto operator""_a(const char* s, size_t) -> detail::udl_arg<char> {
-  return {s};
+
+template <typename... T>
+FMT_NODISCARD FMT_INLINE auto formatted_size(locale_ref loc,
+                                             format_string<T...> fmt,
+                                             T&&... args) -> size_t {
+  auto buf = detail::counting_buffer<>();
+  detail::vformat_to(buf, fmt.str, vargs<T...>{{args...}}, loc);
+  return buf.count();
 }
-#  endif
-}  // namespace literals
-#endif  // FMT_USE_USER_DEFINED_LITERALS
 
 FMT_API auto vformat(string_view fmt, format_args args) -> std::string;
 
@@ -4354,61 +4346,45 @@ FMT_API auto vformat(string_view fmt, format_args args) -> std::string;
 template <typename... T>
 FMT_NODISCARD FMT_INLINE auto format(format_string<T...> fmt, T&&... args)
     -> std::string {
-  return vformat(fmt, fmt::make_format_args(args...));
+  return vformat(fmt.str, vargs<T...>{{args...}});
 }
 
-template <typename Locale, FMT_ENABLE_IF(detail::is_locale<Locale>::value)>
-inline auto vformat(const Locale& loc, string_view fmt, format_args args)
-    -> std::string {
-  return detail::vformat(loc, fmt, args);
+/**
+ * Converts `value` to `std::string` using the default format for type `T`.
+ *
+ * **Example**:
+ *
+ *     std::string answer = fmt::to_string(42);
+ */
+template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+FMT_NODISCARD FMT_CONSTEXPR_STRING auto to_string(T value) -> std::string {
+  // The buffer should be large enough to store the number including the sign
+  // or "false" for bool.
+  char buffer[max_of(detail::digits10<T>() + 2, 5)];
+  return {buffer, detail::write<char>(buffer, value)};
 }
 
-template <typename Locale, typename... T,
-          FMT_ENABLE_IF(detail::is_locale<Locale>::value)>
-inline auto format(const Locale& loc, format_string<T...> fmt, T&&... args)
+template <typename T, FMT_ENABLE_IF(detail::use_format_as<T>::value)>
+FMT_NODISCARD FMT_CONSTEXPR_STRING auto to_string(const T& value)
     -> std::string {
-  return fmt::vformat(loc, string_view(fmt), fmt::make_format_args(args...));
-}
-
-template <typename OutputIt, typename Locale,
-          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value&&
-                            detail::is_locale<Locale>::value)>
-auto vformat_to(OutputIt out, const Locale& loc, string_view fmt,
-                format_args args) -> OutputIt {
-  using detail::get_buffer;
-  auto&& buf = get_buffer<char>(out);
-  detail::vformat_to(buf, fmt, args, detail::locale_ref(loc));
-  return detail::get_iterator(buf, out);
-}
-
-template <typename OutputIt, typename Locale, typename... T,
-          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value&&
-                            detail::is_locale<Locale>::value)>
-FMT_INLINE auto format_to(OutputIt out, const Locale& loc,
-                          format_string<T...> fmt, T&&... args) -> OutputIt {
-  return vformat_to(out, loc, fmt, fmt::make_format_args(args...));
+  return to_string(format_as(value));
 }
 
-template <typename Locale, typename... T,
-          FMT_ENABLE_IF(detail::is_locale<Locale>::value)>
-FMT_NODISCARD FMT_INLINE auto formatted_size(const Locale& loc,
-                                             format_string<T...> fmt,
-                                             T&&... args) -> size_t {
-  auto buf = detail::counting_buffer<>();
-  detail::vformat_to<char>(buf, fmt, fmt::make_format_args(args...),
-                           detail::locale_ref(loc));
-  return buf.count();
+template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value &&
+                                    !detail::use_format_as<T>::value)>
+FMT_NODISCARD FMT_CONSTEXPR_STRING auto to_string(const T& value)
+    -> std::string {
+  auto buffer = memory_buffer();
+  detail::write<char>(appender(buffer), value);
+  return {buffer.data(), buffer.size()};
 }
 
 FMT_END_EXPORT
-
 FMT_END_NAMESPACE
 
 #ifdef FMT_HEADER_ONLY
 #  define FMT_FUNC inline
 #  include "format-inl.h"
-#else
-#  define FMT_FUNC
 #endif
 
 // Restore _LIBCPP_REMOVE_TRANSITIVE_INCLUDES.
diff --git a/contrib/fmt/include/fmt/locale.h b/contrib/fmt/include/fmt/locale.h
deleted file mode 100644
index 7571b5261b..0000000000
--- a/contrib/fmt/include/fmt/locale.h
+++ /dev/null
@@ -1,2 +0,0 @@
-#include "xchar.h"
-#warning fmt/locale.h is deprecated, include fmt/format.h or fmt/xchar.h instead
diff --git a/contrib/fmt/include/fmt/os.h b/contrib/fmt/include/fmt/os.h
index 5c85ea08ff..94d730de28 100644
--- a/contrib/fmt/include/fmt/os.h
+++ b/contrib/fmt/include/fmt/os.h
@@ -29,7 +29,8 @@
 #  if (FMT_HAS_INCLUDE(<fcntl.h>) || defined(__APPLE__) || \
        defined(__linux__)) &&                              \
       (!defined(WINAPI_FAMILY) ||                          \
-       (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
+       (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP)) &&    \
+      !defined(__wasm__)
 #    include <fcntl.h>  // for O_RDONLY
 #    define FMT_USE_FCNTL 1
 #  else
@@ -118,7 +119,7 @@ FMT_API void format_windows_error(buffer<char>& out, int error_code,
                                   const char* message) noexcept;
 }
 
-FMT_API std::system_error vwindows_error(int error_code, string_view format_str,
+FMT_API std::system_error vwindows_error(int error_code, string_view fmt,
                                          format_args args);
 
 /**
@@ -135,10 +136,9 @@ FMT_API std::system_error vwindows_error(int error_code, string_view format_str,
  * **Example**:
  *
  *     // This throws a system_error with the description
- *     //   cannot open file 'madeup': The system cannot find the file
- * specified.
- *     // or similar (system message may vary).
- *     const char *filename = "madeup";
+ *     //   cannot open file 'foo': The system cannot find the file specified.
+ *     // or similar (system message may vary) if the file doesn't exist.
+ *     const char *filename = "foo";
  *     LPOFSTRUCT of = LPOFSTRUCT();
  *     HFILE file = OpenFile(filename, &of, OF_READ);
  *     if (file == HFILE_ERROR) {
@@ -146,10 +146,10 @@ FMT_API std::system_error vwindows_error(int error_code, string_view format_str,
  *                                "cannot open file '{}'", filename);
  *     }
  */
-template <typename... Args>
-std::system_error windows_error(int error_code, string_view message,
-                                const Args&... args) {
-  return vwindows_error(error_code, message, fmt::make_format_args(args...));
+template <typename... T>
+auto windows_error(int error_code, string_view message, const T&... args)
+    -> std::system_error {
+  return vwindows_error(error_code, message, vargs<T...>{{args...}});
 }
 
 // Reports a Windows error without throwing an exception.
@@ -164,8 +164,8 @@ inline auto system_category() noexcept -> const std::error_category& {
 // std::system is not available on some platforms such as iOS (#2248).
 #ifdef __OSX__
 template <typename S, typename... Args, typename Char = char_t<S>>
-void say(const S& format_str, Args&&... args) {
-  std::system(format("say \"{}\"", format(format_str, args...)).c_str());
+void say(const S& fmt, Args&&... args) {
+  std::system(format("say \"{}\"", format(fmt, args...)).c_str());
 }
 #endif
 
@@ -176,24 +176,24 @@ class buffered_file {
 
   friend class file;
 
-  explicit buffered_file(FILE* f) : file_(f) {}
+  inline explicit buffered_file(FILE* f) : file_(f) {}
 
  public:
   buffered_file(const buffered_file&) = delete;
   void operator=(const buffered_file&) = delete;
 
   // Constructs a buffered_file object which doesn't represent any file.
-  buffered_file() noexcept : file_(nullptr) {}
+  inline buffered_file() noexcept : file_(nullptr) {}
 
   // Destroys the object closing the file it represents if any.
   FMT_API ~buffered_file() noexcept;
 
  public:
-  buffered_file(buffered_file&& other) noexcept : file_(other.file_) {
+  inline buffered_file(buffered_file&& other) noexcept : file_(other.file_) {
     other.file_ = nullptr;
   }
 
-  auto operator=(buffered_file&& other) -> buffered_file& {
+  inline auto operator=(buffered_file&& other) -> buffered_file& {
     close();
     file_ = other.file_;
     other.file_ = nullptr;
@@ -207,13 +207,13 @@ class buffered_file {
   FMT_API void close();
 
   // Returns the pointer to a FILE object representing this file.
-  auto get() const noexcept -> FILE* { return file_; }
+  inline auto get() const noexcept -> FILE* { return file_; }
 
   FMT_API auto descriptor() const -> int;
 
   template <typename... T>
   inline void print(string_view fmt, const T&... args) {
-    const auto& vargs = fmt::make_format_args(args...);
+    fmt::vargs<T...> vargs = {{args...}};
     detail::is_locking<T...>() ? fmt::vprint_buffered(file_, fmt, vargs)
                                : fmt::vprint(file_, fmt, vargs);
   }
@@ -248,7 +248,7 @@ class FMT_API file {
   };
 
   // Constructs a file object which doesn't represent any file.
-  file() noexcept : fd_(-1) {}
+  inline file() noexcept : fd_(-1) {}
 
   // Opens a file and constructs a file object representing this file.
   file(cstring_view path, int oflag);
@@ -257,10 +257,10 @@ class FMT_API file {
   file(const file&) = delete;
   void operator=(const file&) = delete;
 
-  file(file&& other) noexcept : fd_(other.fd_) { other.fd_ = -1; }
+  inline file(file&& other) noexcept : fd_(other.fd_) { other.fd_ = -1; }
 
   // Move assignment is not noexcept because close may throw.
-  auto operator=(file&& other) -> file& {
+  inline auto operator=(file&& other) -> file& {
     close();
     fd_ = other.fd_;
     other.fd_ = -1;
@@ -271,7 +271,7 @@ class FMT_API file {
   ~file() noexcept;
 
   // Returns the file descriptor.
-  auto descriptor() const noexcept -> int { return fd_; }
+  inline auto descriptor() const noexcept -> int { return fd_; }
 
   // Closes the file.
   void close();
@@ -324,9 +324,9 @@ auto getpagesize() -> long;
 namespace detail {
 
 struct buffer_size {
-  buffer_size() = default;
+  constexpr buffer_size() = default;
   size_t value = 0;
-  auto operator=(size_t val) const -> buffer_size {
+  FMT_CONSTEXPR auto operator=(size_t val) const -> buffer_size {
     auto bs = buffer_size();
     bs.value = val;
     return bs;
@@ -337,7 +337,7 @@ struct ostream_params {
   int oflag = file::WRONLY | file::CREATE | file::TRUNC;
   size_t buffer_size = BUFSIZ > 32768 ? BUFSIZ : 32768;
 
-  ostream_params() {}
+  constexpr ostream_params() {}
 
   template <typename... T>
   ostream_params(T... params, int new_oflag) : ostream_params(params...) {
@@ -358,59 +358,47 @@ struct ostream_params {
 #  endif
 };
 
-class file_buffer final : public buffer<char> {
+}  // namespace detail
+
+FMT_INLINE_VARIABLE constexpr auto buffer_size = detail::buffer_size();
+
+/// A fast buffered output stream for writing from a single thread. Writing from
+/// multiple threads without external synchronization may result in a data race.
+class ostream : private detail::buffer<char> {
  private:
   file file_;
 
+  FMT_API ostream(cstring_view path, const detail::ostream_params& params);
+
   FMT_API static void grow(buffer<char>& buf, size_t);
 
  public:
-  FMT_API file_buffer(cstring_view path, const ostream_params& params);
-  FMT_API file_buffer(file_buffer&& other) noexcept;
-  FMT_API ~file_buffer();
+  FMT_API ostream(ostream&& other) noexcept;
+  FMT_API ~ostream();
+
+  operator writer() {
+    detail::buffer<char>& buf = *this;
+    return buf;
+  }
 
-  void flush() {
+  inline void flush() {
     if (size() == 0) return;
     file_.write(data(), size() * sizeof(data()[0]));
     clear();
   }
 
-  void close() {
-    flush();
-    file_.close();
-  }
-};
-
-}  // namespace detail
-
-constexpr auto buffer_size = detail::buffer_size();
-
-/// A fast output stream for writing from a single thread. Writing from
-/// multiple threads without external synchronization may result in a data race.
-class FMT_API ostream {
- private:
-  FMT_MSC_WARNING(suppress : 4251)
-  detail::file_buffer buffer_;
-
-  ostream(cstring_view path, const detail::ostream_params& params)
-      : buffer_(path, params) {}
-
- public:
-  ostream(ostream&& other) : buffer_(std::move(other.buffer_)) {}
-
-  ~ostream();
-
-  void flush() { buffer_.flush(); }
-
   template <typename... T>
   friend auto output_file(cstring_view path, T... params) -> ostream;
 
-  void close() { buffer_.close(); }
+  inline void close() {
+    flush();
+    file_.close();
+  }
 
   /// Formats `args` according to specifications in `fmt` and writes the
   /// output to the file.
   template <typename... T> void print(format_string<T...> fmt, T&&... args) {
-    vformat_to(appender(buffer_), fmt, fmt::make_format_args(args...));
+    vformat_to(appender(*this), fmt.str, vargs<T...>{{args...}});
   }
 };
 
diff --git a/contrib/fmt/include/fmt/ostream.h b/contrib/fmt/include/fmt/ostream.h
index 98faef659f..bf2371b799 100644
--- a/contrib/fmt/include/fmt/ostream.h
+++ b/contrib/fmt/include/fmt/ostream.h
@@ -22,11 +22,19 @@
 
 #include "chrono.h"  // formatbuf
 
+#ifdef _MSVC_STL_UPDATE
+#  define FMT_MSVC_STL_UPDATE _MSVC_STL_UPDATE
+#elif defined(_MSC_VER) && _MSC_VER < 1912  // VS 15.5
+#  define FMT_MSVC_STL_UPDATE _MSVC_LANG
+#else
+#  define FMT_MSVC_STL_UPDATE 0
+#endif
+
 FMT_BEGIN_NAMESPACE
 namespace detail {
 
-// Generate a unique explicit instantion in every translation unit using a tag
-// type in an anonymous namespace.
+// Generate a unique explicit instantiation in every translation unit using a
+// tag type in an anonymous namespace.
 namespace {
 struct file_access_tag {};
 }  // namespace
@@ -35,53 +43,18 @@ class file_access {
   friend auto get_file(BufType& obj) -> FILE* { return obj.*FileMemberPtr; }
 };
 
-#if FMT_MSC_VERSION
+#if FMT_MSVC_STL_UPDATE
 template class file_access<file_access_tag, std::filebuf,
                            &std::filebuf::_Myfile>;
 auto get_file(std::filebuf&) -> FILE*;
 #endif
 
-inline auto write_ostream_unicode(std::ostream& os, fmt::string_view data)
-    -> bool {
-  FILE* f = nullptr;
-#if FMT_MSC_VERSION && FMT_USE_RTTI
-  if (auto* buf = dynamic_cast<std::filebuf*>(os.rdbuf()))
-    f = get_file(*buf);
-  else
-    return false;
-#elif defined(_WIN32) && defined(__GLIBCXX__) && FMT_USE_RTTI
-  auto* rdbuf = os.rdbuf();
-  if (auto* sfbuf = dynamic_cast<__gnu_cxx::stdio_sync_filebuf<char>*>(rdbuf))
-    f = sfbuf->file();
-  else if (auto* fbuf = dynamic_cast<__gnu_cxx::stdio_filebuf<char>*>(rdbuf))
-    f = fbuf->file();
-  else
-    return false;
-#else
-  ignore_unused(os, data, f);
-#endif
-#ifdef _WIN32
-  if (f) {
-    int fd = _fileno(f);
-    if (_isatty(fd)) {
-      os.flush();
-      return write_console(fd, data);
-    }
-  }
-#endif
-  return false;
-}
-inline auto write_ostream_unicode(std::wostream&,
-                                  fmt::basic_string_view<wchar_t>) -> bool {
-  return false;
-}
-
 // Write the content of buf to os.
 // It is a separate function rather than a part of vprint to simplify testing.
 template <typename Char>
 void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
   const Char* buf_data = buf.data();
-  using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;
+  using unsigned_streamsize = make_unsigned_t<std::streamsize>;
   unsigned_streamsize size = buf.size();
   unsigned_streamsize max_size = to_unsigned(max_value<std::streamsize>());
   do {
@@ -92,21 +65,9 @@ void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
   } while (size != 0);
 }
 
-template <typename Char, typename T>
-void format_value(buffer<Char>& buf, const T& value) {
-  auto&& format_buf = formatbuf<std::basic_streambuf<Char>>(buf);
-  auto&& output = std::basic_ostream<Char>(&format_buf);
-#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
-  output.imbue(std::locale::classic());  // The default is always unlocalized.
-#endif
-  output << value;
-  output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
-}
-
 template <typename T> struct streamed_view {
   const T& value;
 };
-
 }  // namespace detail
 
 // Formats an object of type T that has an overloaded ostream operator<<.
@@ -117,7 +78,11 @@ struct basic_ostream_formatter : formatter<basic_string_view<Char>, Char> {
   template <typename T, typename Context>
   auto format(const T& value, Context& ctx) const -> decltype(ctx.out()) {
     auto buffer = basic_memory_buffer<Char>();
-    detail::format_value(buffer, value);
+    auto&& formatbuf = detail::formatbuf<std::basic_streambuf<Char>>(buffer);
+    auto&& output = std::basic_ostream<Char>(&formatbuf);
+    output.imbue(std::locale::classic());  // The default is always unlocalized.
+    output << value;
+    output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
     return formatter<basic_string_view<Char>, Char>::format(
         {buffer.data(), buffer.size()}, ctx);
   }
@@ -148,24 +113,30 @@ constexpr auto streamed(const T& value) -> detail::streamed_view<T> {
   return {value};
 }
 
-namespace detail {
-
-inline void vprint_directly(std::ostream& os, string_view format_str,
-                            format_args args) {
+inline void vprint(std::ostream& os, string_view fmt, format_args args) {
   auto buffer = memory_buffer();
-  detail::vformat_to(buffer, format_str, args);
-  detail::write_buffer(os, buffer);
-}
-
-}  // namespace detail
-
-FMT_EXPORT template <typename Char>
-void vprint(std::basic_ostream<Char>& os,
-            basic_string_view<type_identity_t<Char>> format_str,
-            typename detail::vformat_args<Char>::type args) {
-  auto buffer = basic_memory_buffer<Char>();
-  detail::vformat_to(buffer, format_str, args);
-  if (detail::write_ostream_unicode(os, {buffer.data(), buffer.size()})) return;
+  detail::vformat_to(buffer, fmt, args);
+  FILE* f = nullptr;
+#if FMT_MSVC_STL_UPDATE && FMT_USE_RTTI
+  if (auto* buf = dynamic_cast<std::filebuf*>(os.rdbuf()))
+    f = detail::get_file(*buf);
+#elif defined(_WIN32) && defined(__GLIBCXX__) && FMT_USE_RTTI
+  auto* rdbuf = os.rdbuf();
+  if (auto* sfbuf = dynamic_cast<__gnu_cxx::stdio_sync_filebuf<char>*>(rdbuf))
+    f = sfbuf->file();
+  else if (auto* fbuf = dynamic_cast<__gnu_cxx::stdio_filebuf<char>*>(rdbuf))
+    f = fbuf->file();
+#endif
+#ifdef _WIN32
+  if (f) {
+    int fd = _fileno(f);
+    if (_isatty(fd)) {
+      os.flush();
+      if (detail::write_console(fd, {buffer.data(), buffer.size()})) return;
+    }
+  }
+#endif
+  detail::ignore_unused(f);
   detail::write_buffer(os, buffer);
 }
 
@@ -178,32 +149,17 @@ void vprint(std::basic_ostream<Char>& os,
  */
 FMT_EXPORT template <typename... T>
 void print(std::ostream& os, format_string<T...> fmt, T&&... args) {
-  const auto& vargs = fmt::make_format_args(args...);
-  if (detail::use_utf8())
-    vprint(os, fmt, vargs);
-  else
-    detail::vprint_directly(os, fmt, vargs);
-}
-
-FMT_EXPORT
-template <typename... Args>
-void print(std::wostream& os,
-           basic_format_string<wchar_t, type_identity_t<Args>...> fmt,
-           Args&&... args) {
-  vprint(os, fmt, fmt::make_format_args<buffered_context<wchar_t>>(args...));
+  fmt::vargs<T...> vargs = {{args...}};
+  if (detail::const_check(detail::use_utf8)) return vprint(os, fmt.str, vargs);
+  auto buffer = memory_buffer();
+  detail::vformat_to(buffer, fmt.str, vargs);
+  detail::write_buffer(os, buffer);
 }
 
 FMT_EXPORT template <typename... T>
 void println(std::ostream& os, format_string<T...> fmt, T&&... args) {
-  fmt::print(os, "{}\n", fmt::format(fmt, std::forward<T>(args)...));
-}
-
-FMT_EXPORT
-template <typename... Args>
-void println(std::wostream& os,
-             basic_format_string<wchar_t, type_identity_t<Args>...> fmt,
-             Args&&... args) {
-  print(os, L"{}\n", fmt::format(fmt, std::forward<Args>(args)...));
+  fmt::print(os, FMT_STRING("{}\n"),
+             fmt::format(fmt, std::forward<T>(args)...));
 }
 
 FMT_END_NAMESPACE
diff --git a/contrib/fmt/include/fmt/posix.h b/contrib/fmt/include/fmt/posix.h
deleted file mode 100644
index da19e9d530..0000000000
--- a/contrib/fmt/include/fmt/posix.h
+++ /dev/null
@@ -1,2 +0,0 @@
-#include "os.h"
-#warning "fmt/posix.h is deprecated; use fmt/os.h instead"
diff --git a/contrib/fmt/include/fmt/printf.h b/contrib/fmt/include/fmt/printf.h
index ee4b06fd5e..cc066d8c07 100644
--- a/contrib/fmt/include/fmt/printf.h
+++ b/contrib/fmt/include/fmt/printf.h
@@ -9,7 +9,7 @@
 #define FMT_PRINTF_H_
 
 #ifndef FMT_MODULE
-#  include <algorithm>  // std::max
+#  include <algorithm>  // std::find
 #  include <limits>     // std::numeric_limits
 #endif
 
@@ -18,10 +18,6 @@
 FMT_BEGIN_NAMESPACE
 FMT_BEGIN_EXPORT
 
-template <typename T> struct printf_formatter {
-  printf_formatter() = delete;
-};
-
 template <typename Char> class basic_printf_context {
  private:
   basic_appender<Char> out_;
@@ -33,8 +29,7 @@ template <typename Char> class basic_printf_context {
 
  public:
   using char_type = Char;
-  using parse_context_type = basic_format_parse_context<Char>;
-  template <typename T> using formatter_type = printf_formatter<T>;
+  enum { builtin_types = 1 };
 
   /// Constructs a `printf_context` object. References to the arguments are
   /// stored in the context object so make sure they have appropriate lifetimes.
@@ -45,7 +40,7 @@ template <typename Char> class basic_printf_context {
   auto out() -> basic_appender<Char> { return out_; }
   void advance_to(basic_appender<Char>) {}
 
-  auto locale() -> detail::locale_ref { return {}; }
+  auto locale() -> locale_ref { return {}; }
 
   auto arg(int id) const -> basic_format_arg<basic_printf_context> {
     return args_.get(id);
@@ -54,14 +49,30 @@ template <typename Char> class basic_printf_context {
 
 namespace detail {
 
+// Return the result via the out param to workaround gcc bug 77539.
+template <bool IS_CONSTEXPR, typename T, typename Ptr = const T*>
+FMT_CONSTEXPR auto find(Ptr first, Ptr last, T value, Ptr& out) -> bool {
+  for (out = first; out != last; ++out) {
+    if (*out == value) return true;
+  }
+  return false;
+}
+
+template <>
+inline auto find<false, char>(const char* first, const char* last, char value,
+                              const char*& out) -> bool {
+  out =
+      static_cast<const char*>(memchr(first, value, to_unsigned(last - first)));
+  return out != nullptr;
+}
+
 // Checks if a value fits in int - used to avoid warnings about comparing
 // signed and unsigned integers.
-template <bool IsSigned> struct int_checker {
+template <bool IS_SIGNED> struct int_checker {
   template <typename T> static auto fits_in_int(T value) -> bool {
-    unsigned max = to_unsigned(max_value<int>());
-    return value <= max;
+    return value <= to_unsigned(max_value<int>());
   }
-  static auto fits_in_int(bool) -> bool { return true; }
+  inline static auto fits_in_int(bool) -> bool { return true; }
 };
 
 template <> struct int_checker<true> {
@@ -69,7 +80,7 @@ template <> struct int_checker<true> {
     return value >= (std::numeric_limits<int>::min)() &&
            value <= max_value<int>();
   }
-  static auto fits_in_int(int) -> bool { return true; }
+  inline static auto fits_in_int(int) -> bool { return true; }
 };
 
 struct printf_precision_handler {
@@ -77,7 +88,7 @@ struct printf_precision_handler {
   auto operator()(T value) -> int {
     if (!int_checker<std::numeric_limits<T>::is_signed>::fits_in_int(value))
       report_error("number is too big");
-    return (std::max)(static_cast<int>(value), 0);
+    return max_of(static_cast<int>(value), 0);
   }
 
   template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
@@ -127,25 +138,19 @@ template <typename T, typename Context> class arg_converter {
     using target_type = conditional_t<std::is_same<T, void>::value, U, T>;
     if (const_check(sizeof(target_type) <= sizeof(int))) {
       // Extra casts are used to silence warnings.
-      if (is_signed) {
-        auto n = static_cast<int>(static_cast<target_type>(value));
-        arg_ = detail::make_arg<Context>(n);
-      } else {
-        using unsigned_type = typename make_unsigned_or_bool<target_type>::type;
-        auto n = static_cast<unsigned>(static_cast<unsigned_type>(value));
-        arg_ = detail::make_arg<Context>(n);
-      }
+      using unsigned_type = typename make_unsigned_or_bool<target_type>::type;
+      if (is_signed)
+        arg_ = static_cast<int>(static_cast<target_type>(value));
+      else
+        arg_ = static_cast<unsigned>(static_cast<unsigned_type>(value));
     } else {
-      if (is_signed) {
-        // glibc's printf doesn't sign extend arguments of smaller types:
-        //   std::printf("%lld", -42);  // prints "4294967254"
-        // but we don't have to do the same because it's a UB.
-        auto n = static_cast<long long>(value);
-        arg_ = detail::make_arg<Context>(n);
-      } else {
-        auto n = static_cast<typename make_unsigned_or_bool<U>::type>(value);
-        arg_ = detail::make_arg<Context>(n);
-      }
+      // glibc's printf doesn't sign extend arguments of smaller types:
+      //   std::printf("%lld", -42);  // prints "4294967254"
+      // but we don't have to do the same because it's a UB.
+      if (is_signed)
+        arg_ = static_cast<long long>(value);
+      else
+        arg_ = static_cast<typename make_unsigned_or_bool<U>::type>(value);
     }
   }
 
@@ -172,8 +177,7 @@ template <typename Context> class char_converter {
 
   template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
   void operator()(T value) {
-    auto c = static_cast<typename Context::char_type>(value);
-    arg_ = detail::make_arg<Context>(c);
+    arg_ = static_cast<typename Context::char_type>(value);
   }
 
   template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
@@ -194,13 +198,13 @@ class printf_width_handler {
   format_specs& specs_;
 
  public:
-  explicit printf_width_handler(format_specs& specs) : specs_(specs) {}
+  inline explicit printf_width_handler(format_specs& specs) : specs_(specs) {}
 
   template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
   auto operator()(T value) -> unsigned {
     auto width = static_cast<uint32_or_64_or_128_t<T>>(value);
     if (detail::is_negative(value)) {
-      specs_.align = align::left;
+      specs_.set_align(align::left);
       width = 0 - width;
     }
     unsigned int_max = to_unsigned(max_value<int>());
@@ -234,69 +238,74 @@ class printf_arg_formatter : public arg_formatter<Char> {
 
   void write_null_pointer(bool is_string = false) {
     auto s = this->specs;
-    s.type = presentation_type::none;
+    s.set_type(presentation_type::none);
     write_bytes<Char>(this->out, is_string ? "(null)" : "(nil)", s);
   }
 
+  template <typename T> void write(T value) {
+    detail::write<Char>(this->out, value, this->specs, this->locale);
+  }
+
  public:
   printf_arg_formatter(basic_appender<Char> iter, format_specs& s,
                        context_type& ctx)
       : base(make_arg_formatter(iter, s)), context_(ctx) {}
 
-  void operator()(monostate value) { base::operator()(value); }
+  void operator()(monostate value) { write(value); }
 
   template <typename T, FMT_ENABLE_IF(detail::is_integral<T>::value)>
   void operator()(T value) {
     // MSVC2013 fails to compile separate overloads for bool and Char so use
     // std::is_same instead.
     if (!std::is_same<T, Char>::value) {
-      base::operator()(value);
+      write(value);
       return;
     }
     format_specs s = this->specs;
-    if (s.type != presentation_type::none && s.type != presentation_type::chr) {
+    if (s.type() != presentation_type::none &&
+        s.type() != presentation_type::chr) {
       return (*this)(static_cast<int>(value));
     }
-    s.sign = sign::none;
-    s.alt = false;
-    s.fill = ' ';  // Ignore '0' flag for char types.
+    s.set_sign(sign::none);
+    s.clear_alt();
+    s.set_fill(' ');  // Ignore '0' flag for char types.
     // align::numeric needs to be overwritten here since the '0' flag is
     // ignored for non-numeric types
-    if (s.align == align::none || s.align == align::numeric)
-      s.align = align::right;
-    write<Char>(this->out, static_cast<Char>(value), s);
+    if (s.align() == align::none || s.align() == align::numeric)
+      s.set_align(align::right);
+    detail::write<Char>(this->out, static_cast<Char>(value), s);
   }
 
   template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
   void operator()(T value) {
-    base::operator()(value);
+    write(value);
   }
 
   void operator()(const char* value) {
     if (value)
-      base::operator()(value);
+      write(value);
     else
-      write_null_pointer(this->specs.type != presentation_type::pointer);
+      write_null_pointer(this->specs.type() != presentation_type::pointer);
   }
 
   void operator()(const wchar_t* value) {
     if (value)
-      base::operator()(value);
+      write(value);
     else
-      write_null_pointer(this->specs.type != presentation_type::pointer);
+      write_null_pointer(this->specs.type() != presentation_type::pointer);
   }
 
-  void operator()(basic_string_view<Char> value) { base::operator()(value); }
+  void operator()(basic_string_view<Char> value) { write(value); }
 
   void operator()(const void* value) {
     if (value)
-      base::operator()(value);
+      write(value);
     else
       write_null_pointer();
   }
 
   void operator()(typename basic_format_arg<context_type>::handle handle) {
-    auto parse_ctx = basic_format_parse_context<Char>({});
+    auto parse_ctx = parse_context<Char>({});
     handle.format(parse_ctx, context_);
   }
 };
@@ -305,23 +314,14 @@ template <typename Char>
 void parse_flags(format_specs& specs, const Char*& it, const Char* end) {
   for (; it != end; ++it) {
     switch (*it) {
-    case '-':
-      specs.align = align::left;
-      break;
-    case '+':
-      specs.sign = sign::plus;
-      break;
-    case '0':
-      specs.fill = '0';
-      break;
+    case '-': specs.set_align(align::left); break;
+    case '+': specs.set_sign(sign::plus); break;
+    case '0': specs.set_fill('0'); break;
     case ' ':
-      if (specs.sign != sign::plus) specs.sign = sign::space;
+      if (specs.sign() != sign::plus) specs.set_sign(sign::space);
       break;
-    case '#':
-      specs.alt = true;
-      break;
-    default:
-      return;
+    case '#': specs.set_alt(); break;
+    default:  return;
     }
   }
 }
@@ -339,7 +339,7 @@ auto parse_header(const Char*& it, const Char* end, format_specs& specs,
       ++it;
       arg_index = value != -1 ? value : max_value<int>();
     } else {
-      if (c == '0') specs.fill = '0';
+      if (c == '0') specs.set_fill('0');
       if (value != 0) {
         // Nonzero value means that we parsed width and don't need to
         // parse it or flags again, so return now.
@@ -369,43 +369,22 @@ inline auto parse_printf_presentation_type(char c, type t, bool& upper)
   using pt = presentation_type;
   constexpr auto integral_set = sint_set | uint_set | bool_set | char_set;
   switch (c) {
-  case 'd':
-    return in(t, integral_set) ? pt::dec : pt::none;
-  case 'o':
-    return in(t, integral_set) ? pt::oct : pt::none;
-  case 'X':
-    upper = true;
-    FMT_FALLTHROUGH;
-  case 'x':
-    return in(t, integral_set) ? pt::hex : pt::none;
-  case 'E':
-    upper = true;
-    FMT_FALLTHROUGH;
-  case 'e':
-    return in(t, float_set) ? pt::exp : pt::none;
-  case 'F':
-    upper = true;
-    FMT_FALLTHROUGH;
-  case 'f':
-    return in(t, float_set) ? pt::fixed : pt::none;
-  case 'G':
-    upper = true;
-    FMT_FALLTHROUGH;
-  case 'g':
-    return in(t, float_set) ? pt::general : pt::none;
-  case 'A':
-    upper = true;
-    FMT_FALLTHROUGH;
-  case 'a':
-    return in(t, float_set) ? pt::hexfloat : pt::none;
-  case 'c':
-    return in(t, integral_set) ? pt::chr : pt::none;
-  case 's':
-    return in(t, string_set | cstring_set) ? pt::string : pt::none;
-  case 'p':
-    return in(t, pointer_set | cstring_set) ? pt::pointer : pt::none;
-  default:
-    return pt::none;
+  case 'd': return in(t, integral_set) ? pt::dec : pt::none;
+  case 'o': return in(t, integral_set) ? pt::oct : pt::none;
+  case 'X': upper = true; FMT_FALLTHROUGH;
+  case 'x': return in(t, integral_set) ? pt::hex : pt::none;
+  case 'E': upper = true; FMT_FALLTHROUGH;
+  case 'e': return in(t, float_set) ? pt::exp : pt::none;
+  case 'F': upper = true; FMT_FALLTHROUGH;
+  case 'f': return in(t, float_set) ? pt::fixed : pt::none;
+  case 'G': upper = true; FMT_FALLTHROUGH;
+  case 'g': return in(t, float_set) ? pt::general : pt::none;
+  case 'A': upper = true; FMT_FALLTHROUGH;
+  case 'a': return in(t, float_set) ? pt::hexfloat : pt::none;
+  case 'c': return in(t, integral_set) ? pt::chr : pt::none;
+  case 's': return in(t, string_set | cstring_set) ? pt::string : pt::none;
+  case 'p': return in(t, pointer_set | cstring_set) ? pt::pointer : pt::none;
+  default:  return pt::none;
   }
 }
 
@@ -415,7 +394,7 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
   using iterator = basic_appender<Char>;
   auto out = iterator(buf);
   auto context = basic_printf_context<Char>(out, args);
-  auto parse_ctx = basic_format_parse_context<Char>(format);
+  auto parse_ctx = parse_context<Char>(format);
 
   // Returns the argument with specified index or, if arg_index is -1, the next
   // argument.
@@ -424,7 +403,9 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
       arg_index = parse_ctx.next_arg_id();
     else
       parse_ctx.check_arg_id(--arg_index);
-    return detail::get_arg(context, arg_index);
+    auto arg = context.arg(arg_index);
+    if (!arg) report_error("argument not found");
+    return arg;
   };
 
   const Char* start = parse_ctx.begin();
@@ -444,7 +425,7 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
     write(out, basic_string_view<Char>(start, to_unsigned(it - 1 - start)));
 
     auto specs = format_specs();
-    specs.align = align::right;
+    specs.set_align(align::right);
 
     // Parse argument index, flags and width.
     int arg_index = parse_header(it, end, specs, get_arg);
@@ -468,9 +449,9 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
     auto arg = get_arg(arg_index);
     // For d, i, o, u, x, and X conversion specifiers, if a precision is
     // specified, the '0' flag is ignored
-    if (specs.precision >= 0 && arg.is_integral()) {
+    if (specs.precision >= 0 && is_integral_type(arg.type())) {
       // Ignore '0' for non-numeric types or if '-' present.
-      specs.fill = ' ';
+      specs.set_fill(' ');
     }
     if (specs.precision >= 0 && arg.type() == type::cstring_type) {
       auto str = arg.visit(get_cstring<Char>());
@@ -478,15 +459,16 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
       auto nul = std::find(str, str_end, Char());
       auto sv = basic_string_view<Char>(
           str, to_unsigned(nul != str_end ? nul - str : specs.precision));
-      arg = make_arg<basic_printf_context<Char>>(sv);
+      arg = sv;
     }
-    if (specs.alt && arg.visit(is_zero_int())) specs.alt = false;
-    if (specs.fill.template get<Char>() == '0') {
-      if (arg.is_arithmetic() && specs.align != align::left)
-        specs.align = align::numeric;
-      else
-        specs.fill = ' ';  // Ignore '0' flag for non-numeric types or if '-'
-                           // flag is also present.
+    if (specs.alt() && arg.visit(is_zero_int())) specs.clear_alt();
+    if (specs.fill_unit<Char>() == '0') {
+      if (is_arithmetic_type(arg.type()) && specs.align() != align::left) {
+        specs.set_align(align::numeric);
+      } else {
+        // Ignore '0' flag for non-numeric types or if '-' flag is also present.
+        specs.set_fill(' ');
+      }
     }
 
     // Parse length and convert the argument to the required type.
@@ -511,44 +493,34 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
         convert_arg<long>(arg, t);
       }
       break;
-    case 'j':
-      convert_arg<intmax_t>(arg, t);
-      break;
-    case 'z':
-      convert_arg<size_t>(arg, t);
-      break;
-    case 't':
-      convert_arg<std::ptrdiff_t>(arg, t);
-      break;
+    case 'j': convert_arg<intmax_t>(arg, t); break;
+    case 'z': convert_arg<size_t>(arg, t); break;
+    case 't': convert_arg<std::ptrdiff_t>(arg, t); break;
     case 'L':
       // printf produces garbage when 'L' is omitted for long double, no
       // need to do the same.
       break;
-    default:
-      --it;
-      convert_arg<void>(arg, c);
+    default: --it; convert_arg<void>(arg, c);
     }
 
     // Parse type.
     if (it == end) report_error("invalid format string");
     char type = static_cast<char>(*it++);
-    if (arg.is_integral()) {
+    if (is_integral_type(arg.type())) {
       // Normalize type.
       switch (type) {
       case 'i':
-      case 'u':
-        type = 'd';
-        break;
+      case 'u': type = 'd'; break;
       case 'c':
         arg.visit(char_converter<basic_printf_context<Char>>(arg));
         break;
       }
     }
     bool upper = false;
-    specs.type = parse_printf_presentation_type(type, arg.type(), upper);
-    if (specs.type == presentation_type::none)
+    specs.set_type(parse_printf_presentation_type(type, arg.type(), upper));
+    if (specs.type() == presentation_type::none)
       report_error("invalid format specifier");
-    specs.upper = upper;
+    if (upper) specs.set_upper();
 
     start = it;
 
@@ -569,8 +541,8 @@ using wprintf_args = basic_format_args<wprintf_context>;
 /// arguments and can be implicitly converted to `printf_args`.
 template <typename Char = char, typename... T>
 inline auto make_printf_args(T&... args)
-    -> decltype(make_format_args<basic_printf_context<Char>>(args...)) {
-  return make_format_args<basic_printf_context<Char>>(args...);
+    -> decltype(fmt::make_format_args<basic_printf_context<Char>>(args...)) {
+  return fmt::make_format_args<basic_printf_context<Char>>(args...);
 }
 
 template <typename Char> struct vprintf_args {
@@ -583,7 +555,7 @@ inline auto vsprintf(basic_string_view<Char> fmt,
     -> std::basic_string<Char> {
   auto buf = basic_memory_buffer<Char>();
   detail::vprintf(buf, fmt, args);
-  return to_string(buf);
+  return {buf.data(), buf.size()};
 }
 
 /**
@@ -594,15 +566,19 @@ inline auto vsprintf(basic_string_view<Char> fmt,
  *
  *     std::string message = fmt::sprintf("The answer is %d", 42);
  */
-template <typename S, typename... T, typename Char = char_t<S>>
-inline auto sprintf(const S& fmt, const T&... args) -> std::basic_string<Char> {
-  return vsprintf(detail::to_string_view(fmt),
-                  fmt::make_format_args<basic_printf_context<Char>>(args...));
+template <typename... T>
+inline auto sprintf(string_view fmt, const T&... args) -> std::string {
+  return vsprintf(fmt, make_printf_args(args...));
+}
+template <typename... T>
+FMT_DEPRECATED auto sprintf(basic_string_view<wchar_t> fmt, const T&... args)
+    -> std::wstring {
+  return vsprintf(fmt, make_printf_args<wchar_t>(args...));
 }
 
 template <typename Char>
-inline auto vfprintf(std::FILE* f, basic_string_view<Char> fmt,
-                     typename vprintf_args<Char>::type args) -> int {
+auto vfprintf(std::FILE* f, basic_string_view<Char> fmt,
+              typename vprintf_args<Char>::type args) -> int {
   auto buf = basic_memory_buffer<Char>();
   detail::vprintf(buf, fmt, args);
   size_t size = buf.size();
@@ -619,17 +595,14 @@ inline auto vfprintf(std::FILE* f, basic_string_view<Char> fmt,
  *
  *     fmt::fprintf(stderr, "Don't %s!", "panic");
  */
-template <typename S, typename... T, typename Char = char_t<S>>
-inline auto fprintf(std::FILE* f, const S& fmt, const T&... args) -> int {
-  return vfprintf(f, detail::to_string_view(fmt),
-                  make_printf_args<Char>(args...));
+template <typename... T>
+inline auto fprintf(std::FILE* f, string_view fmt, const T&... args) -> int {
+  return vfprintf(f, fmt, make_printf_args(args...));
 }
-
-template <typename Char>
-FMT_DEPRECATED inline auto vprintf(basic_string_view<Char> fmt,
-                                   typename vprintf_args<Char>::type args)
-    -> int {
-  return vfprintf(stdout, fmt, args);
+template <typename... T>
+FMT_DEPRECATED auto fprintf(std::FILE* f, basic_string_view<wchar_t> fmt,
+                            const T&... args) -> int {
+  return vfprintf(f, fmt, make_printf_args<wchar_t>(args...));
 }
 
 /**
@@ -644,11 +617,6 @@ template <typename... T>
 inline auto printf(string_view fmt, const T&... args) -> int {
   return vfprintf(stdout, fmt, make_printf_args(args...));
 }
-template <typename... T>
-FMT_DEPRECATED inline auto printf(basic_string_view<wchar_t> fmt,
-                                  const T&... args) -> int {
-  return vfprintf(stdout, fmt, make_printf_args<wchar_t>(args...));
-}
 
 FMT_END_EXPORT
 FMT_END_NAMESPACE
diff --git a/contrib/fmt/include/fmt/ranges.h b/contrib/fmt/include/fmt/ranges.h
index f387903cf6..36b38e2963 100644
--- a/contrib/fmt/include/fmt/ranges.h
+++ b/contrib/fmt/include/fmt/ranges.h
@@ -11,7 +11,6 @@
 #ifndef FMT_MODULE
 #  include <initializer_list>
 #  include <iterator>
-#  include <string>
 #  include <tuple>
 #  include <type_traits>
 #  include <utility>
@@ -19,6 +18,13 @@
 
 #include "format.h"
 
+#if FMT_HAS_CPP_ATTRIBUTE(clang::lifetimebound)
+#  define FMT_LIFETIMEBOUND [[clang::lifetimebound]]
+#else
+#  define FMT_LIFETIMEBOUND
+#endif
+FMT_PRAGMA_CLANG(diagnostic error "-Wreturn-stack-address")
+
 FMT_BEGIN_NAMESPACE
 
 FMT_EXPORT
@@ -31,7 +37,7 @@ template <typename T> class is_map {
   template <typename> static void check(...);
 
  public:
-  static constexpr const bool value =
+  static constexpr bool value =
       !std::is_void<decltype(check<T>(nullptr))>::value;
 };
 
@@ -40,29 +46,16 @@ template <typename T> class is_set {
   template <typename> static void check(...);
 
  public:
-  static constexpr const bool value =
+  static constexpr bool value =
       !std::is_void<decltype(check<T>(nullptr))>::value && !is_map<T>::value;
 };
 
-template <typename... Ts> struct conditional_helper {};
-
-template <typename T, typename _ = void> struct is_range_ : std::false_type {};
-
-#if !FMT_MSC_VERSION || FMT_MSC_VERSION > 1800
-
-#  define FMT_DECLTYPE_RETURN(val)  \
-    ->decltype(val) { return val; } \
-    static_assert(                  \
-        true, "")  // This makes it so that a semicolon is required after the
-                   // macro, which helps clang-format handle the formatting.
-
 // C array overload
-template <typename T, std::size_t N>
+template <typename T, size_t N>
 auto range_begin(const T (&arr)[N]) -> const T* {
   return arr;
 }
-template <typename T, std::size_t N>
-auto range_end(const T (&arr)[N]) -> const T* {
+template <typename T, size_t N> auto range_end(const T (&arr)[N]) -> const T* {
   return arr + N;
 }
 
@@ -76,9 +69,13 @@ struct has_member_fn_begin_end_t<T, void_t<decltype(*std::declval<T>().begin()),
 
 // Member function overloads.
 template <typename T>
-auto range_begin(T&& rng) FMT_DECLTYPE_RETURN(static_cast<T&&>(rng).begin());
+auto range_begin(T&& rng) -> decltype(static_cast<T&&>(rng).begin()) {
+  return static_cast<T&&>(rng).begin();
+}
 template <typename T>
-auto range_end(T&& rng) FMT_DECLTYPE_RETURN(static_cast<T&&>(rng).end());
+auto range_end(T&& rng) -> decltype(static_cast<T&&>(rng).end()) {
+  return static_cast<T&&>(rng).end();
+}
 
 // ADL overloads. Only participate in overload resolution if member functions
 // are not found.
@@ -115,21 +112,20 @@ struct has_mutable_begin_end<
               // SFINAE properly unless there are distinct types
               int>> : std::true_type {};
 
+template <typename T, typename _ = void> struct is_range_ : std::false_type {};
 template <typename T>
 struct is_range_<T, void>
     : std::integral_constant<bool, (has_const_begin_end<T>::value ||
                                     has_mutable_begin_end<T>::value)> {};
-#  undef FMT_DECLTYPE_RETURN
-#endif
 
 // tuple_size and tuple_element check.
 template <typename T> class is_tuple_like_ {
-  template <typename U>
-  static auto check(U* p) -> decltype(std::tuple_size<U>::value, int());
+  template <typename U, typename V = typename std::remove_cv<U>::type>
+  static auto check(U* p) -> decltype(std::tuple_size<V>::value, 0);
   template <typename> static void check(...);
 
  public:
-  static constexpr const bool value =
+  static constexpr bool value =
       !std::is_void<decltype(check<T>(nullptr))>::value;
 };
 
@@ -163,7 +159,7 @@ using tuple_index_sequence = make_index_sequence<std::tuple_size<T>::value>;
 template <typename T, typename C, bool = is_tuple_like_<T>::value>
 class is_tuple_formattable_ {
  public:
-  static constexpr const bool value = false;
+  static constexpr bool value = false;
 };
 template <typename T, typename C> class is_tuple_formattable_<T, C, true> {
   template <size_t... Is>
@@ -179,7 +175,7 @@ template <typename T, typename C> class is_tuple_formattable_<T, C, true> {
                                        C>::value)...>{}));
 
  public:
-  static constexpr const bool value =
+  static constexpr bool value =
       decltype(check(tuple_index_sequence<T>{}))::value;
 };
 
@@ -217,7 +213,7 @@ template <typename Char, typename... T>
 using result_t = std::tuple<formatter<remove_cvref_t<T>, Char>...>;
 
 using std::get;
-template <typename Tuple, typename Char, std::size_t... Is>
+template <typename Tuple, typename Char, size_t... Is>
 auto get_formatters(index_sequence<Is...>)
     -> result_t<Char, decltype(get<Is>(std::declval<Tuple>()))...>;
 }  // namespace tuple
@@ -228,7 +224,7 @@ template <typename R> struct range_reference_type_impl {
   using type = decltype(*detail::range_begin(std::declval<R&>()));
 };
 
-template <typename T, std::size_t N> struct range_reference_type_impl<T[N]> {
+template <typename T, size_t N> struct range_reference_type_impl<T[N]> {
   using type = T&;
 };
 
@@ -245,14 +241,6 @@ using range_reference_type =
 template <typename Range>
 using uncvref_type = remove_cvref_t<range_reference_type<Range>>;
 
-template <typename Formatter>
-FMT_CONSTEXPR auto maybe_set_debug_format(Formatter& f, bool set)
-    -> decltype(f.set_debug_format(set)) {
-  f.set_debug_format(set);
-}
-template <typename Formatter>
-FMT_CONSTEXPR void maybe_set_debug_format(Formatter&, ...) {}
-
 template <typename T>
 struct range_format_kind_
     : std::integral_constant<range_format,
@@ -266,12 +254,12 @@ template <range_format K>
 using range_format_constant = std::integral_constant<range_format, K>;
 
 // These are not generic lambdas for compatibility with C++11.
-template <typename ParseContext> struct parse_empty_specs {
+template <typename Char> struct parse_empty_specs {
   template <typename Formatter> FMT_CONSTEXPR void operator()(Formatter& f) {
     f.parse(ctx);
     detail::maybe_set_debug_format(f, true);
   }
-  ParseContext& ctx;
+  parse_context<Char>& ctx;
 };
 template <typename FormatContext> struct format_tuple_element {
   using char_type = typename FormatContext::char_type;
@@ -290,14 +278,15 @@ template <typename FormatContext> struct format_tuple_element {
 
 }  // namespace detail
 
+FMT_EXPORT
 template <typename T> struct is_tuple_like {
-  static constexpr const bool value =
+  static constexpr bool value =
       detail::is_tuple_like_<T>::value && !detail::is_range_<T>::value;
 };
 
+FMT_EXPORT
 template <typename T, typename C> struct is_tuple_formattable {
-  static constexpr const bool value =
-      detail::is_tuple_formattable_<T, C>::value;
+  static constexpr bool value = detail::is_tuple_formattable_<T, C>::value;
 };
 
 template <typename Tuple, typename Char>
@@ -327,11 +316,17 @@ struct formatter<Tuple, Char,
     closing_bracket_ = close;
   }
 
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     auto it = ctx.begin();
-    if (it != ctx.end() && *it != '}') report_error("invalid format specifier");
-    detail::for_each(formatters_, detail::parse_empty_specs<ParseContext>{ctx});
+    auto end = ctx.end();
+    if (it != end && detail::to_ascii(*it) == 'n') {
+      ++it;
+      set_brackets({}, {});
+      set_separator({});
+    }
+    if (it != end && *it != '}') report_error("invalid format specifier");
+    ctx.advance_to(it);
+    detail::for_each(formatters_, detail::parse_empty_specs<Char>{ctx});
     return it;
   }
 
@@ -346,44 +341,24 @@ struct formatter<Tuple, Char,
   }
 };
 
+FMT_EXPORT
 template <typename T, typename Char> struct is_range {
-  static constexpr const bool value =
+  static constexpr bool value =
       detail::is_range_<T>::value && !detail::has_to_string_view<T>::value;
 };
 
 namespace detail {
-template <typename Context> struct range_mapper {
-  using mapper = arg_mapper<Context>;
-
-  template <typename T,
-            FMT_ENABLE_IF(has_formatter<remove_cvref_t<T>, Context>::value)>
-  static auto map(T&& value) -> T&& {
-    return static_cast<T&&>(value);
-  }
-  template <typename T,
-            FMT_ENABLE_IF(!has_formatter<remove_cvref_t<T>, Context>::value)>
-  static auto map(T&& value)
-      -> decltype(mapper().map(static_cast<T&&>(value))) {
-    return mapper().map(static_cast<T&&>(value));
-  }
-};
 
 template <typename Char, typename Element>
-using range_formatter_type =
-    formatter<remove_cvref_t<decltype(range_mapper<buffered_context<Char>>{}
-                                          .map(std::declval<Element>()))>,
-              Char>;
+using range_formatter_type = formatter<remove_cvref_t<Element>, Char>;
 
 template <typename R>
 using maybe_const_range =
     conditional_t<has_const_begin_end<R>::value, const R, R>;
 
-// Workaround a bug in MSVC 2015 and earlier.
-#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1910
 template <typename R, typename Char>
 struct is_formattable_delayed
     : is_formattable<uncvref_type<maybe_const_range<R>>, Char> {};
-#endif
 }  // namespace detail
 
 template <typename...> struct conjunction : std::true_type {};
@@ -392,6 +367,7 @@ template <typename P1, typename... Pn>
 struct conjunction<P1, Pn...>
     : conditional_t<bool(P1::value), conjunction<Pn...>, P1> {};
 
+FMT_EXPORT
 template <typename T, typename Char, typename Enable = void>
 struct range_formatter;
 
@@ -415,7 +391,7 @@ struct range_formatter<
     auto buf = basic_memory_buffer<Char>();
     for (; it != end; ++it) buf.push_back(*it);
     auto specs = format_specs();
-    specs.type = presentation_type::debug;
+    specs.set_type(presentation_type::debug);
     return detail::write<Char>(
         out, basic_string_view<Char>(buf.data(), buf.size()), specs);
   }
@@ -443,8 +419,7 @@ struct range_formatter<
     closing_bracket_ = close;
   }
 
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     auto it = ctx.begin();
     auto end = ctx.end();
     detail::maybe_set_debug_format(underlying_, true);
@@ -486,11 +461,10 @@ struct range_formatter<
 
   template <typename R, typename FormatContext>
   auto format(R&& range, FormatContext& ctx) const -> decltype(ctx.out()) {
-    auto mapper = detail::range_mapper<buffered_context<Char>>();
     auto out = ctx.out();
     auto it = detail::range_begin(range);
     auto end = detail::range_end(range);
-    if (is_debug) return write_debug_string(out, it, end);
+    if (is_debug) return write_debug_string(out, std::move(it), end);
 
     out = detail::copy<Char>(opening_bracket_, out);
     int i = 0;
@@ -498,7 +472,7 @@ struct range_formatter<
       if (i > 0) out = detail::copy<Char>(separator_, out);
       ctx.advance_to(out);
       auto&& item = *it;  // Need an lvalue
-      out = underlying_.format(mapper.map(item), ctx);
+      out = underlying_.format(item, ctx);
       ++i;
     }
     out = detail::copy<Char>(closing_bracket_, out);
@@ -521,13 +495,8 @@ struct formatter<
             range_format_kind<R, Char>::value != range_format::disabled &&
             range_format_kind<R, Char>::value != range_format::map &&
             range_format_kind<R, Char>::value != range_format::string &&
-            range_format_kind<R, Char>::value != range_format::debug_string>
-// Workaround a bug in MSVC 2015 and earlier.
-#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1910
-        ,
-        detail::is_formattable_delayed<R, Char>
-#endif
-        >::value>> {
+            range_format_kind<R, Char>::value != range_format::debug_string>,
+        detail::is_formattable_delayed<R, Char>>::value>> {
  private:
   using range_type = detail::maybe_const_range<R>;
   range_formatter<detail::uncvref_type<range_type>, Char> range_formatter_;
@@ -543,8 +512,7 @@ struct formatter<
                                   detail::string_literal<Char, '}'>{});
   }
 
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     return range_formatter_.parse(ctx);
   }
 
@@ -559,7 +527,9 @@ struct formatter<
 template <typename R, typename Char>
 struct formatter<
     R, Char,
-    enable_if_t<range_format_kind<R, Char>::value == range_format::map>> {
+    enable_if_t<conjunction<
+        bool_constant<range_format_kind<R, Char>::value == range_format::map>,
+        detail::is_formattable_delayed<R, Char>>::value>> {
  private:
   using map_type = detail::maybe_const_range<R>;
   using element_type = detail::uncvref_type<map_type>;
@@ -571,8 +541,7 @@ struct formatter<
  public:
   FMT_CONSTEXPR formatter() {}
 
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     auto it = ctx.begin();
     auto end = ctx.end();
     if (it != end) {
@@ -586,7 +555,7 @@ struct formatter<
       }
       ctx.advance_to(it);
     }
-    detail::for_each(formatters_, detail::parse_empty_specs<ParseContext>{ctx});
+    detail::for_each(formatters_, detail::parse_empty_specs<Char>{ctx});
     return it;
   }
 
@@ -596,12 +565,11 @@ struct formatter<
     basic_string_view<Char> open = detail::string_literal<Char, '{'>{};
     if (!no_delimiters_) out = detail::copy<Char>(open, out);
     int i = 0;
-    auto mapper = detail::range_mapper<buffered_context<Char>>();
     basic_string_view<Char> sep = detail::string_literal<Char, ',', ' '>{};
     for (auto&& value : map) {
       if (i > 0) out = detail::copy<Char>(sep, out);
       ctx.advance_to(out);
-      detail::for_each2(formatters_, mapper.map(value),
+      detail::for_each2(formatters_, value,
                         detail::format_tuple_element<FormatContext>{
                             0, ctx, detail::string_literal<Char, ':', ' '>{}});
       ++i;
@@ -631,8 +599,7 @@ struct formatter<
   formatter<string_type, Char> underlying_;
 
  public:
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     return underlying_.parse(ctx);
   }
 
@@ -673,22 +640,22 @@ struct formatter<join_view<It, Sentinel, Char>, Char> {
 #endif
   formatter<remove_cvref_t<value_type>, Char> value_formatter_;
 
-  using view_ref = conditional_t<std::is_copy_constructible<It>::value,
-                                 const join_view<It, Sentinel, Char>&,
-                                 join_view<It, Sentinel, Char>&&>;
+  using view = conditional_t<std::is_copy_constructible<It>::value,
+                             const join_view<It, Sentinel, Char>,
+                             join_view<It, Sentinel, Char>>;
 
  public:
   using nonlocking = void;
 
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> const Char* {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     return value_formatter_.parse(ctx);
   }
 
   template <typename FormatContext>
-  auto format(view_ref& value, FormatContext& ctx) const
-      -> decltype(ctx.out()) {
-    auto it = std::forward<view_ref>(value).begin;
+  auto format(view& value, FormatContext& ctx) const -> decltype(ctx.out()) {
+    using iter =
+        conditional_t<std::is_copy_constructible<view>::value, It, It&>;
+    iter it = value.begin;
     auto out = ctx.out();
     if (it == value.end) return out;
     out = value_formatter_.format(*it, ctx);
@@ -703,39 +670,12 @@ struct formatter<join_view<It, Sentinel, Char>, Char> {
   }
 };
 
-/// Returns a view that formats the iterator range `[begin, end)` with elements
-/// separated by `sep`.
-template <typename It, typename Sentinel>
-auto join(It begin, Sentinel end, string_view sep) -> join_view<It, Sentinel> {
-  return {std::move(begin), end, sep};
-}
-
-/**
- * Returns a view that formats `range` with elements separated by `sep`.
- *
- * **Example**:
- *
- *     auto v = std::vector<int>{1, 2, 3};
- *     fmt::print("{}", fmt::join(v, ", "));
- *     // Output: 1, 2, 3
- *
- * `fmt::join` applies passed format specifiers to the range elements:
- *
- *     fmt::print("{:02}", fmt::join(v, ", "));
- *     // Output: 01, 02, 03
- */
-template <typename Range>
-auto join(Range&& r, string_view sep)
-    -> join_view<decltype(detail::range_begin(r)),
-                 decltype(detail::range_end(r))> {
-  return {detail::range_begin(r), detail::range_end(r), sep};
-}
-
-template <typename Char, typename... T> struct tuple_join_view : detail::view {
-  const std::tuple<T...>& tuple;
+FMT_EXPORT
+template <typename Tuple, typename Char> struct tuple_join_view : detail::view {
+  const Tuple& tuple;
   basic_string_view<Char> sep;
 
-  tuple_join_view(const std::tuple<T...>& t, basic_string_view<Char> s)
+  tuple_join_view(const Tuple& t, basic_string_view<Char> s)
       : tuple(t), sep{s} {}
 };
 
@@ -746,37 +686,36 @@ template <typename Char, typename... T> struct tuple_join_view : detail::view {
 #  define FMT_TUPLE_JOIN_SPECIFIERS 0
 #endif
 
-template <typename Char, typename... T>
-struct formatter<tuple_join_view<Char, T...>, Char> {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return do_parse(ctx, std::integral_constant<size_t, sizeof...(T)>());
+template <typename Tuple, typename Char>
+struct formatter<tuple_join_view<Tuple, Char>, Char,
+                 enable_if_t<is_tuple_like<Tuple>::value>> {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+    return do_parse(ctx, std::tuple_size<Tuple>());
   }
 
   template <typename FormatContext>
-  auto format(const tuple_join_view<Char, T...>& value,
+  auto format(const tuple_join_view<Tuple, Char>& value,
               FormatContext& ctx) const -> typename FormatContext::iterator {
-    return do_format(value, ctx,
-                     std::integral_constant<size_t, sizeof...(T)>());
+    return do_format(value, ctx, std::tuple_size<Tuple>());
   }
 
  private:
-  std::tuple<formatter<typename std::decay<T>::type, Char>...> formatters_;
+  decltype(detail::tuple::get_formatters<Tuple, Char>(
+      detail::tuple_index_sequence<Tuple>())) formatters_;
 
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto do_parse(ParseContext& ctx,
+  FMT_CONSTEXPR auto do_parse(parse_context<Char>& ctx,
                               std::integral_constant<size_t, 0>)
-      -> decltype(ctx.begin()) {
+      -> const Char* {
     return ctx.begin();
   }
 
-  template <typename ParseContext, size_t N>
-  FMT_CONSTEXPR auto do_parse(ParseContext& ctx,
+  template <size_t N>
+  FMT_CONSTEXPR auto do_parse(parse_context<Char>& ctx,
                               std::integral_constant<size_t, N>)
-      -> decltype(ctx.begin()) {
+      -> const Char* {
     auto end = ctx.begin();
 #if FMT_TUPLE_JOIN_SPECIFIERS
-    end = std::get<sizeof...(T) - N>(formatters_).parse(ctx);
+    end = std::get<std::tuple_size<Tuple>::value - N>(formatters_).parse(ctx);
     if (N > 1) {
       auto end1 = do_parse(ctx, std::integral_constant<size_t, N - 1>());
       if (end != end1)
@@ -787,18 +726,20 @@ struct formatter<tuple_join_view<Char, T...>, Char> {
   }
 
   template <typename FormatContext>
-  auto do_format(const tuple_join_view<Char, T...>&, FormatContext& ctx,
+  auto do_format(const tuple_join_view<Tuple, Char>&, FormatContext& ctx,
                  std::integral_constant<size_t, 0>) const ->
       typename FormatContext::iterator {
     return ctx.out();
   }
 
   template <typename FormatContext, size_t N>
-  auto do_format(const tuple_join_view<Char, T...>& value, FormatContext& ctx,
+  auto do_format(const tuple_join_view<Tuple, Char>& value, FormatContext& ctx,
                  std::integral_constant<size_t, N>) const ->
       typename FormatContext::iterator {
-    auto out = std::get<sizeof...(T) - N>(formatters_)
-                   .format(std::get<sizeof...(T) - N>(value.tuple), ctx);
+    using std::get;
+    auto out =
+        std::get<std::tuple_size<Tuple>::value - N>(formatters_)
+            .format(get<std::tuple_size<Tuple>::value - N>(value.tuple), ctx);
     if (N <= 1) return out;
     out = detail::copy<Char>(value.sep, out);
     ctx.advance_to(out);
@@ -814,7 +755,7 @@ template <typename T> class is_container_adaptor_like {
   template <typename> static void check(...);
 
  public:
-  static constexpr const bool value =
+  static constexpr bool value =
       !std::is_void<decltype(check<T>(nullptr))>::value;
 };
 
@@ -834,30 +775,58 @@ struct formatter<
     : formatter<detail::all<typename T::container_type>, Char> {
   using all = detail::all<typename T::container_type>;
   template <typename FormatContext>
-  auto format(const T& t, FormatContext& ctx) const -> decltype(ctx.out()) {
+  auto format(const T& value, FormatContext& ctx) const -> decltype(ctx.out()) {
     struct getter : T {
-      static auto get(const T& t) -> all {
-        return {t.*(&getter::c)};  // Access c through the derived class.
+      static auto get(const T& v) -> all {
+        return {v.*(&getter::c)};  // Access c through the derived class.
       }
     };
-    return formatter<all>::format(getter::get(t), ctx);
+    return formatter<all>::format(getter::get(value), ctx);
   }
 };
 
 FMT_BEGIN_EXPORT
 
+/// Returns a view that formats the iterator range `[begin, end)` with elements
+/// separated by `sep`.
+template <typename It, typename Sentinel>
+auto join(It begin, Sentinel end, string_view sep) -> join_view<It, Sentinel> {
+  return {std::move(begin), end, sep};
+}
+
+/**
+ * Returns a view that formats `range` with elements separated by `sep`.
+ *
+ * **Example**:
+ *
+ *     auto v = std::vector<int>{1, 2, 3};
+ *     fmt::print("{}", fmt::join(v, ", "));
+ *     // Output: 1, 2, 3
+ *
+ * `fmt::join` applies passed format specifiers to the range elements:
+ *
+ *     fmt::print("{:02}", fmt::join(v, ", "));
+ *     // Output: 01, 02, 03
+ */
+template <typename Range, FMT_ENABLE_IF(!is_tuple_like<Range>::value)>
+auto join(Range&& r, string_view sep)
+    -> join_view<decltype(detail::range_begin(r)),
+                 decltype(detail::range_end(r))> {
+  return {detail::range_begin(r), detail::range_end(r), sep};
+}
+
 /**
  * Returns an object that formats `std::tuple` with elements separated by `sep`.
  *
  * **Example**:
  *
- *     auto t = std::tuple<int, char>{1, 'a'};
+ *     auto t = std::tuple<int, char>(1, 'a');
  *     fmt::print("{}", fmt::join(t, ", "));
  *     // Output: 1, a
  */
-template <typename... T>
-FMT_CONSTEXPR auto join(const std::tuple<T...>& tuple, string_view sep)
-    -> tuple_join_view<char, T...> {
+template <typename Tuple, FMT_ENABLE_IF(is_tuple_like<Tuple>::value)>
+FMT_CONSTEXPR auto join(const Tuple& tuple FMT_LIFETIMEBOUND, string_view sep)
+    -> tuple_join_view<Tuple, char> {
   return {tuple, sep};
 }
 
diff --git a/contrib/fmt/include/fmt/std.h b/contrib/fmt/include/fmt/std.h
index 01a61cee61..184c6d26d6 100644
--- a/contrib/fmt/include/fmt/std.h
+++ b/contrib/fmt/include/fmt/std.h
@@ -15,18 +15,18 @@
 #  include <atomic>
 #  include <bitset>
 #  include <complex>
-#  include <cstdlib>
 #  include <exception>
+#  include <functional>  // std::reference_wrapper
 #  include <memory>
 #  include <thread>
 #  include <type_traits>
-#  include <typeinfo>
-#  include <utility>
-#  include <vector>
+#  include <typeinfo>  // std::type_info
+#  include <utility>   // std::make_index_sequence
 
 // Check FMT_CPLUSPLUS to suppress a bogus warning in MSVC.
 #  if FMT_CPLUSPLUS >= 201703L
-#    if FMT_HAS_INCLUDE(<filesystem>)
+#    if FMT_HAS_INCLUDE(<filesystem>) && \
+        (!defined(FMT_CPP_LIB_FILESYSTEM) || FMT_CPP_LIB_FILESYSTEM != 0)
 #      include <filesystem>
 #    endif
 #    if FMT_HAS_INCLUDE(<variant>)
@@ -60,28 +60,27 @@
 #  endif
 #endif
 
-// For older Xcode versions, __cpp_lib_xxx flags are inaccurately defined.
-#ifndef FMT_CPP_LIB_FILESYSTEM
-#  ifdef __cpp_lib_filesystem
-#    define FMT_CPP_LIB_FILESYSTEM __cpp_lib_filesystem
-#  else
-#    define FMT_CPP_LIB_FILESYSTEM 0
-#  endif
+#ifdef FMT_CPP_LIB_FILESYSTEM
+// Use the provided definition.
+#elif defined(__cpp_lib_filesystem)
+#  define FMT_CPP_LIB_FILESYSTEM __cpp_lib_filesystem
+#else
+#  define FMT_CPP_LIB_FILESYSTEM 0
 #endif
 
-#ifndef FMT_CPP_LIB_VARIANT
-#  ifdef __cpp_lib_variant
-#    define FMT_CPP_LIB_VARIANT __cpp_lib_variant
-#  else
-#    define FMT_CPP_LIB_VARIANT 0
-#  endif
+#ifdef FMT_CPP_LIB_VARIANT
+// Use the provided definition.
+#elif defined(__cpp_lib_variant)
+#  define FMT_CPP_LIB_VARIANT __cpp_lib_variant
+#else
+#  define FMT_CPP_LIB_VARIANT 0
 #endif
 
-#if FMT_CPP_LIB_FILESYSTEM
 FMT_BEGIN_NAMESPACE
-
 namespace detail {
 
+#if FMT_CPP_LIB_FILESYSTEM
+
 template <typename Char, typename PathChar>
 auto get_path_string(const std::filesystem::path& p,
                      const std::basic_string<PathChar>& native) {
@@ -109,9 +108,180 @@ void write_escaped_path(basic_memory_buffer<Char>& quoted,
   }
 }
 
+#endif  // FMT_CPP_LIB_FILESYSTEM
+
+#if defined(__cpp_lib_expected) || FMT_CPP_LIB_VARIANT
+
+template <typename Char, typename OutputIt, typename T, typename FormatContext>
+auto write_escaped_alternative(OutputIt out, const T& v, FormatContext& ctx)
+    -> OutputIt {
+  if constexpr (has_to_string_view<T>::value)
+    return write_escaped_string<Char>(out, detail::to_string_view(v));
+  if constexpr (std::is_same_v<T, Char>) return write_escaped_char(out, v);
+
+  formatter<std::remove_cv_t<T>, Char> underlying;
+  maybe_set_debug_format(underlying, true);
+  return underlying.format(v, ctx);
+}
+#endif
+
+#if FMT_CPP_LIB_VARIANT
+
+template <typename> struct is_variant_like_ : std::false_type {};
+template <typename... Types>
+struct is_variant_like_<std::variant<Types...>> : std::true_type {};
+
+template <typename Variant, typename Char> class is_variant_formattable {
+  template <size_t... Is>
+  static auto check(std::index_sequence<Is...>) -> std::conjunction<
+      is_formattable<std::variant_alternative_t<Is, Variant>, Char>...>;
+
+ public:
+  static constexpr bool value = decltype(check(
+      std::make_index_sequence<std::variant_size<Variant>::value>()))::value;
+};
+
+#endif  // FMT_CPP_LIB_VARIANT
+
+#if FMT_USE_RTTI
+inline auto normalize_libcxx_inline_namespaces(string_view demangled_name_view,
+                                               char* begin) -> string_view {
+  // Normalization of stdlib inline namespace names.
+  // libc++ inline namespaces.
+  //  std::__1::*       -> std::*
+  //  std::__1::__fs::* -> std::*
+  // libstdc++ inline namespaces.
+  //  std::__cxx11::*             -> std::*
+  //  std::filesystem::__cxx11::* -> std::filesystem::*
+  if (demangled_name_view.starts_with("std::")) {
+    char* to = begin + 5;  // std::
+    for (const char *from = to, *end = begin + demangled_name_view.size();
+         from < end;) {
+      // This is safe, because demangled_name is NUL-terminated.
+      if (from[0] == '_' && from[1] == '_') {
+        const char* next = from + 1;
+        while (next < end && *next != ':') next++;
+        if (next[0] == ':' && next[1] == ':') {
+          from = next + 2;
+          continue;
+        }
+      }
+      *to++ = *from++;
+    }
+    demangled_name_view = {begin, detail::to_unsigned(to - begin)};
+  }
+  return demangled_name_view;
+}
+
+template <class OutputIt>
+auto normalize_msvc_abi_name(string_view abi_name_view, OutputIt out)
+    -> OutputIt {
+  const string_view demangled_name(abi_name_view);
+  for (size_t i = 0; i < demangled_name.size(); ++i) {
+    auto sub = demangled_name;
+    sub.remove_prefix(i);
+    if (sub.starts_with("enum ")) {
+      i += 4;
+      continue;
+    }
+    if (sub.starts_with("class ") || sub.starts_with("union ")) {
+      i += 5;
+      continue;
+    }
+    if (sub.starts_with("struct ")) {
+      i += 6;
+      continue;
+    }
+    if (*sub.begin() != ' ') *out++ = *sub.begin();
+  }
+  return out;
+}
+
+template <typename OutputIt>
+auto write_demangled_name(OutputIt out, const std::type_info& ti) -> OutputIt {
+#  ifdef FMT_HAS_ABI_CXA_DEMANGLE
+  int status = 0;
+  size_t size = 0;
+  std::unique_ptr<char, void (*)(void*)> demangled_name_ptr(
+      abi::__cxa_demangle(ti.name(), nullptr, &size, &status), &free);
+
+  string_view demangled_name_view;
+  if (demangled_name_ptr) {
+    demangled_name_view = normalize_libcxx_inline_namespaces(
+        demangled_name_ptr.get(), demangled_name_ptr.get());
+  } else {
+    demangled_name_view = string_view(ti.name());
+  }
+  return detail::write_bytes<char>(out, demangled_name_view);
+#  elif FMT_MSC_VERSION && defined(_MSVC_STL_UPDATE)
+  return normalize_msvc_abi_name(ti.name(), out);
+#  elif FMT_MSC_VERSION && defined(_LIBCPP_VERSION)
+  const string_view demangled_name = ti.name();
+  std::string name_copy(demangled_name.size(), '\0');
+  // normalize_msvc_abi_name removes class, struct, union etc that MSVC has in
+  // front of types
+  name_copy.erase(normalize_msvc_abi_name(demangled_name, name_copy.begin()),
+                  name_copy.end());
+  // normalize_libcxx_inline_namespaces removes the inline __1, __2, etc
+  // namespaces libc++ uses for ABI versioning On MSVC ABI + libc++
+  // environments, we need to eliminate both of them.
+  const string_view normalized_name =
+      normalize_libcxx_inline_namespaces(name_copy, name_copy.data());
+  return detail::write_bytes<char>(out, normalized_name);
+#  else
+  return detail::write_bytes<char>(out, string_view(ti.name()));
+#  endif
+}
+
+#endif  // FMT_USE_RTTI
+
+template <typename T, typename Enable = void>
+struct has_flip : std::false_type {};
+
+template <typename T>
+struct has_flip<T, void_t<decltype(std::declval<T>().flip())>>
+    : std::true_type {};
+
+template <typename T> struct is_bit_reference_like {
+  static constexpr bool value = std::is_convertible<T, bool>::value &&
+                                std::is_nothrow_assignable<T, bool>::value &&
+                                has_flip<T>::value;
+};
+
+// Workaround for libc++ incompatibility with C++ standard.
+// According to the Standard, `bitset::operator[] const` returns bool.
+#if defined(_LIBCPP_VERSION) && !defined(FMT_IMPORT_STD)
+template <typename C>
+struct is_bit_reference_like<std::__bit_const_reference<C>> {
+  static constexpr bool value = true;
+};
+#endif
+
+template <typename T, typename Enable = void>
+struct has_format_as : std::false_type {};
+template <typename T>
+struct has_format_as<T, void_t<decltype(format_as(std::declval<const T&>()))>>
+    : std::true_type {};
+
+template <typename T, typename Enable = void>
+struct has_format_as_member : std::false_type {};
+template <typename T>
+struct has_format_as_member<
+    T, void_t<decltype(formatter<T>::format_as(std::declval<const T&>()))>>
+    : std::true_type {};
+
 }  // namespace detail
 
-FMT_EXPORT
+template <typename T, typename Deleter>
+auto ptr(const std::unique_ptr<T, Deleter>& p) -> const void* {
+  return p.get();
+}
+template <typename T> auto ptr(const std::shared_ptr<T>& p) -> const void* {
+  return p.get();
+}
+
+#if FMT_CPP_LIB_FILESYSTEM
+
 template <typename Char> struct formatter<std::filesystem::path, Char> {
  private:
   format_specs specs_;
@@ -122,14 +292,16 @@ template <typename Char> struct formatter<std::filesystem::path, Char> {
  public:
   FMT_CONSTEXPR void set_debug_format(bool set = true) { debug_ = set; }
 
-  template <typename ParseContext> FMT_CONSTEXPR auto parse(ParseContext& ctx) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) {
     auto it = ctx.begin(), end = ctx.end();
     if (it == end) return it;
 
     it = detail::parse_align(it, end, specs_);
     if (it == end) return it;
 
-    it = detail::parse_dynamic_spec(it, end, specs_.width, width_ref_, ctx);
+    Char c = *it;
+    if ((c >= '0' && c <= '9') || c == '{')
+      it = detail::parse_width(it, end, specs_, width_ref_, ctx);
     if (it != end && *it == '?') {
       debug_ = true;
       ++it;
@@ -145,8 +317,8 @@ template <typename Char> struct formatter<std::filesystem::path, Char> {
         !path_type_ ? p.native()
                     : p.generic_string<std::filesystem::path::value_type>();
 
-    detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref_,
-                                                       ctx);
+    detail::handle_dynamic_spec(specs.dynamic_width(), specs.width, width_ref_,
+                                ctx);
     if (!debug_) {
       auto s = detail::get_path_string<Char>(p, path_string);
       return detail::write(ctx.out(), basic_string_view<Char>(s), specs);
@@ -174,24 +346,20 @@ class path : public std::filesystem::path {
   auto generic_system_string() const -> std::string { return generic_string(); }
 };
 
-FMT_END_NAMESPACE
 #endif  // FMT_CPP_LIB_FILESYSTEM
 
-FMT_BEGIN_NAMESPACE
-FMT_EXPORT
-template <std::size_t N, typename Char>
-struct formatter<std::bitset<N>, Char> : nested_formatter<string_view> {
+template <size_t N, typename Char>
+struct formatter<std::bitset<N>, Char>
+    : nested_formatter<basic_string_view<Char>, Char> {
  private:
-  // Functor because C++11 doesn't support generic lambdas.
+  // This is a functor because C++11 doesn't support generic lambdas.
   struct writer {
     const std::bitset<N>& bs;
 
     template <typename OutputIt>
     FMT_CONSTEXPR auto operator()(OutputIt out) -> OutputIt {
-      for (auto pos = N; pos > 0; --pos) {
+      for (auto pos = N; pos > 0; --pos)
         out = detail::write<Char>(out, bs[pos - 1] ? Char('1') : Char('0'));
-      }
-
       return out;
     }
   };
@@ -200,41 +368,28 @@ struct formatter<std::bitset<N>, Char> : nested_formatter<string_view> {
   template <typename FormatContext>
   auto format(const std::bitset<N>& bs, FormatContext& ctx) const
       -> decltype(ctx.out()) {
-    return write_padded(ctx, writer{bs});
+    return this->write_padded(ctx, writer{bs});
   }
 };
 
-FMT_EXPORT
 template <typename Char>
 struct formatter<std::thread::id, Char> : basic_ostream_formatter<Char> {};
-FMT_END_NAMESPACE
 
 #ifdef __cpp_lib_optional
-FMT_BEGIN_NAMESPACE
-FMT_EXPORT
 template <typename T, typename Char>
 struct formatter<std::optional<T>, Char,
                  std::enable_if_t<is_formattable<T, Char>::value>> {
  private:
-  formatter<T, Char> underlying_;
+  formatter<std::remove_cv_t<T>, Char> underlying_;
   static constexpr basic_string_view<Char> optional =
       detail::string_literal<Char, 'o', 'p', 't', 'i', 'o', 'n', 'a', 'l',
                              '('>{};
   static constexpr basic_string_view<Char> none =
       detail::string_literal<Char, 'n', 'o', 'n', 'e'>{};
 
-  template <class U>
-  FMT_CONSTEXPR static auto maybe_set_debug_format(U& u, bool set)
-      -> decltype(u.set_debug_format(set)) {
-    u.set_debug_format(set);
-  }
-
-  template <class U>
-  FMT_CONSTEXPR static void maybe_set_debug_format(U&, ...) {}
-
  public:
-  template <typename ParseContext> FMT_CONSTEXPR auto parse(ParseContext& ctx) {
-    maybe_set_debug_format(underlying_, true);
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) {
+    detail::maybe_set_debug_format(underlying_, true);
     return underlying_.parse(ctx);
   }
 
@@ -250,37 +405,15 @@ struct formatter<std::optional<T>, Char,
     return detail::write(out, ')');
   }
 };
-FMT_END_NAMESPACE
 #endif  // __cpp_lib_optional
 
-#if defined(__cpp_lib_expected) || FMT_CPP_LIB_VARIANT
-
-FMT_BEGIN_NAMESPACE
-namespace detail {
-
-template <typename Char, typename OutputIt, typename T>
-auto write_escaped_alternative(OutputIt out, const T& v) -> OutputIt {
-  if constexpr (has_to_string_view<T>::value)
-    return write_escaped_string<Char>(out, detail::to_string_view(v));
-  if constexpr (std::is_same_v<T, Char>) return write_escaped_char(out, v);
-  return write<Char>(out, v);
-}
-
-}  // namespace detail
-
-FMT_END_NAMESPACE
-#endif
-
 #ifdef __cpp_lib_expected
-FMT_BEGIN_NAMESPACE
-
-FMT_EXPORT
 template <typename T, typename E, typename Char>
 struct formatter<std::expected<T, E>, Char,
-                 std::enable_if_t<is_formattable<T, Char>::value &&
+                 std::enable_if_t<(std::is_void<T>::value ||
+                                   is_formattable<T, Char>::value) &&
                                   is_formattable<E, Char>::value>> {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     return ctx.begin();
   }
 
@@ -291,25 +424,21 @@ struct formatter<std::expected<T, E>, Char,
 
     if (value.has_value()) {
       out = detail::write<Char>(out, "expected(");
-      out = detail::write_escaped_alternative<Char>(out, value.value());
+      if constexpr (!std::is_void<T>::value)
+        out = detail::write_escaped_alternative<Char>(out, *value, ctx);
     } else {
       out = detail::write<Char>(out, "unexpected(");
-      out = detail::write_escaped_alternative<Char>(out, value.error());
+      out = detail::write_escaped_alternative<Char>(out, value.error(), ctx);
     }
     *out++ = ')';
     return out;
   }
 };
-FMT_END_NAMESPACE
 #endif  // __cpp_lib_expected
 
 #ifdef __cpp_lib_source_location
-FMT_BEGIN_NAMESPACE
-FMT_EXPORT
 template <> struct formatter<std::source_location> {
-  template <typename ParseContext> FMT_CONSTEXPR auto parse(ParseContext& ctx) {
-    return ctx.begin();
-  }
+  FMT_CONSTEXPR auto parse(parse_context<>& ctx) { return ctx.begin(); }
 
   template <typename FormatContext>
   auto format(const std::source_location& loc, FormatContext& ctx) const
@@ -325,48 +454,16 @@ template <> struct formatter<std::source_location> {
     return out;
   }
 };
-FMT_END_NAMESPACE
 #endif
 
 #if FMT_CPP_LIB_VARIANT
-FMT_BEGIN_NAMESPACE
-namespace detail {
-
-template <typename T>
-using variant_index_sequence =
-    std::make_index_sequence<std::variant_size<T>::value>;
-
-template <typename> struct is_variant_like_ : std::false_type {};
-template <typename... Types>
-struct is_variant_like_<std::variant<Types...>> : std::true_type {};
-
-// formattable element check.
-template <typename T, typename C> class is_variant_formattable_ {
-  template <std::size_t... Is>
-  static std::conjunction<
-      is_formattable<std::variant_alternative_t<Is, T>, C>...>
-      check(std::index_sequence<Is...>);
-
- public:
-  static constexpr const bool value =
-      decltype(check(variant_index_sequence<T>{}))::value;
-};
-
-}  // namespace detail
 
 template <typename T> struct is_variant_like {
-  static constexpr const bool value = detail::is_variant_like_<T>::value;
+  static constexpr bool value = detail::is_variant_like_<T>::value;
 };
 
-template <typename T, typename C> struct is_variant_formattable {
-  static constexpr const bool value =
-      detail::is_variant_formattable_<T, C>::value;
-};
-
-FMT_EXPORT
 template <typename Char> struct formatter<std::monostate, Char> {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     return ctx.begin();
   }
 
@@ -377,14 +474,12 @@ template <typename Char> struct formatter<std::monostate, Char> {
   }
 };
 
-FMT_EXPORT
 template <typename Variant, typename Char>
-struct formatter<
-    Variant, Char,
-    std::enable_if_t<std::conjunction_v<
-        is_variant_like<Variant>, is_variant_formattable<Variant, Char>>>> {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+struct formatter<Variant, Char,
+                 std::enable_if_t<std::conjunction_v<
+                     is_variant_like<Variant>,
+                     detail::is_variant_formattable<Variant, Char>>>> {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     return ctx.begin();
   }
 
@@ -397,7 +492,7 @@ struct formatter<
     FMT_TRY {
       std::visit(
           [&](const auto& v) {
-            out = detail::write_escaped_alternative<Char>(out, v);
+            out = detail::write_escaped_alternative<Char>(out, v, ctx);
           },
           value);
     }
@@ -408,128 +503,87 @@ struct formatter<
     return out;
   }
 };
-FMT_END_NAMESPACE
+
 #endif  // FMT_CPP_LIB_VARIANT
 
-FMT_BEGIN_NAMESPACE
-FMT_EXPORT
-template <typename Char> struct formatter<std::error_code, Char> {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
+template <> struct formatter<std::error_code> {
+ private:
+  format_specs specs_;
+  detail::arg_ref<char> width_ref_;
+  bool debug_ = false;
 
-  template <typename FormatContext>
-  FMT_CONSTEXPR auto format(const std::error_code& ec, FormatContext& ctx) const
-      -> decltype(ctx.out()) {
-    auto out = ctx.out();
-    out = detail::write_bytes<Char>(out, ec.category().name(), format_specs());
-    out = detail::write<Char>(out, Char(':'));
-    out = detail::write<Char>(out, ec.value());
-    return out;
-  }
-};
+ public:
+  FMT_CONSTEXPR void set_debug_format(bool set = true) { debug_ = set; }
 
-#if FMT_USE_RTTI
-namespace detail {
+  FMT_CONSTEXPR auto parse(parse_context<>& ctx) -> const char* {
+    auto it = ctx.begin(), end = ctx.end();
+    if (it == end) return it;
 
-template <typename Char, typename OutputIt>
-auto write_demangled_name(OutputIt out, const std::type_info& ti) -> OutputIt {
-#  ifdef FMT_HAS_ABI_CXA_DEMANGLE
-  int status = 0;
-  std::size_t size = 0;
-  std::unique_ptr<char, void (*)(void*)> demangled_name_ptr(
-      abi::__cxa_demangle(ti.name(), nullptr, &size, &status), &std::free);
+    it = detail::parse_align(it, end, specs_);
 
-  string_view demangled_name_view;
-  if (demangled_name_ptr) {
-    demangled_name_view = demangled_name_ptr.get();
-
-    // Normalization of stdlib inline namespace names.
-    // libc++ inline namespaces.
-    //  std::__1::*       -> std::*
-    //  std::__1::__fs::* -> std::*
-    // libstdc++ inline namespaces.
-    //  std::__cxx11::*             -> std::*
-    //  std::filesystem::__cxx11::* -> std::filesystem::*
-    if (demangled_name_view.starts_with("std::")) {
-      char* begin = demangled_name_ptr.get();
-      char* to = begin + 5;  // std::
-      for (char *from = to, *end = begin + demangled_name_view.size();
-           from < end;) {
-        // This is safe, because demangled_name is NUL-terminated.
-        if (from[0] == '_' && from[1] == '_') {
-          char* next = from + 1;
-          while (next < end && *next != ':') next++;
-          if (next[0] == ':' && next[1] == ':') {
-            from = next + 2;
-            continue;
-          }
-        }
-        *to++ = *from++;
-      }
-      demangled_name_view = {begin, detail::to_unsigned(to - begin)};
+    char c = *it;
+    if (it != end && ((c >= '0' && c <= '9') || c == '{'))
+      it = detail::parse_width(it, end, specs_, width_ref_, ctx);
+
+    if (it != end && *it == '?') {
+      debug_ = true;
+      ++it;
     }
-  } else {
-    demangled_name_view = string_view(ti.name());
+    if (it != end && *it == 's') {
+      specs_.set_type(presentation_type::string);
+      ++it;
+    }
+    return it;
   }
-  return detail::write_bytes<Char>(out, demangled_name_view);
-#  elif FMT_MSC_VERSION
-  const string_view demangled_name(ti.name());
-  for (std::size_t i = 0; i < demangled_name.size(); ++i) {
-    auto sub = demangled_name;
-    sub.remove_prefix(i);
-    if (sub.starts_with("enum ")) {
-      i += 4;
-      continue;
+
+  template <typename FormatContext>
+  FMT_CONSTEXPR20 auto format(const std::error_code& ec,
+                              FormatContext& ctx) const -> decltype(ctx.out()) {
+    auto specs = specs_;
+    detail::handle_dynamic_spec(specs.dynamic_width(), specs.width, width_ref_,
+                                ctx);
+    auto buf = memory_buffer();
+    if (specs_.type() == presentation_type::string) {
+      buf.append(ec.message());
+    } else {
+      buf.append(string_view(ec.category().name()));
+      buf.push_back(':');
+      detail::write<char>(appender(buf), ec.value());
     }
-    if (sub.starts_with("class ") || sub.starts_with("union ")) {
-      i += 5;
-      continue;
+    auto quoted = memory_buffer();
+    auto str = string_view(buf.data(), buf.size());
+    if (debug_) {
+      detail::write_escaped_string<char>(std::back_inserter(quoted), str);
+      str = string_view(quoted.data(), quoted.size());
     }
-    if (sub.starts_with("struct ")) {
-      i += 6;
-      continue;
-    }
-    if (*sub.begin() != ' ') *out++ = *sub.begin();
+    return detail::write<char>(ctx.out(), str, specs);
   }
-  return out;
-#  else
-  return detail::write_bytes<Char>(out, string_view(ti.name()));
-#  endif
-}
-
-}  // namespace detail
+};
 
-FMT_EXPORT
-template <typename Char>
-struct formatter<std::type_info, Char  // DEPRECATED! Mixing code unit types.
-                 > {
+#if FMT_USE_RTTI
+template <> struct formatter<std::type_info> {
  public:
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<>& ctx) -> const char* {
     return ctx.begin();
   }
 
   template <typename Context>
   auto format(const std::type_info& ti, Context& ctx) const
       -> decltype(ctx.out()) {
-    return detail::write_demangled_name<Char>(ctx.out(), ti);
+    return detail::write_demangled_name(ctx.out(), ti);
   }
 };
-#endif
+#endif  // FMT_USE_RTTI
 
-FMT_EXPORT
-template <typename T, typename Char>
+template <typename T>
 struct formatter<
-    T, Char,  // DEPRECATED! Mixing code unit types.
+    T, char,
     typename std::enable_if<std::is_base_of<std::exception, T>::value>::type> {
  private:
   bool with_typename_ = false;
 
  public:
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(parse_context<>& ctx) -> const char* {
     auto it = ctx.begin();
     auto end = ctx.end();
     if (it == end || *it == '}') return it;
@@ -546,47 +600,18 @@ struct formatter<
     auto out = ctx.out();
 #if FMT_USE_RTTI
     if (with_typename_) {
-      out = detail::write_demangled_name<Char>(out, typeid(ex));
+      out = detail::write_demangled_name(out, typeid(ex));
       *out++ = ':';
       *out++ = ' ';
     }
 #endif
-    return detail::write_bytes<Char>(out, string_view(ex.what()));
+    return detail::write_bytes<char>(out, string_view(ex.what()));
   }
 };
 
-namespace detail {
-
-template <typename T, typename Enable = void>
-struct has_flip : std::false_type {};
-
-template <typename T>
-struct has_flip<T, void_t<decltype(std::declval<T>().flip())>>
-    : std::true_type {};
-
-template <typename T> struct is_bit_reference_like {
-  static constexpr const bool value =
-      std::is_convertible<T, bool>::value &&
-      std::is_nothrow_assignable<T, bool>::value && has_flip<T>::value;
-};
-
-#ifdef _LIBCPP_VERSION
-
-// Workaround for libc++ incompatibility with C++ standard.
-// According to the Standard, `bitset::operator[] const` returns bool.
-template <typename C>
-struct is_bit_reference_like<std::__bit_const_reference<C>> {
-  static constexpr const bool value = true;
-};
-
-#endif
-
-}  // namespace detail
-
 // We can't use std::vector<bool, Allocator>::reference and
 // std::bitset<N>::reference because the compiler can't deduce Allocator and N
 // in partial specialization.
-FMT_EXPORT
 template <typename BitRef, typename Char>
 struct formatter<BitRef, Char,
                  enable_if_t<detail::is_bit_reference_like<BitRef>::value>>
@@ -598,15 +623,6 @@ struct formatter<BitRef, Char,
   }
 };
 
-template <typename T, typename Deleter>
-auto ptr(const std::unique_ptr<T, Deleter>& p) -> const void* {
-  return p.get();
-}
-template <typename T> auto ptr(const std::shared_ptr<T>& p) -> const void* {
-  return p.get();
-}
-
-FMT_EXPORT
 template <typename T, typename Char>
 struct formatter<std::atomic<T>, Char,
                  enable_if_t<is_formattable<T, Char>::value>>
@@ -619,7 +635,6 @@ struct formatter<std::atomic<T>, Char,
 };
 
 #ifdef __cpp_lib_atomic_flag_test
-FMT_EXPORT
 template <typename Char>
 struct formatter<std::atomic_flag, Char> : formatter<bool, Char> {
   template <typename FormatContext>
@@ -630,36 +645,83 @@ struct formatter<std::atomic_flag, Char> : formatter<bool, Char> {
 };
 #endif  // __cpp_lib_atomic_flag_test
 
-FMT_EXPORT
-template <typename F, typename Char>
-struct formatter<std::complex<F>, Char> : nested_formatter<F, Char> {
+template <typename T, typename Char> struct formatter<std::complex<T>, Char> {
  private:
-  // Functor because C++11 doesn't support generic lambdas.
-  struct writer {
-    const formatter<std::complex<F>, Char>* f;
-    const std::complex<F>& c;
-
-    template <typename OutputIt>
-    FMT_CONSTEXPR auto operator()(OutputIt out) -> OutputIt {
-      if (c.real() != 0) {
-        auto format_full = detail::string_literal<Char, '(', '{', '}', '+', '{',
-                                                  '}', 'i', ')'>{};
-        return fmt::format_to(out, basic_string_view<Char>(format_full),
-                              f->nested(c.real()), f->nested(c.imag()));
-      }
-      auto format_imag = detail::string_literal<Char, '{', '}', 'i'>{};
-      return fmt::format_to(out, basic_string_view<Char>(format_imag),
-                            f->nested(c.imag()));
+  detail::dynamic_format_specs<Char> specs_;
+
+  template <typename FormatContext, typename OutputIt>
+  FMT_CONSTEXPR auto do_format(const std::complex<T>& c,
+                               detail::dynamic_format_specs<Char>& specs,
+                               FormatContext& ctx, OutputIt out) const
+      -> OutputIt {
+    if (c.real() != 0) {
+      *out++ = Char('(');
+      out = detail::write<Char>(out, c.real(), specs, ctx.locale());
+      specs.set_sign(sign::plus);
+      out = detail::write<Char>(out, c.imag(), specs, ctx.locale());
+      if (!detail::isfinite(c.imag())) *out++ = Char(' ');
+      *out++ = Char('i');
+      *out++ = Char(')');
+      return out;
     }
-  };
+    out = detail::write<Char>(out, c.imag(), specs, ctx.locale());
+    if (!detail::isfinite(c.imag())) *out++ = Char(' ');
+    *out++ = Char('i');
+    return out;
+  }
 
  public:
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+    if (ctx.begin() == ctx.end() || *ctx.begin() == '}') return ctx.begin();
+    return parse_format_specs(ctx.begin(), ctx.end(), specs_, ctx,
+                              detail::type_constant<T, Char>::value);
+  }
+
   template <typename FormatContext>
-  auto format(const std::complex<F>& c, FormatContext& ctx) const
+  auto format(const std::complex<T>& c, FormatContext& ctx) const
       -> decltype(ctx.out()) {
-    return this->write_padded(ctx, writer{this, c});
+    auto specs = specs_;
+    if (specs.dynamic()) {
+      detail::handle_dynamic_spec(specs.dynamic_width(), specs.width,
+                                  specs.width_ref, ctx);
+      detail::handle_dynamic_spec(specs.dynamic_precision(), specs.precision,
+                                  specs.precision_ref, ctx);
+    }
+
+    if (specs.width == 0) return do_format(c, specs, ctx, ctx.out());
+    auto buf = basic_memory_buffer<Char>();
+
+    auto outer_specs = format_specs();
+    outer_specs.width = specs.width;
+    outer_specs.copy_fill_from(specs);
+    outer_specs.set_align(specs.align());
+
+    specs.width = 0;
+    specs.set_fill({});
+    specs.set_align(align::none);
+
+    do_format(c, specs, ctx, basic_appender<Char>(buf));
+    return detail::write<Char>(ctx.out(),
+                               basic_string_view<Char>(buf.data(), buf.size()),
+                               outer_specs);
+  }
+};
+
+template <typename T, typename Char>
+struct formatter<std::reference_wrapper<T>, Char,
+                 // Guard against format_as because reference_wrapper is
+                 // implicitly convertible to T&.
+                 enable_if_t<is_formattable<remove_cvref_t<T>, Char>::value &&
+                             !detail::has_format_as<T>::value &&
+                             !detail::has_format_as_member<T>::value>>
+    : formatter<remove_cvref_t<T>, Char> {
+  template <typename FormatContext>
+  auto format(std::reference_wrapper<T> ref, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return formatter<remove_cvref_t<T>, Char>::format(ref.get(), ctx);
   }
 };
 
 FMT_END_NAMESPACE
+
 #endif  // FMT_STD_H_
diff --git a/contrib/fmt/include/fmt/xchar.h b/contrib/fmt/include/fmt/xchar.h
index b1f39ed222..9334b87fdc 100644
--- a/contrib/fmt/include/fmt/xchar.h
+++ b/contrib/fmt/include/fmt/xchar.h
@@ -10,11 +10,12 @@
 
 #include "color.h"
 #include "format.h"
+#include "ostream.h"
 #include "ranges.h"
 
 #ifndef FMT_MODULE
 #  include <cwchar>
-#  if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
+#  if FMT_USE_LOCALE
 #    include <locale>
 #  endif
 #endif
@@ -34,7 +35,8 @@ struct format_string_char<
 };
 
 template <typename S>
-struct format_string_char<S, enable_if_t<is_compile_string<S>::value>> {
+struct format_string_char<
+    S, enable_if_t<std::is_base_of<detail::compile_string, S>::value>> {
   using type = typename S::char_type;
 };
 
@@ -43,7 +45,7 @@ using format_string_char_t = typename format_string_char<S>::type;
 
 inline auto write_loc(basic_appender<wchar_t> out, loc_value value,
                       const format_specs& specs, locale_ref loc) -> bool {
-#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+#if FMT_USE_LOCALE
   auto& numpunct =
       std::use_facet<std::numpunct<wchar_t>>(loc.get<std::locale>());
   auto separator = std::wstring();
@@ -53,36 +55,72 @@ inline auto write_loc(basic_appender<wchar_t> out, loc_value value,
 #endif
   return false;
 }
+
+template <typename Char>
+void vformat_to(buffer<Char>& buf, basic_string_view<Char> fmt,
+                basic_format_args<buffered_context<Char>> args,
+                locale_ref loc = {}) {
+  static_assert(!std::is_same<Char, char>::value, "");
+  auto out = basic_appender<Char>(buf);
+  parse_format_string(
+      fmt, format_handler<Char>{parse_context<Char>(fmt), {out, args, loc}});
+}
 }  // namespace detail
 
 FMT_BEGIN_EXPORT
 
 using wstring_view = basic_string_view<wchar_t>;
-using wformat_parse_context = basic_format_parse_context<wchar_t>;
+using wformat_parse_context = parse_context<wchar_t>;
 using wformat_context = buffered_context<wchar_t>;
 using wformat_args = basic_format_args<wformat_context>;
 using wmemory_buffer = basic_memory_buffer<wchar_t>;
 
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
-// Workaround broken conversion on older gcc.
-template <typename... Args> using wformat_string = wstring_view;
-inline auto runtime(wstring_view s) -> wstring_view { return s; }
-#else
-template <typename... Args>
-using wformat_string = basic_format_string<wchar_t, type_identity_t<Args>...>;
+template <typename Char, typename... T> struct basic_fstring {
+ private:
+  basic_string_view<Char> str_;
+
+  static constexpr int num_static_named_args =
+      detail::count_static_named_args<T...>();
+
+  using checker = detail::format_string_checker<
+      Char, static_cast<int>(sizeof...(T)), num_static_named_args,
+      num_static_named_args != detail::count_named_args<T...>()>;
+
+  using arg_pack = detail::arg_pack<T...>;
+
+ public:
+  using t = basic_fstring;
+
+  template <typename S,
+            FMT_ENABLE_IF(
+                std::is_convertible<const S&, basic_string_view<Char>>::value)>
+  FMT_CONSTEVAL FMT_ALWAYS_INLINE basic_fstring(const S& s) : str_(s) {
+    if (FMT_USE_CONSTEVAL)
+      detail::parse_format_string<Char>(s, checker(s, arg_pack()));
+  }
+  template <typename S,
+            FMT_ENABLE_IF(std::is_base_of<detail::compile_string, S>::value&&
+                              std::is_same<typename S::char_type, Char>::value)>
+  FMT_ALWAYS_INLINE basic_fstring(const S&) : str_(S()) {
+    FMT_CONSTEXPR auto sv = basic_string_view<Char>(S());
+    FMT_CONSTEXPR int ignore =
+        (parse_format_string(sv, checker(sv, arg_pack())), 0);
+    detail::ignore_unused(ignore);
+  }
+  basic_fstring(runtime_format_string<Char> fmt) : str_(fmt.str) {}
+
+  operator basic_string_view<Char>() const { return str_; }
+  auto get() const -> basic_string_view<Char> { return str_; }
+};
+
+template <typename Char, typename... T>
+using basic_format_string = basic_fstring<Char, T...>;
+
+template <typename... T>
+using wformat_string = typename basic_format_string<wchar_t, T...>::t;
 inline auto runtime(wstring_view s) -> runtime_format_string<wchar_t> {
   return {{s}};
 }
-#endif
-
-template <> struct is_char<wchar_t> : std::true_type {};
-template <> struct is_char<char16_t> : std::true_type {};
-template <> struct is_char<char32_t> : std::true_type {};
-
-#ifdef __cpp_char8_t
-template <>
-struct is_char<char8_t> : bool_constant<detail::is_utf8_enabled()> {};
-#endif
 
 template <typename... T>
 constexpr auto make_wformat_args(T&... args)
@@ -90,14 +128,13 @@ constexpr auto make_wformat_args(T&... args)
   return fmt::make_format_args<wformat_context>(args...);
 }
 
+#if !FMT_USE_NONTYPE_TEMPLATE_ARGS
 inline namespace literals {
-#if FMT_USE_USER_DEFINED_LITERALS && !FMT_USE_NONTYPE_TEMPLATE_ARGS
-constexpr auto operator""_a(const wchar_t* s, size_t)
-    -> detail::udl_arg<wchar_t> {
+inline auto operator""_a(const wchar_t* s, size_t) -> detail::udl_arg<wchar_t> {
   return {s};
 }
-#endif
 }  // namespace literals
+#endif
 
 template <typename It, typename Sentinel>
 auto join(It begin, Sentinel end, wstring_view sep)
@@ -105,9 +142,9 @@ auto join(It begin, Sentinel end, wstring_view sep)
   return {begin, end, sep};
 }
 
-template <typename Range>
+template <typename Range, FMT_ENABLE_IF(!is_tuple_like<Range>::value)>
 auto join(Range&& range, wstring_view sep)
-    -> join_view<detail::iterator_t<Range>, detail::sentinel_t<Range>,
+    -> join_view<decltype(std::begin(range)), decltype(std::end(range)),
                  wchar_t> {
   return join(std::begin(range), std::end(range), sep);
 }
@@ -118,19 +155,19 @@ auto join(std::initializer_list<T> list, wstring_view sep)
   return join(std::begin(list), std::end(list), sep);
 }
 
-template <typename... T>
-auto join(const std::tuple<T...>& tuple, basic_string_view<wchar_t> sep)
-    -> tuple_join_view<wchar_t, T...> {
+template <typename Tuple, FMT_ENABLE_IF(is_tuple_like<Tuple>::value)>
+auto join(const Tuple& tuple, basic_string_view<wchar_t> sep)
+    -> tuple_join_view<Tuple, wchar_t> {
   return {tuple, sep};
 }
 
 template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
-auto vformat(basic_string_view<Char> format_str,
-             typename detail::vformat_args<Char>::type args)
+auto vformat(basic_string_view<Char> fmt,
+             basic_format_args<buffered_context<Char>> args)
     -> std::basic_string<Char> {
   auto buf = basic_memory_buffer<Char>();
-  detail::vformat_to(buf, format_str, args);
-  return to_string(buf);
+  detail::vformat_to(buf, fmt, args);
+  return {buf.data(), buf.size()};
 }
 
 template <typename... T>
@@ -151,40 +188,38 @@ template <typename S, typename... T,
           typename Char = detail::format_string_char_t<S>,
           FMT_ENABLE_IF(!std::is_same<Char, char>::value &&
                         !std::is_same<Char, wchar_t>::value)>
-auto format(const S& format_str, T&&... args) -> std::basic_string<Char> {
-  return vformat(detail::to_string_view(format_str),
+auto format(const S& fmt, T&&... args) -> std::basic_string<Char> {
+  return vformat(detail::to_string_view(fmt),
                  fmt::make_format_args<buffered_context<Char>>(args...));
 }
 
-template <typename Locale, typename S,
-          typename Char = detail::format_string_char_t<S>,
-          FMT_ENABLE_IF(detail::is_locale<Locale>::value&&
-                            detail::is_exotic_char<Char>::value)>
-inline auto vformat(const Locale& loc, const S& format_str,
-                    typename detail::vformat_args<Char>::type args)
+template <typename S, typename Char = detail::format_string_char_t<S>,
+          FMT_ENABLE_IF(detail::is_exotic_char<Char>::value)>
+inline auto vformat(locale_ref loc, const S& fmt,
+                    basic_format_args<buffered_context<Char>> args)
     -> std::basic_string<Char> {
-  return detail::vformat(loc, detail::to_string_view(format_str), args);
+  auto buf = basic_memory_buffer<Char>();
+  detail::vformat_to(buf, detail::to_string_view(fmt), args, loc);
+  return {buf.data(), buf.size()};
 }
 
-template <typename Locale, typename S, typename... T,
+template <typename S, typename... T,
           typename Char = detail::format_string_char_t<S>,
-          FMT_ENABLE_IF(detail::is_locale<Locale>::value&&
-                            detail::is_exotic_char<Char>::value)>
-inline auto format(const Locale& loc, const S& format_str, T&&... args)
+          FMT_ENABLE_IF(detail::is_exotic_char<Char>::value)>
+inline auto format(locale_ref loc, const S& fmt, T&&... args)
     -> std::basic_string<Char> {
-  return detail::vformat(
-      loc, detail::to_string_view(format_str),
-      fmt::make_format_args<buffered_context<Char>>(args...));
+  return vformat(loc, detail::to_string_view(fmt),
+                 fmt::make_format_args<buffered_context<Char>>(args...));
 }
 
 template <typename OutputIt, typename S,
           typename Char = detail::format_string_char_t<S>,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
                             detail::is_exotic_char<Char>::value)>
-auto vformat_to(OutputIt out, const S& format_str,
-                typename detail::vformat_args<Char>::type args) -> OutputIt {
+auto vformat_to(OutputIt out, const S& fmt,
+                basic_format_args<buffered_context<Char>> args) -> OutputIt {
   auto&& buf = detail::get_buffer<Char>(out);
-  detail::vformat_to(buf, detail::to_string_view(format_str), args);
+  detail::vformat_to(buf, detail::to_string_view(fmt), args);
   return detail::get_iterator(buf, out);
 }
 
@@ -198,42 +233,37 @@ inline auto format_to(OutputIt out, const S& fmt, T&&... args) -> OutputIt {
                     fmt::make_format_args<buffered_context<Char>>(args...));
 }
 
-template <typename Locale, typename S, typename OutputIt, typename... Args,
+template <typename S, typename OutputIt, typename... Args,
           typename Char = detail::format_string_char_t<S>,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
-                            detail::is_locale<Locale>::value&&
-                                detail::is_exotic_char<Char>::value)>
-inline auto vformat_to(OutputIt out, const Locale& loc, const S& format_str,
-                       typename detail::vformat_args<Char>::type args)
+                            detail::is_exotic_char<Char>::value)>
+inline auto vformat_to(OutputIt out, locale_ref loc, const S& fmt,
+                       basic_format_args<buffered_context<Char>> args)
     -> OutputIt {
   auto&& buf = detail::get_buffer<Char>(out);
-  vformat_to(buf, detail::to_string_view(format_str), args,
-             detail::locale_ref(loc));
+  vformat_to(buf, detail::to_string_view(fmt), args, loc);
   return detail::get_iterator(buf, out);
 }
 
-template <typename OutputIt, typename Locale, typename S, typename... T,
+template <typename OutputIt, typename S, typename... T,
           typename Char = detail::format_string_char_t<S>,
           bool enable = detail::is_output_iterator<OutputIt, Char>::value &&
-                        detail::is_locale<Locale>::value &&
                         detail::is_exotic_char<Char>::value>
-inline auto format_to(OutputIt out, const Locale& loc, const S& format_str,
-                      T&&... args) ->
-    typename std::enable_if<enable, OutputIt>::type {
-  return vformat_to(out, loc, detail::to_string_view(format_str),
+inline auto format_to(OutputIt out, locale_ref loc, const S& fmt, T&&... args)
+    -> typename std::enable_if<enable, OutputIt>::type {
+  return vformat_to(out, loc, detail::to_string_view(fmt),
                     fmt::make_format_args<buffered_context<Char>>(args...));
 }
 
 template <typename OutputIt, typename Char, typename... Args,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
                             detail::is_exotic_char<Char>::value)>
-inline auto vformat_to_n(OutputIt out, size_t n,
-                         basic_string_view<Char> format_str,
-                         typename detail::vformat_args<Char>::type args)
+inline auto vformat_to_n(OutputIt out, size_t n, basic_string_view<Char> fmt,
+                         basic_format_args<buffered_context<Char>> args)
     -> format_to_n_result<OutputIt> {
   using traits = detail::fixed_buffer_traits;
   auto buf = detail::iterator_buffer<OutputIt, Char, traits>(out, n);
-  detail::vformat_to(buf, format_str, args);
+  detail::vformat_to(buf, fmt, args);
   return {buf.out(), buf.count()};
 }
 
@@ -287,29 +317,33 @@ template <typename... T> void println(wformat_string<T...> fmt, T&&... args) {
   return print(L"{}\n", fmt::format(fmt, std::forward<T>(args)...));
 }
 
-inline auto vformat(const text_style& ts, wstring_view fmt, wformat_args args)
+inline auto vformat(text_style ts, wstring_view fmt, wformat_args args)
     -> std::wstring {
   auto buf = wmemory_buffer();
   detail::vformat_to(buf, ts, fmt, args);
-  return fmt::to_string(buf);
+  return {buf.data(), buf.size()};
 }
 
 template <typename... T>
-inline auto format(const text_style& ts, wformat_string<T...> fmt, T&&... args)
+inline auto format(text_style ts, wformat_string<T...> fmt, T&&... args)
     -> std::wstring {
   return fmt::vformat(ts, fmt, fmt::make_wformat_args(args...));
 }
 
+inline void vprint(std::wostream& os, wstring_view fmt, wformat_args args) {
+  auto buffer = basic_memory_buffer<wchar_t>();
+  detail::vformat_to(buffer, fmt, args);
+  detail::write_buffer(os, buffer);
+}
+
 template <typename... T>
-FMT_DEPRECATED void print(std::FILE* f, const text_style& ts,
-                          wformat_string<T...> fmt, const T&... args) {
-  vprint(f, ts, fmt, fmt::make_wformat_args(args...));
+void print(std::wostream& os, wformat_string<T...> fmt, T&&... args) {
+  vprint(os, fmt, fmt::make_format_args<buffered_context<wchar_t>>(args...));
 }
 
 template <typename... T>
-FMT_DEPRECATED void print(const text_style& ts, wformat_string<T...> fmt,
-                          const T&... args) {
-  return print(stdout, ts, fmt, args...);
+void println(std::wostream& os, wformat_string<T...> fmt, T&&... args) {
+  print(os, L"{}\n", fmt::format(fmt, std::forward<T>(args)...));
 }
 
 /// Converts `value` to `std::wstring` using the default format for type `T`.