]> git.ipfire.org Git - thirdparty/gcc.git/commitdiff
PR libstdc++/71044 optimize std::filesystem::path construction
authorJonathan Wakely <jwakely@redhat.com>
Thu, 13 Dec 2018 20:33:55 +0000 (20:33 +0000)
committerJonathan Wakely <redi@gcc.gnu.org>
Thu, 13 Dec 2018 20:33:55 +0000 (20:33 +0000)
This new implementation has a smaller footprint than the previous
implementation, due to replacing std::vector<_Cmpt> with a custom pimpl
type that only needs a single pointer. The _M_type enumeration is also
combined with the pimpl type, by using a tagged pointer, reducing
sizeof(path) further still.

Construction and modification of paths is now done more efficiently, by
splitting the input into a stack-based buffer of string_view objects
instead of a dynamically-allocated vector containing strings. Once the
final size is known only a single allocation is needed to reserve space
for it.  The append and concat operations no longer require constructing
temporary path objects, nor re-parsing the entire native pathname.

This results in algorithmic improvements to path construction, and
working with large paths is much faster.

PR libstdc++/71044
* include/bits/fs_path.h (path::path(path&&)): Add noexcept when
appropriate. Move _M_cmpts instead of reparsing the native pathname.
(path::operator=(const path&)): Do not define as defaulted.
(path::operator/=, path::append): Call _M_append.
(path::concat): Call _M_concat.
(path::path(string_type, _Type): Change type of first parameter to
basic_string_view<value_type>.
(path::_M_append(basic_string_view<value_type>)): New member function.
(path::_M_concat(basic_string_view<value_type>)): New member function.
(_S_convert(value_type*, __null_terminated)): Return string view.
(_S_convert(const value_type*, __null_terminated)): Return string view.
(_S_convert(value_type*, value_type*))
(_S_convert(const value_type*, const value_type*)): Add overloads for
pairs of pointers.
(_S_convert(_InputIterator, __null_terminated)): Construct string_type
explicitly, for cases where _S_convert returns a string view.
(path::_S_is_dir_sep): Replace with non-member is_dir_sep.
(path::_M_trim, path::_M_add_root_name, path::_M_add_root_dir)
(path::_M_add_filename): Remove.
(path::_M_type()): New member function to replace _M_type data member.
(path::_List): Define new struct type instead of using std::vector.
(path::_Cmpt::_Cmpt(string_type, _Type, size_t)): Change type of
first parameter to basic_string_view<value_type>.
(path::operator+=(const path&)): Do not define inline.
(path::operator+=(const string_type&)): Call _M_concat.
(path::operator+=(const value_type*)): Likewise.
(path::operator+=(value_type)): Likewise.
(path::operator+=(basic_string_view<value_type>)): Likewise.
(path::operator/=(const path&)): Do not define inline.
(path::_M_append(path)): Remove.
* python/libstdcxx/v6/printers.py (StdPathPrinter): New printer that
understands the new path::_List type.
* src/filesystem/std-path.cc (is_dir_sep): New function to replace
path::_S_is_dir_sep.
(path::_Parser): New helper class to parse strings as paths.
(path::_List::_Impl): Define container type for path components.
(path::_List): Define members.
(path::operator=(const path&)): Define explicitly, to provide the
strong exception safety guarantee.
(path::operator/=(const path&)): Implement manually by processing
each component of the argument, rather than using _M_split_cmpts
to parse the entire string again.
(path::_M_append(string_type)): Likewise.
(path::operator+=(const path&)): Likewise.
(path::_M_concat(string_type)): Likewise.
(path::remove_filename()): Perform trim directly instead of calling
_M_trim().
(path::_M_split_cmpts()): Rewrite in terms of _Parser class.
(path::_M_trim, path::_M_add_root_name, path::_M_add_root_dir)
(path::_M_add_filename): Remove.
* testsuite/27_io/filesystem/path/append/source.cc: Test appending a
string view that aliases the path.
testsuite/27_io/filesystem/path/concat/strings.cc: Test concatenating
a string view that aliases the path.

From-SVN: r267106

libstdc++-v3/ChangeLog
libstdc++-v3/include/bits/fs_path.h
libstdc++-v3/python/libstdcxx/v6/printers.py
libstdc++-v3/src/filesystem/std-path.cc
libstdc++-v3/testsuite/27_io/filesystem/path/append/source.cc
libstdc++-v3/testsuite/27_io/filesystem/path/concat/strings.cc

index cde8426089ab5d2ada82c99bad9a3ed25a3f12d7..c1a25028f250cc0b7773a3ecc208913c2a00c2bb 100644 (file)
@@ -1,5 +1,61 @@
 2018-12-13  Jonathan Wakely  <jwakely@redhat.com>
 
+       PR libstdc++/71044
+       * include/bits/fs_path.h (path::path(path&&)): Add noexcept when
+       appropriate. Move _M_cmpts instead of reparsing the native pathname.
+       (path::operator=(const path&)): Do not define as defaulted.
+       (path::operator/=, path::append): Call _M_append.
+       (path::concat): Call _M_concat.
+       (path::path(string_type, _Type): Change type of first parameter to
+       basic_string_view<value_type>.
+       (path::_M_append(basic_string_view<value_type>)): New member function.
+       (path::_M_concat(basic_string_view<value_type>)): New member function.
+       (_S_convert(value_type*, __null_terminated)): Return string view.
+       (_S_convert(const value_type*, __null_terminated)): Return string view.
+       (_S_convert(value_type*, value_type*))
+       (_S_convert(const value_type*, const value_type*)): Add overloads for
+       pairs of pointers.
+       (_S_convert(_InputIterator, __null_terminated)): Construct string_type
+       explicitly, for cases where _S_convert returns a string view.
+       (path::_S_is_dir_sep): Replace with non-member is_dir_sep.
+       (path::_M_trim, path::_M_add_root_name, path::_M_add_root_dir)
+       (path::_M_add_filename): Remove.
+       (path::_M_type()): New member function to replace _M_type data member.
+       (path::_List): Define new struct type instead of using std::vector.
+       (path::_Cmpt::_Cmpt(string_type, _Type, size_t)): Change type of
+       first parameter to basic_string_view<value_type>.
+       (path::operator+=(const path&)): Do not define inline.
+       (path::operator+=(const string_type&)): Call _M_concat.
+       (path::operator+=(const value_type*)): Likewise.
+       (path::operator+=(value_type)): Likewise.
+       (path::operator+=(basic_string_view<value_type>)): Likewise.
+       (path::operator/=(const path&)): Do not define inline.
+       (path::_M_append(path)): Remove.
+       * python/libstdcxx/v6/printers.py (StdPathPrinter): New printer that
+       understands the new path::_List type.
+       * src/filesystem/std-path.cc (is_dir_sep): New function to replace
+       path::_S_is_dir_sep.
+       (path::_Parser): New helper class to parse strings as paths.
+       (path::_List::_Impl): Define container type for path components.
+       (path::_List): Define members.
+       (path::operator=(const path&)): Define explicitly, to provide the
+       strong exception safety guarantee.
+       (path::operator/=(const path&)): Implement manually by processing
+       each component of the argument, rather than using _M_split_cmpts
+       to parse the entire string again.
+       (path::_M_append(string_type)): Likewise.
+       (path::operator+=(const path&)): Likewise.
+       (path::_M_concat(string_type)): Likewise.
+       (path::remove_filename()): Perform trim directly instead of calling
+       _M_trim().
+       (path::_M_split_cmpts()): Rewrite in terms of _Parser class.
+       (path::_M_trim, path::_M_add_root_name, path::_M_add_root_dir)
+       (path::_M_add_filename): Remove.
+       * testsuite/27_io/filesystem/path/append/source.cc: Test appending a
+       string view that aliases the path.
+       testsuite/27_io/filesystem/path/concat/strings.cc: Test concatenating
+       a string view that aliases the path.
+
        * testsuite/27_io/filesystem/path/generation/proximate.cc: Use
        preferred directory separators for normalized paths.
        * testsuite/27_io/filesystem/path/generation/relative.cc: Likewise.
index 075b3ab5ef82b43293eada2bf0131c0c284904e8..c69001bcc3c09c9bf8e7af37f49f1fd81705fb41 100644 (file)
@@ -34,7 +34,6 @@
 
 #include <utility>
 #include <type_traits>
-#include <vector>
 #include <locale>
 #include <iosfwd>
 #include <iomanip>
@@ -45,6 +44,7 @@
 #include <bits/locale_conv.h>
 #include <ext/concurrence.h>
 #include <bits/shared_ptr.h>
+#include <bits/unique_ptr.h>
 
 #if defined(_WIN32) && !defined(__CYGWIN__)
 # define _GLIBCXX_FILESYSTEM_IS_WINDOWS 1
@@ -169,12 +169,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
     path(const path& __p) = default;
 
-    path(path&& __p) noexcept
-    : _M_pathname(std::move(__p._M_pathname)), _M_type(__p._M_type)
-    {
-      _M_split_cmpts();
-      __p.clear();
-    }
+    path(path&& __p)
+#if _GLIBCXX_USE_CXX11_ABI || _GLIBCXX_FULLY_DYNAMIC_STRING == 0
+      noexcept
+#endif
+    : _M_pathname(std::move(__p._M_pathname)),
+      _M_cmpts(std::move(__p._M_cmpts))
+    { __p.clear(); }
 
     path(string_type&& __source, format = auto_format)
     : _M_pathname(std::move(__source))
@@ -213,8 +214,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
     // assignments
 
-    path& operator=(const path& __p) = default;
-    path& operator=(path&& __p) noexcept;
+    path& operator=(const path&);
+    path& operator=(path&&) noexcept;
     path& operator=(string_type&& __source);
     path& assign(string_type&& __source);
 
@@ -240,17 +241,26 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
     template <class _Source>
       _Path<_Source>&
       operator/=(_Source const& __source)
-      { return _M_append(path(__source)); }
+      {
+       _M_append(_S_convert(_S_range_begin(__source), _S_range_end(__source)));
+       return *this;
+      }
 
     template<typename _Source>
       _Path<_Source>&
       append(_Source const& __source)
-      { return _M_append(path(__source)); }
+      {
+       _M_append(_S_convert(_S_range_begin(__source), _S_range_end(__source)));
+       return *this;
+      }
 
     template<typename _InputIterator>
       _Path<_InputIterator, _InputIterator>&
       append(_InputIterator __first, _InputIterator __last)
-      { return _M_append(path(__first, __last)); }
+      {
+       _M_append(_S_convert(__first, __last));
+       return *this;
+      }
 
     // concatenation
 
@@ -271,12 +281,18 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
     template<typename _Source>
       _Path<_Source>&
       concat(_Source const& __x)
-      { return *this += _S_convert(_S_range_begin(__x), _S_range_end(__x)); }
+      {
+       _M_concat(_S_convert(_S_range_begin(__x), _S_range_end(__x)));
+       return *this;
+      }
 
     template<typename _InputIterator>
       _Path<_InputIterator, _InputIterator>&
       concat(_InputIterator __first, _InputIterator __last)
-      { return *this += _S_convert(__first, __last); }
+      {
+       _M_concat(_S_convert(__first, __last));
+       return *this;
+      }
 
     // modifiers
 
@@ -402,30 +418,41 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
   private:
     enum class _Type : unsigned char {
-       _Multi, _Root_name, _Root_dir, _Filename
+      _Multi = 0, _Root_name, _Root_dir, _Filename
     };
 
-    path(string_type __str, _Type __type) : _M_pathname(__str), _M_type(__type)
+    path(basic_string_view<value_type> __str, _Type __type)
+    : _M_pathname(__str)
     {
-      __glibcxx_assert(_M_type != _Type::_Multi);
+      __glibcxx_assert(__type != _Type::_Multi);
+      _M_cmpts.type(__type);
     }
 
     enum class _Split { _Stem, _Extension };
 
-    path& _M_append(path __p);
+    void _M_append(basic_string_view<value_type>);
+    void _M_concat(basic_string_view<value_type>);
 
     pair<const string_type*, size_t> _M_find_extension() const;
 
     template<typename _CharT>
       struct _Cvt;
 
-    static string_type
+    static basic_string_view<value_type>
     _S_convert(value_type* __src, __null_terminated)
-    { return string_type(__src); }
+    { return __src; }
 
-    static string_type
+    static basic_string_view<value_type>
     _S_convert(const value_type* __src, __null_terminated)
-    { return string_type(__src); }
+    { return __src; }
+
+    static basic_string_view<value_type>
+    _S_convert(value_type* __first, value_type* __last)
+    { return {__first, __last - __first}; }
+
+    static basic_string_view<value_type>
+    _S_convert(const value_type* __first, const value_type* __last)
+    { return {__first, __last - __first}; }
 
     template<typename _Iter>
       static string_type
@@ -440,8 +467,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       static string_type
       _S_convert(_InputIterator __src, __null_terminated)
       {
+       // Read from iterator into basic_string until a null value is seen:
        auto __s = _S_string_from_iter(__src);
-       return _S_convert(__s.c_str(), __s.c_str() + __s.size());
+       // Convert (if needed) from iterator's value type to path::value_type:
+       return string_type(_S_convert(__s.data(), __s.data() + __s.size()));
       }
 
     static string_type
@@ -469,27 +498,65 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       static basic_string<_CharT, _Traits, _Allocator>
       _S_str_convert(const string_type&, const _Allocator& __a);
 
-    bool _S_is_dir_sep(value_type __ch)
-    {
-#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
-      return __ch == L'/' || __ch == preferred_separator;
-#else
-      return __ch == '/';
-#endif
-    }
-
     void _M_split_cmpts();
-    void _M_trim();
-    void _M_add_root_name(size_t __n);
-    void _M_add_root_dir(size_t __pos);
-    void _M_add_filename(size_t __pos, size_t __n);
+
+    _Type _M_type() const noexcept { return _M_cmpts.type(); }
 
     string_type _M_pathname;
 
     struct _Cmpt;
-    using _List = _GLIBCXX_STD_C::vector<_Cmpt>;
-    _List _M_cmpts; // empty unless _M_type == _Type::_Multi
-    _Type _M_type = _Type::_Filename;
+
+    struct _List
+    {
+      using value_type = _Cmpt;
+      using iterator = value_type*;
+      using const_iterator = const value_type*;
+
+      _List();
+      _List(const _List&);
+      _List(_List&&) = default;
+      _List& operator=(const _List&);
+      _List& operator=(_List&&) = default;
+      ~_List() = default;
+
+      _Type type() const noexcept
+      { return _Type{reinterpret_cast<uintptr_t>(_M_impl.get()) & 0x3}; }
+
+      void type(_Type) noexcept;
+
+      int size() const noexcept; // zero unless type() == _Type::_Multi
+      bool empty() const noexcept; // true unless type() == _Type::_Multi
+      void clear();
+      void swap(_List& __l) noexcept { _M_impl.swap(__l._M_impl); }
+      int capacity() const noexcept;
+      void reserve(int, bool); ///< @pre type() == _Type::_Multi
+
+      // All the member functions below here have a precondition !empty()
+      // (and they should only be called from within the library).
+
+      iterator begin();
+      iterator end();
+      const_iterator begin() const;
+      const_iterator end() const;
+
+      value_type& front() noexcept;
+      value_type& back() noexcept;
+      const value_type& front() const noexcept;
+      const value_type& back() const noexcept;
+
+      void erase(const_iterator);
+      void erase(const_iterator, const_iterator);
+
+      struct _Impl;
+      struct _Impl_deleter
+      {
+       void operator()(_Impl*) const noexcept;
+      };
+      unique_ptr<_Impl, _Impl_deleter> _M_impl;
+    };
+    _List _M_cmpts;
+
+    struct _Parser;
   };
 
   inline void swap(path& __lhs, path& __rhs) noexcept { __lhs.swap(__rhs); }
@@ -605,8 +672,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
   struct path::_Cmpt : path
   {
-    _Cmpt(string_type __s, _Type __t, size_t __pos)
-      : path(std::move(__s), __t), _M_pos(__pos) { }
+    _Cmpt(basic_string_view<value_type> __s, _Type __t, size_t __pos)
+      : path(__s, __t), _M_pos(__pos) { }
 
     _Cmpt() : _M_pos(-1) { }
 
@@ -733,7 +800,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   private:
     friend class path;
 
-    bool _M_is_multi() const { return _M_path->_M_type == _Type::_Multi; }
+    bool _M_is_multi() const { return _M_path->_M_type() == _Type::_Multi; }
 
     friend difference_type
     __path_iter_distance(const iterator& __first, const iterator& __last)
@@ -785,7 +852,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   {
     _M_pathname = std::move(__p._M_pathname);
     _M_cmpts = std::move(__p._M_cmpts);
-    _M_type = __p._M_type;
     __p.clear();
     return *this;
   }
@@ -798,41 +864,31 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   path::assign(string_type&& __source)
   { return *this = path(std::move(__source)); }
 
-  inline path&
-  path::operator+=(const path& __p)
-  {
-    return operator+=(__p.native());
-  }
-
   inline path&
   path::operator+=(const string_type& __x)
   {
-    _M_pathname += __x;
-    _M_split_cmpts();
+    _M_concat(__x);
     return *this;
   }
 
   inline path&
   path::operator+=(const value_type* __x)
   {
-    _M_pathname += __x;
-    _M_split_cmpts();
+    _M_concat(__x);
     return *this;
   }
 
   inline path&
   path::operator+=(value_type __x)
   {
-    _M_pathname += __x;
-    _M_split_cmpts();
+    _M_concat(basic_string_view<value_type>(&__x, 1));
     return *this;
   }
 
   inline path&
   path::operator+=(basic_string_view<value_type> __x)
   {
-    _M_pathname.append(__x.data(), __x.size());
-    _M_split_cmpts();
+    _M_concat(__x);
     return *this;
   }
 
@@ -858,7 +914,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   {
     _M_pathname.swap(__rhs._M_pathname);
     _M_cmpts.swap(__rhs._M_cmpts);
-    std::swap(_M_type, __rhs._M_type);
   }
 
   template<typename _CharT, typename _Traits, typename _Allocator>
@@ -968,7 +1023,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 #endif
       string_type __str(__a);
 
-      if (_M_type == _Type::_Root_dir)
+      if (_M_type() == _Type::_Root_dir)
        __str.assign(1, __slash);
       else
        {
@@ -979,7 +1034,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
              if (__add_slash)
                __str += __slash;
              __str += __elem._M_pathname;
-             __add_slash = __elem._M_type == _Type::_Filename;
+             __add_slash = __elem._M_type() == _Type::_Filename;
            }
        }
 
@@ -1026,14 +1081,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   {
     if (empty())
       return {};
-    else if (_M_type == _Type::_Filename)
+    else if (_M_type() == _Type::_Filename)
       return *this;
-    else if (_M_type == _Type::_Multi)
+    else if (_M_type() == _Type::_Multi)
       {
        if (_M_pathname.back() == preferred_separator)
          return {};
        auto& __last = *--end();
-       if (__last._M_type == _Type::_Filename)
+       if (__last._M_type() == _Type::_Filename)
          return __last;
       }
     return {};
@@ -1084,7 +1139,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   inline path::iterator
   path::begin() const
   {
-    if (_M_type == _Type::_Multi)
+    if (_M_type() == _Type::_Multi)
       return iterator(this, _M_cmpts.begin());
     return iterator(this, empty());
   }
@@ -1092,48 +1147,16 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   inline path::iterator
   path::end() const
   {
-    if (_M_type == _Type::_Multi)
+    if (_M_type() == _Type::_Multi)
       return iterator(this, _M_cmpts.end());
     return iterator(this, true);
   }
 
-#ifndef _GLIBCXX_FILESYSTEM_IS_WINDOWS
-  inline path& path::operator/=(const path& __p)
-  {
-    // Much simpler than the specification in the standard,
-    // as any path with root-name or root-dir is absolute.
-    if (__p.is_absolute())
-      operator=(__p);
-    else
-      {
-       if (has_filename() || (_M_type == _Type::_Root_name))
-         _M_pathname += preferred_separator;
-       _M_pathname += __p.native();
-       _M_split_cmpts();
-      }
-    return *this;
-  }
-#endif
-
-  inline path&
-  path::_M_append(path __p)
-  {
-    if (__p.is_absolute())
-      operator=(std::move(__p));
-#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
-    else if (__p.has_root_name() && __p.root_name() != root_name())
-      operator=(std::move(__p));
-#endif
-    else
-      operator/=(const_cast<const path&>(__p));
-    return *this;
-  }
-
   inline path::iterator&
   path::iterator::operator++()
   {
     __glibcxx_assert(_M_path != nullptr);
-    if (_M_path->_M_type == _Type::_Multi)
+    if (_M_path->_M_type() == _Type::_Multi)
       {
        __glibcxx_assert(_M_cur != _M_path->_M_cmpts.end());
        ++_M_cur;
@@ -1150,7 +1173,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   path::iterator::operator--()
   {
     __glibcxx_assert(_M_path != nullptr);
-    if (_M_path->_M_type == _Type::_Multi)
+    if (_M_path->_M_type() == _Type::_Multi)
       {
        __glibcxx_assert(_M_cur != _M_path->_M_cmpts.begin());
        --_M_cur;
@@ -1167,7 +1190,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   path::iterator::operator*() const
   {
     __glibcxx_assert(_M_path != nullptr);
-    if (_M_path->_M_type == _Type::_Multi)
+    if (_M_path->_M_type() == _Type::_Multi)
       {
        __glibcxx_assert(_M_cur != _M_path->_M_cmpts.end());
        return *_M_cur;
@@ -1182,7 +1205,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       return false;
     if (_M_path == nullptr)
       return true;
-    if (_M_path->_M_type == path::_Type::_Multi)
+    if (_M_path->_M_type() == path::_Type::_Multi)
       return _M_cur == __rhs._M_cur;
     return _M_at_end == __rhs._M_at_end;
   }
index 7c3c9d00ef309d32a26d44c297f92a6841f681fa..2baaf1e8b731002fa961b76fa91888d7262e1ba2 100644 (file)
@@ -1244,6 +1244,77 @@ class StdExpPathPrinter:
     def children(self):
         return self._iterator(self.val['_M_cmpts'])
 
+class StdPathPrinter:
+    "Print a std::filesystem::path"
+
+    def __init__ (self, typename, val):
+        self.val = val
+        self.typename = typename
+        impl = self.val['_M_cmpts']['_M_impl']['_M_t']['_M_t']['_M_head_impl']
+        self.type = impl.cast(gdb.lookup_type('uintptr_t')) & 3
+        if self.type == 0:
+            self.impl = impl
+        else:
+            self.impl = None
+
+    def _path_type(self):
+        t = str(self.type.cast(gdb.lookup_type(self.typename + '::_Type')))
+        if t[-9:] == '_Root_dir':
+            return "root-directory"
+        if t[-10:] == '_Root_name':
+            return "root-name"
+        return None
+
+    def to_string (self):
+        path = "%s" % self.val ['_M_pathname']
+        if self.type != 0:
+            t = self._path_type()
+            if t:
+                path = '%s [%s]' % (path, t)
+        return "filesystem::path %s" % path
+
+    class _iterator(Iterator):
+        def __init__(self, impl, pathtype):
+            if impl:
+                # We can't access _Impl::_M_size because _Impl is incomplete
+                # so cast to int* to access the _M_size member at offset zero,
+                int_type = gdb.lookup_type('int')
+                cmpt_type = gdb.lookup_type(pathtype+'::_Cmpt')
+                char_type = gdb.lookup_type('char')
+                impl = impl.cast(int_type.pointer())
+                size = impl.dereference()
+                #self.capacity = (impl + 1).dereference()
+                if hasattr(gdb.Type, 'alignof'):
+                    sizeof_Impl = max(2 * int_type.sizeof, cmpt_type.alignof)
+                else:
+                    sizeof_Impl = 2 * int_type.sizeof
+                begin = impl.cast(char_type.pointer()) + sizeof_Impl
+                self.item = begin.cast(cmpt_type.pointer())
+                self.finish = self.item + size
+                self.count = 0
+            else:
+                self.item = None
+                self.finish = None
+
+        def __iter__(self):
+            return self
+
+        def __next__(self):
+            if self.item == self.finish:
+                raise StopIteration
+            item = self.item.dereference()
+            count = self.count
+            self.count = self.count + 1
+            self.item = self.item + 1
+            path = item['_M_pathname']
+            t = StdPathPrinter(item.type.name, item)._path_type()
+            if not t:
+                t = count
+            return ('[%s]' % t, path)
+
+    def children(self):
+        return self._iterator(self.impl, self.typename)
+
 
 class StdPairPrinter:
     "Print a std::pair object, with 'first' and 'second' as children"
@@ -1759,9 +1830,9 @@ def build_libstdcxx_dictionary ():
     libstdcxx_printer.add_version('std::experimental::filesystem::v1::__cxx11::',
                                   'path', StdExpPathPrinter)
     libstdcxx_printer.add_version('std::filesystem::',
-                                  'path', StdExpPathPrinter)
+                                  'path', StdPathPrinter)
     libstdcxx_printer.add_version('std::filesystem::__cxx11::',
-                                  'path', StdExpPathPrinter)
+                                  'path', StdPathPrinter)
 
     # C++17 components
     libstdcxx_printer.add_version('std::',
index 06d882cf4de9191e37b8f79bd4bed1d025f85818..e9c78924b8e23b2a73bdd18aa7721303c686b1da 100644 (file)
 #endif
 
 #include <filesystem>
-#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
-# include <algorithm>
-#endif
+#include <algorithm>
+#include <bits/stl_uninitialized.h>
 
 namespace fs = std::filesystem;
 using fs::path;
 
-constexpr path::value_type path::preferred_separator;
+static inline bool is_dir_sep(path::value_type ch)
+{
+#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
+    return ch == L'/' || ch == path::preferred_separator;
+#else
+    return ch == '/';
+#endif
+}
+
+struct path::_Parser
+{
+  using string_view_type = std::basic_string_view<value_type>;
+
+  struct cmpt
+  {
+    string_view_type str;
+    _Type type = _Type::_Multi;
+
+    bool valid() const { return type != _Type::_Multi; }
+  };
+
+  string_view_type input;
+  string_view_type::size_type pos = 0;
+  size_t origin;
 
+  _Parser(string_view_type s, size_t o = 0) : input(s), origin(o) { }
+
+  pair<cmpt, cmpt> root_path() noexcept
+  {
+    pos = 0;
+    pair<cmpt, cmpt> root;
+
+    const size_t len = input.size();
+
+    // look for root name or root directory
+    if (is_dir_sep(input[0]))
+      {
+#ifdef __CYGWIN__
+       // look for root name, such as "//foo"
+       if (len > 2 && input[1] == input[0])
+         {
+           if (!is_dir_sep(input[2]))
+             {
+               // got root name, find its end
+               pos = 3;
+               while (pos < len && !is_dir_sep(input[pos]))
+                 ++pos;
+               root.first.str = input.substr(0, pos);
+               root.first.type = _Type::_Root_name;
+
+               if (pos < len) // also got root directory
+                 {
+                   root.second.str = input.substr(pos, 1);
+                   root.second.type = _Type::_Root_dir;
+                   ++pos;
+                 }
+             }
+           else
+             {
+               // got something like "///foo" which is just a root directory
+               // composed of multiple redundant directory separators
+               root.first.str = input.substr(0, 1);
+               root.first.type = _Type::_Root_dir;
+               pos += 2;
+             }
+         }
+       else
+#endif
+         {
+           root.first.str = input.substr(0, 1);
+           root.first.type = _Type::_Root_dir;
+           ++pos;
+         }
+       // Find the start of the first filename
+       while (pos < len && is_dir_sep(input[pos]))
+         ++pos;
+      }
 #ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
+    else if (len > 1 && input[1] == L':')
+      {
+       // got disk designator
+       root.first.str = input.substr(0, 2);
+       root.first.type = _Type::_Root_name;
+       if (len > 2 && is_dir_sep(input[2]))
+         {
+           root.second.str = input.substr(2, 1);
+           root.second.type = _Type::_Root_dir;
+         }
+       pos = input.find_first_not_of(L"/\\", 2);
+      }
+#endif
+    return root;
+  }
+
+  cmpt next() noexcept
+  {
+#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
+    string_view_type sep = L"/\\";
+#else
+    char sep = '/';
+#endif
+
+    cmpt f;
+    pos = input.find_first_not_of(sep, pos);
+    if (pos != input.npos)
+      {
+       const auto end = input.find_first_of(sep, pos);
+       f.str = input.substr(pos, end - pos);
+       f.type = _Type::_Filename;
+       pos = end;
+      }
+    return f;
+  }
+
+  string_view_type::size_type
+  offset(const cmpt& c) const noexcept
+  { return origin + c.str.data() - input.data(); }
+};
+
+struct path::_List::_Impl
+{
+  using value_type = _Cmpt;
+
+  _Impl(int cap) : _M_size(0), _M_capacity(cap) { }
+
+  alignas(value_type) int _M_size;
+  int _M_capacity;
+
+  using iterator = value_type*;
+  using const_iterator = const value_type*;
+
+  iterator begin() { return reinterpret_cast<value_type*>(this + 1); }
+  iterator end() { return begin() + size(); }
+
+  const_iterator begin() const
+  { return reinterpret_cast<const value_type*>(this + 1); }
+  const_iterator end() const { return begin() + size(); }
+
+  const value_type& front() const { return *begin(); }
+  const value_type& back() const { return end()[-1]; }
+
+  int size() const { return _M_size; }
+  int capacity() const { return _M_capacity; }
+  bool empty() const { return _M_size == 0; }
+
+  void clear() { std::destroy_n(begin(), _M_size); _M_size = 0; }
+
+  void erase(const_iterator cpos)
+  {
+    iterator pos = begin() + (cpos - begin());
+    if (pos + 1 != end())
+      std::move(pos + 1, end(), pos);
+    pos->~_Cmpt();
+    --_M_size;
+  }
+
+  void erase(const_iterator cfirst, const_iterator clast)
+  {
+    iterator first = begin() + (cfirst - begin());
+    iterator last = begin() + (clast - begin());
+    if (last != end())
+      std::move(last, end(), first);
+    std::destroy(first + (end() - last), end());
+    _M_size -= last - first;
+  }
+
+  unique_ptr<_Impl, _Impl_deleter> copy() const
+  {
+    const auto n = size();
+    void* p = ::operator new(sizeof(_Impl) + n * sizeof(value_type));
+    unique_ptr<_Impl, _Impl_deleter> newptr(::new (p) _Impl{n});
+    std::uninitialized_copy_n(begin(), n, newptr->begin());
+    newptr->_M_size = n;
+    return newptr;
+  }
+
+  // Clear the lowest two bits from the pointer (i.e. remove the _Type value)
+  static _Impl* notype(_Impl* p)
+  {
+    constexpr uintptr_t mask = ~(uintptr_t)0x3;
+    return reinterpret_cast<_Impl*>(reinterpret_cast<uintptr_t>(p) & mask);
+  }
+};
+
+void path::_List::_Impl_deleter::operator()(_Impl* p) const noexcept
+{
+  p = _Impl::notype(p);
+  if (p)
+    {
+      __glibcxx_assert(p->_M_size <= p->_M_capacity);
+      p->clear();
+      ::operator delete(p, sizeof(*p) + p->_M_capacity * sizeof(value_type));
+    }
+}
+
+path::_List::_List() : _M_impl(reinterpret_cast<_Impl*>(_Type::_Filename)) { }
+
+path::_List::_List(const _List& other)
+{
+  if (!other.empty())
+    _M_impl = other._M_impl->copy();
+  else
+    type(other.type());
+}
+
+path::_List&
+path::_List::operator=(const _List& other)
+{
+  if (!other.empty())
+    {
+      // copy in-place if there is capacity
+      const int newsize = other._M_impl->size();
+      auto impl = _Impl::notype(_M_impl.get());
+      if (impl && impl->capacity() >= newsize)
+       {
+         const int oldsize = impl->_M_size;
+         auto to = impl->begin();
+         auto from = other._M_impl->begin();
+         const int minsize = std::min(newsize, oldsize);
+         for (int i = 0; i < minsize; ++i)
+           to[i]._M_pathname.reserve(from[i]._M_pathname.length());
+         if (newsize > oldsize)
+           {
+             std::uninitialized_copy_n(to + oldsize, newsize - oldsize,
+                                       from + oldsize);
+             impl->_M_size = newsize;
+           }
+         else if (newsize < oldsize)
+           impl->erase(impl->begin() + newsize, impl->end());
+         std::copy_n(from, minsize, to);
+         type(_Type::_Multi);
+       }
+      else
+       _M_impl = other._M_impl->copy();
+    }
+  else
+    {
+      clear();
+      type(other.type());
+    }
+  return *this;
+}
+
+inline void
+path::_List::type(_Type t) noexcept
+{
+  auto val = reinterpret_cast<uintptr_t>(_Impl::notype(_M_impl.release()));
+  _M_impl.reset(reinterpret_cast<_Impl*>(val | (unsigned char)t));
+}
+
+inline int
+path::_List::size() const noexcept
+{
+  if (auto* ptr = _Impl::notype(_M_impl.get()))
+    return ptr->size();
+  return 0;
+}
+
+inline int
+path::_List::capacity() const noexcept
+{
+  if (auto* ptr = _Impl::notype(_M_impl.get()))
+    return ptr->capacity();
+  return 0;
+}
+
+inline bool
+path::_List::empty() const noexcept
+{
+  return size() == 0;
+}
+
+inline auto
+path::_List::begin() noexcept
+-> iterator
+{
+  __glibcxx_assert(!empty());
+  if (auto* ptr = _Impl::notype(_M_impl.get()))
+    return ptr->begin();
+  return nullptr;
+}
+
+inline auto
+path::_List::end() noexcept
+-> iterator
+{
+  __glibcxx_assert(!empty());
+  if (auto* ptr = _Impl::notype(_M_impl.get()))
+    return ptr->end();
+  return nullptr;
+}
+
+auto
+path::_List::begin() const noexcept
+-> const_iterator
+{
+  __glibcxx_assert(!empty());
+  if (auto* ptr = _Impl::notype(_M_impl.get()))
+    return ptr->begin();
+  return nullptr;
+}
+
+auto
+path::_List::end() const noexcept
+-> const_iterator
+{
+  __glibcxx_assert(!empty());
+  if (auto* ptr = _Impl::notype(_M_impl.get()))
+    return ptr->end();
+  return nullptr;
+}
+
+inline auto
+path::_List::front() noexcept
+-> value_type&
+{
+  return *_M_impl->begin();
+}
+
+inline auto
+path::_List::back() noexcept
+-> value_type&
+{
+  return _M_impl->begin()[_M_impl->size() - 1];
+}
+
+inline auto
+path::_List::front() const noexcept
+-> const value_type&
+{
+  return *_M_impl->begin();
+}
+
+inline auto
+path::_List::back() const noexcept
+-> const value_type&
+{
+  return _M_impl->begin()[_M_impl->size() - 1];
+}
+
+inline void
+path::_List::erase(const_iterator pos)
+{
+  _M_impl->erase(pos);
+}
+
+inline void
+path::_List::erase(const_iterator first, const_iterator last)
+{
+  _M_impl->erase(first, last);
+}
+
+inline void
+path::_List::clear()
+{
+  if (auto ptr = _Impl::notype(_M_impl.get()))
+    ptr->clear();
+}
+
+void
+path::_List::reserve(int newcap, bool exact = false)
+{
+  // __glibcxx_assert(type() == _Type::_Multi);
+
+  _Impl* curptr = _Impl::notype(_M_impl.get());
+
+  int curcap = curptr ? curptr->capacity() : 0;
+
+  if (curcap < newcap)
+    {
+      if (!exact && newcap < int(1.5 * curcap))
+       newcap = 1.5 * curcap;
+
+      void* p = ::operator new(sizeof(_Impl) + newcap * sizeof(value_type));
+      std::unique_ptr<_Impl, _Impl_deleter> newptr(::new(p) _Impl{newcap});
+      const int cursize = curptr ? curptr->size() : 0;
+      if (cursize)
+       {
+         std::uninitialized_move_n(curptr->begin(), cursize, newptr->begin());
+         newptr->_M_size = cursize;
+       }
+      std::swap(newptr, _M_impl);
+    }
+}
+
+path&
+path::operator=(const path& p)
+{
+  _M_pathname.reserve(p._M_pathname.length());
+  _M_cmpts = p._M_cmpts;       // might throw
+  _M_pathname = p._M_pathname; // won't throw because we reserved enough space
+  return *this;
+}
+
 path&
 path::operator/=(const path& __p)
 {
+#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
   if (__p.is_absolute()
       || (__p.has_root_name() && __p.root_name() != root_name()))
     return operator=(__p);
@@ -50,10 +441,10 @@ path::operator/=(const path& __p)
   if (__p.has_root_directory())
     {
       // Remove any root directory and relative path
-      if (_M_type != _Type::_Root_name)
+      if (_M_type() != _Type::_Root_name)
        {
          if (!_M_cmpts.empty()
-             && _M_cmpts.front()._M_type == _Type::_Root_name)
+             && _M_cmpts.front()._M_type() == _Type::_Root_name)
            __lhs = _M_cmpts.front()._M_pathname;
          else
            __lhs = {};
@@ -64,14 +455,14 @@ path::operator/=(const path& __p)
 
   basic_string_view<value_type> __rhs = __p._M_pathname;
   // Omit any root-name from the generic format pathname:
-  if (__p._M_type == _Type::_Root_name)
+  if (__p._M_type() == _Type::_Root_name)
     __rhs = {};
   else if (!__p._M_cmpts.empty()
-      && __p._M_cmpts.front()._M_type == _Type::_Root_name)
+      && __p._M_cmpts.front()._M_type() == _Type::_Root_name)
     __rhs.remove_prefix(__p._M_cmpts.front()._M_pathname.size());
 
   const size_t __len = __lhs.size() + (int)__add_sep + __rhs.size();
-  const size_t __maxcmpts = _M_cmpts.size() + __p._M_cmpts.size();
+  const int __maxcmpts = _M_cmpts.size() + __p._M_cmpts.size();
   if (_M_pathname.capacity() < __len || _M_cmpts.capacity() < __maxcmpts)
     {
       // Construct new path and swap (strong exception-safety guarantee).
@@ -90,36 +481,688 @@ path::operator/=(const path& __p)
       if (__add_sep)
        _M_pathname += preferred_separator;
       _M_pathname += __rhs;
-      _M_split_cmpts();
+      __try
+       {
+         _M_split_cmpts();
+       }
+      __catch (...)
+       {
+         __try
+           {
+             // try to restore original state
+             _M_pathname.resize(__lhs.length());
+             _M_split_cmpts();
+           }
+         __catch (...)
+           {
+             // give up, basic exception safety guarantee only:
+             clear();
+             __throw_exception_again;
+           }
+       }
     }
+#else
+  // POSIX version is simpler than the specification in the standard,
+  // as any path with root-name or root-dir is absolute.
+
+  if (__p.is_absolute() || this->empty())
+    {
+      return operator=(__p);
+    }
+
+  using string_view_type = basic_string_view<value_type>;
+
+  string_view_type sep;
+  if (has_filename())
+    sep = { &preferred_separator, 1 };  // need to add a separator
+#ifdef __CYGWIN__
+  else if (_M_type() == _Type::_Root_name) // root-name with no root-dir
+    sep = { &preferred_separator, 1 };  // need to add a separator
+#endif
+  else if (__p.empty())
+    return *this;                          // nothing to do
+
+  const auto orig_pathlen = _M_pathname.length();
+  const auto orig_size = _M_cmpts.size();
+  const auto orig_type = _M_type();
+
+  int capacity = 0;
+  if (_M_type() == _Type::_Multi)
+    capacity += _M_cmpts.size();
+  else if (!empty())
+    capacity += 1;
+  if (__p._M_type() == _Type::_Multi)
+    capacity += __p._M_cmpts.size();
+  else if (!__p.empty() || !sep.empty())
+    capacity += 1;
+
+  if (orig_type == _Type::_Multi)
+    {
+      const int curcap = _M_cmpts._M_impl->capacity();
+      if (capacity > curcap)
+       capacity = std::max(capacity, (int) (curcap * 1.5));
+    }
+
+  _M_pathname.reserve(_M_pathname.length() + sep.length()
+                     + __p._M_pathname.length());
+
+  __try
+    {
+      _M_pathname += sep;
+      const auto basepos = _M_pathname.length();
+      _M_pathname += __p.native();
+
+      _M_cmpts.type(_Type::_Multi);
+      _M_cmpts.reserve(capacity);
+      _Cmpt* output = _M_cmpts._M_impl->end();
+
+      if (orig_type == _Type::_Multi)
+       {
+         // Remove empty final component
+         if (_M_cmpts._M_impl->back().empty())
+           _M_cmpts._M_impl->erase(--output);
+       }
+      else if (orig_pathlen != 0)
+       {
+         // Create single component from original path
+         string_view_type s(_M_pathname.data(), orig_pathlen);
+         ::new(output++) _Cmpt(s, orig_type, 0);
+         ++_M_cmpts._M_impl->_M_size;
+       }
+
+      if (__p._M_type() == _Type::_Multi)
+       {
+         for (auto& c : *__p._M_cmpts._M_impl)
+           {
+             ::new(output++) _Cmpt(c._M_pathname, _Type::_Filename,
+                                   c._M_pos + basepos);
+             ++_M_cmpts._M_impl->_M_size;
+           }
+       }
+      else if (!__p.empty() || !sep.empty())
+       {
+         __glibcxx_assert(__p._M_type() == _Type::_Filename);
+         ::new(output) _Cmpt(__p._M_pathname, __p._M_type(), basepos);
+         ++_M_cmpts._M_impl->_M_size;
+       }
+    }
+  __catch (...)
+    {
+      _M_pathname.resize(orig_pathlen);
+      if (orig_type == _Type::_Multi)
+       _M_cmpts.erase(_M_cmpts.begin() + orig_size, _M_cmpts.end());
+      else
+       _M_cmpts.clear();
+      _M_cmpts.type(orig_type);
+      __throw_exception_again;
+    }
+#endif
   return *this;
 }
+
+// [fs.path.append]
+void
+path::_M_append(basic_string_view<value_type> s)
+{
+  _Parser parser(s);
+  auto root_path = parser.root_path();
+
+#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
+  bool is_absolute = root_path.second.type == _Type::_Root_dir;
+  bool has_root_name = root_path.first.type == _Type::_Root_name;
+  if (is_absolute || (has_root_name && root_path.first.str != root_name()))
+    {
+      operator=(s);
+      return;
+    }
+
+  basic_string_view<value_type> lhs = _M_pathname;
+  bool add_sep = false;
+
+  bool has_root_directory = root_path.first.type == _Type::_Root_dir
+    || root_path.second.type == _Type::_Root_dir;
+
+  if (has_root_directory)
+    {
+      // Remove any root directory and relative path
+      if (_M_type() != _Type::_Root_name)
+       {
+         if (!_M_cmpts.empty()
+             && _M_cmpts.front()._M_type() == _Type::_Root_name)
+           lhs = _M_cmpts.front()._M_pathname;
+         else
+           lhs = {};
+       }
+    }
+  else if (has_filename() || (!has_root_directory && is_absolute))
+    add_sep = true;
+
+  basic_string_view<value_type> rhs = s;
+  // Omit any root-name from the generic format pathname:
+  if (has_root_name)
+    rhs.remove_prefix(root_path.first.str.length());
+
+  // Construct new path and swap (strong exception-safety guarantee).
+  string_type tmp;
+  tmp.reserve(lhs.size() + (int)add_sep + rhs.size());
+  tmp = lhs;
+  if (add_sep)
+    tmp += preferred_separator;
+  tmp += rhs;
+  path newp = std::move(tmp);
+  swap(newp);
+#else
+
+  bool is_absolute = root_path.first.type == _Type::_Root_dir
+    || root_path.second.type == _Type::_Root_dir;
+  if (is_absolute || this->empty())
+    {
+      operator=(s);
+      return;
+    }
+
+  const auto orig_pathlen = _M_pathname.length();
+  const auto orig_size = _M_cmpts.size();
+  const auto orig_type = _M_type();
+
+  basic_string_view<value_type> sep;
+  if (has_filename())
+    sep = { &preferred_separator, 1 };  // need to add a separator
+#ifdef __CYGWIN__
+  else if (_M_type() == _Type::_Root_name) // root-name with no root-dir
+    sep = { &preferred_separator, 1 };  // need to add a separator
+#endif
+  else if (s.empty())
+    return;                        // nothing to do
+
+  // Copy the input into _M_pathname:
+  _M_pathname += s;
+  _M_pathname.insert(orig_pathlen, sep);
+  // Update s to refer to the new copy (this ensures s is not a dangling
+  // reference to deallocated characters, in the case where it was referring
+  // into _M_pathname or a member of _M_cmpts).
+  s = _M_pathname;
+  const auto orig_pathname = s.substr(0, orig_pathlen);
+  s.remove_prefix(orig_pathlen + sep.length());
+
+  parser.input = s; // reset parser to use updated string view
+  const auto basepos = orig_pathname.length() + sep.length();
+  parser.origin = basepos;
+
+  std::array<_Parser::cmpt, 64> buf;
+  auto next = buf.begin();
+
+  int capacity = 0;
+  if (_M_type() == _Type::_Multi)
+    capacity += _M_cmpts.size();
+  else if (!empty())
+    capacity += 1;
+
+  auto cmpt = parser.next();
+  if (cmpt.valid())
+    {
+      do
+       {
+         *next++ = cmpt;
+         cmpt = parser.next();
+       }
+      while (cmpt.valid() && next != buf.end());
+
+      capacity += next - buf.begin();
+      if (cmpt.valid()) // filled buffer before parsing whole input
+       {
+         ++capacity;
+         _Parser parser2(parser);
+         while (parser2.next().valid())
+           ++capacity;
+       }
+
+      if (s.back() == '/')
+       ++capacity;
+    }
+  else if (!sep.empty())
+    ++capacity;
+
+  __try
+    {
+      _M_cmpts.type(_Type::_Multi);
+      _M_cmpts.reserve(capacity);
+      _Cmpt* output = _M_cmpts._M_impl->end();
+
+      if (orig_type == _Type::_Multi)
+       {
+         // Remove empty final component
+         if (_M_cmpts._M_impl->back().empty())
+           _M_cmpts._M_impl->erase(--output);
+       }
+      else if (orig_pathlen != 0)
+       {
+         // Create single component from original path
+         ::new(output++) _Cmpt(orig_pathname, orig_type, 0);
+         ++_M_cmpts._M_impl->_M_size;
+       }
+
+      if (next != buf.begin())
+       {
+         for (auto it = buf.begin(); it != next; ++it)
+           {
+             auto c = *it;
+             ::new(output++) _Cmpt(c.str, c.type, parser.offset(c));
+             ++_M_cmpts._M_impl->_M_size;
+           }
+         for (auto c = parser.next(); c.valid(); c = parser.next())
+           {
+             ::new(output++) _Cmpt(c.str, c.type, parser.offset(c));
+             ++_M_cmpts._M_impl->_M_size;
+           }
+
+         if (s.back() == '/')
+           {
+             ::new(output++) _Cmpt({}, _Type::_Filename, _M_pathname.length());
+             ++_M_cmpts._M_impl->_M_size;
+           }
+       }
+      else if (!sep.empty())
+       {
+         // Empty filename at the end:
+         ::new(output) _Cmpt({}, _Type::_Filename, basepos);
+         ++_M_cmpts._M_impl->_M_size;
+       }
+    }
+  __catch (...)
+    {
+      _M_pathname.resize(orig_pathlen);
+      if (orig_type == _Type::_Multi)
+       _M_cmpts.erase(_M_cmpts.begin() + orig_size, _M_cmpts.end());
+      else
+       _M_cmpts.clear();
+      _M_cmpts.type(orig_type);
+      __throw_exception_again;
+    }
+#endif
+}
+
+// [fs.path.concat]
+path&
+path::operator+=(const path& p)
+{
+  if (p.empty())
+    return *this;
+
+  if (this->empty())
+    {
+      operator=(p);
+      return *this;
+    }
+
+  const auto orig_pathlen = _M_pathname.length();
+  const auto orig_type = _M_type();
+  const auto orig_size = _M_cmpts.size();
+  int orig_filenamelen = -1;
+  basic_string_view<value_type> extra;
+
+  // Ensure that '_M_pathname += p._M_pathname' won't throw:
+  _M_pathname.reserve(orig_pathlen + p._M_pathname.length());
+
+  _Cmpt c;
+  _Cmpt* it = nullptr;
+  _Cmpt* last = nullptr;
+  if (p._M_type() == _Type::_Multi)
+    {
+      it = p._M_cmpts._M_impl->begin();
+      last = p._M_cmpts._M_impl->end();
+    }
+  else
+    {
+      c = _Cmpt(p._M_pathname, p._M_type(), 0);
+      it = &c;
+      last = it + 1;
+    }
+
+  if (it->_M_type() == _Type::_Filename)
+    {
+      // See if there's a filename or root-name at the end of the original path
+      // that we can add to.
+      if (_M_type() == _Type::_Filename)
+       {
+         if (p._M_type() == _Type::_Filename)
+           {
+             // Simplest case where we just add the whole of p to the
+             // original path.
+             _M_pathname += p._M_pathname;
+             return *this;
+           }
+         // Only the first component of s should be appended, do so below:
+         extra = it->_M_pathname;
+         ++it;
+       }
+      else if (_M_type() == _Type::_Multi
+         && _M_cmpts.back()._M_type() == _Type::_Filename)
+       {
+         auto& back = _M_cmpts.back();
+         if (p._M_type() == _Type::_Filename)
+           {
+             basic_string_view<value_type> s = p._M_pathname;
+             back._M_pathname += s;
+             _M_pathname += s;
+             return *this;
+           }
+
+         orig_filenamelen = back._M_pathname.length();
+         back._M_pathname += it->_M_pathname;
+         extra = it->_M_pathname;
+         ++it;
+       }
+    }
+  else if (is_dir_sep(_M_pathname.back()) && _M_type() == _Type::_Multi
+      && _M_cmpts.back()._M_type() == _Type::_Filename)
+    orig_filenamelen = 0; // current path has empty filename at end
+
+  // TODO handle "//rootname" + "foo" case for Cygwin.
+
+  int capacity = 0;
+  if (_M_type() == _Type::_Multi)
+    capacity += _M_cmpts.size();
+  else
+    capacity += 1;
+  if (p._M_type() == _Type::_Multi)
+    capacity += p._M_cmpts.size();
+  else
+    capacity += 1;
+
+  __try
+    {
+      _M_cmpts.type(_Type::_Multi);
+      _M_cmpts.reserve(capacity);
+      _Cmpt* output = _M_cmpts._M_impl->end();
+
+      if (orig_type != _Type::_Multi)
+       {
+         // Create single component from original path
+         auto ptr = ::new(output++) _Cmpt({}, orig_type, 0);
+         ++_M_cmpts._M_impl->_M_size;
+         ptr->_M_pathname.reserve(_M_pathname.length() + extra.length());
+         ptr->_M_pathname = _M_pathname;
+         ptr->_M_pathname += extra;
+       }
+      else if (orig_filenamelen == 0 && it != last)
+       {
+         // Remove empty filename at end of original path.
+         _M_cmpts.erase(std::prev(output));
+       }
+
+      if (it != last && it->_M_type() == _Type::_Root_name)
+       {
+         basic_string_view<value_type> s = it->_M_pathname;
+         auto pos = orig_pathlen;
+#ifdef __CYGWIN__
+         s.remove_prefix(2);
+         pos += 2;
 #endif
+         ::new(output++) _Cmpt(s, _Type::_Filename, pos);
+         ++_M_cmpts._M_impl->_M_size;
+         ++it;
+       }
+
+      if (it != last && it->_M_type() == _Type::_Root_dir)
+       {
+         ++it;
+         if (it == last)
+           {
+             // This root-dir becomes a trailing slash
+             auto pos = _M_pathname.length() + p._M_pathname.length();
+             ::new(output++) _Cmpt({}, _Type::_Filename, pos);
+             ++_M_cmpts._M_impl->_M_size;
+           }
+       }
+
+      while (it != last)
+       {
+         auto pos = it->_M_pos + orig_pathlen;
+         ::new(output++) _Cmpt(it->_M_pathname, _Type::_Filename, pos);
+         ++_M_cmpts._M_impl->_M_size;
+         ++it;
+       }
+
+      _M_pathname += p._M_pathname;
+
+      if (is_dir_sep(_M_pathname.back()))
+       {
+         ::new(output++) _Cmpt({}, _Type::_Filename, _M_pathname.length());
+         ++_M_cmpts._M_impl->_M_size;
+       }
+      }
+  __catch (...)
+    {
+      _M_pathname.resize(orig_pathlen);
+      if (orig_type == _Type::_Multi)
+       {
+         if (_M_cmpts.size() > orig_size)
+           _M_cmpts.erase(_M_cmpts.begin() + orig_size, _M_cmpts.end());
+         if (orig_filenamelen != -1)
+           {
+             if (_M_cmpts.size() == orig_size)
+               {
+                 auto& back = _M_cmpts.back();
+                 back._M_pathname.resize(orig_filenamelen);
+                 if (orig_filenamelen == 0)
+                   back._M_pos = orig_pathlen;
+               }
+             else
+               {
+                 auto output = _M_cmpts._M_impl->end();
+                 ::new(output) _Cmpt({}, _Type::_Filename, orig_pathlen);
+                 ++_M_cmpts._M_impl->_M_size;
+               }
+           }
+       }
+      else
+       _M_cmpts.clear();
+      _M_cmpts.type(orig_type);
+      __throw_exception_again;
+    }
+  return *this;
+}
+
+// [fs.path.concat]
+void
+path::_M_concat(basic_string_view<value_type> s)
+{
+  if (s.empty())
+    return;
+
+  if (this->empty())
+    {
+      operator=(s);
+      return;
+    }
+
+  const auto orig_pathlen = _M_pathname.length();
+  const auto orig_type = _M_type();
+  const auto orig_size = _M_cmpts.size();
+  int orig_filenamelen = -1;
+  basic_string_view<value_type> extra;
+
+  // Copy the input into _M_pathname:
+  _M_pathname += s;
+  // Update s to refer to the new copy (this ensures s is not a dangling
+  // reference to deallocated characters, in the case where it was referring
+  // into _M_pathname or a member of _M_cmpts).
+  s = _M_pathname;
+  const auto orig_pathname = s.substr(0, orig_pathlen);
+  s.remove_prefix(orig_pathlen);
+
+  _Parser parser(s, orig_pathlen);
+  auto cmpt = parser.next();
+
+  if (cmpt.str.data() == s.data())
+    {
+      // See if there's a filename or root-name at the end of the original path
+      // that we can add to.
+      if (_M_type() == _Type::_Filename)
+       {
+         if (cmpt.str.length() == s.length())
+           {
+             // Simplest case where we just need to add the whole of s
+             // to the original path, which was already done above.
+             return;
+           }
+         // Only the first component of s should be appended, do so below:
+         extra = cmpt.str;
+         cmpt = {}; // so we don't process it again
+       }
+      else if (_M_type() == _Type::_Multi
+         && _M_cmpts.back()._M_type() == _Type::_Filename)
+       {
+         auto& back = _M_cmpts.back();
+         if (cmpt.str.length() == s.length())
+           {
+             back._M_pathname += s;
+             return;
+           }
+
+         orig_filenamelen = back._M_pathname.length();
+         back._M_pathname += cmpt.str;
+         extra = cmpt.str;
+         cmpt = {};
+       }
+    }
+  else if (is_dir_sep(orig_pathname.back()) && _M_type() == _Type::_Multi
+      && _M_cmpts.back()._M_type() == _Type::_Filename)
+    orig_filenamelen = 0; // original path had empty filename at end
+
+
+  // TODO handle "//rootname" + "foo" case for Cygwin.
+
+  std::array<_Parser::cmpt, 64> buf;
+  auto next = buf.begin();
+
+  if (cmpt.valid())
+    *next++ = cmpt;
+
+  cmpt = parser.next();
+  while (cmpt.valid() && next != buf.end())
+    {
+      *next++ = cmpt;
+      cmpt = parser.next();
+    }
+
+  int capacity = 0;
+  if (_M_type() == _Type::_Multi)
+    capacity += _M_cmpts.size();
+  else
+    capacity += 1;
+
+  capacity += next - buf.begin();
+
+  if (cmpt.valid()) // filled buffer before parsing whole input
+    {
+      ++capacity;
+      _Parser parser2(parser);
+      while (parser2.next().valid())
+       ++capacity;
+    }
+  if (is_dir_sep(s.back()))
+    ++capacity;
+
+  __try
+    {
+      _M_cmpts.type(_Type::_Multi);
+      _M_cmpts.reserve(capacity);
+      _Cmpt* output = _M_cmpts._M_impl->end();
+      auto it = buf.begin();
+
+      if (orig_type != _Type::_Multi)
+       {
+         // Create single component from original path
+         auto p = ::new(output++) _Cmpt({}, orig_type, 0);
+         ++_M_cmpts._M_impl->_M_size;
+         p->_M_pathname.reserve(orig_pathname.length() + extra.length());
+         p->_M_pathname = orig_pathname;
+         p->_M_pathname += extra;
+       }
+      else if (orig_filenamelen == 0)
+       {
+         // Replace empty filename at end of original path.
+         std::prev(output)->_M_pathname = it->str;
+         std::prev(output)->_M_pos = parser.offset(*it);
+         ++it;
+       }
+
+      while (it != next)
+       {
+         ::new(output++) _Cmpt(it->str, _Type::_Filename, parser.offset(*it));
+         ++_M_cmpts._M_impl->_M_size;
+         ++it;
+       }
+
+      if (next == buf.end())
+       {
+         while (cmpt.valid())
+           {
+             auto pos = parser.offset(cmpt);
+             ::new(output++) _Cmpt(cmpt.str, _Type::_Filename, pos);
+             ++_M_cmpts._M_impl->_M_size;
+             cmpt = parser.next();
+           }
+       }
+
+      if (is_dir_sep(s.back()))
+       {
+         // Empty filename at the end:
+         ::new(output++) _Cmpt({}, _Type::_Filename, _M_pathname.length());
+         ++_M_cmpts._M_impl->_M_size;
+       }
+    }
+  __catch (...)
+    {
+      _M_pathname.resize(orig_pathlen);
+      if (orig_type == _Type::_Multi)
+       {
+         _M_cmpts.erase(_M_cmpts.begin() + orig_size, _M_cmpts.end());
+         if (orig_filenamelen != -1)
+           {
+             auto& back = _M_cmpts.back();
+             back._M_pathname.resize(orig_filenamelen);
+             if (orig_filenamelen == 0)
+               back._M_pos = orig_pathlen;
+           }
+       }
+      else
+       _M_cmpts.clear();
+      _M_cmpts.type(orig_type);
+      __throw_exception_again;
+    }
+}
 
 path&
 path::remove_filename()
 {
-  if (_M_type == _Type::_Multi)
+  if (_M_type() == _Type::_Multi)
     {
       if (!_M_cmpts.empty())
        {
          auto cmpt = std::prev(_M_cmpts.end());
-         if (cmpt->_M_type == _Type::_Filename && !cmpt->empty())
+         if (cmpt->_M_type() == _Type::_Filename && !cmpt->empty())
            {
              _M_pathname.erase(cmpt->_M_pos);
              auto prev = std::prev(cmpt);
-             if (prev->_M_type == _Type::_Root_dir
-                 || prev->_M_type == _Type::_Root_name)
+             if (prev->_M_type() == _Type::_Root_dir
+                 || prev->_M_type() == _Type::_Root_name)
                {
                  _M_cmpts.erase(cmpt);
-                 _M_trim();
+                 if (_M_cmpts.size() == 1)
+                   {
+                     _M_cmpts.type(_M_cmpts.front()._M_type());
+                     _M_cmpts.clear();
+                   }
                }
              else
                cmpt->clear();
            }
        }
     }
-  else if (_M_type == _Type::_Filename)
+  else if (_M_type() == _Type::_Filename)
     clear();
   return *this;
 }
@@ -201,15 +1244,15 @@ path::compare(const path& p) const noexcept
 
   if (empty() && p.empty())
     return 0;
-  else if (_M_type == _Type::_Multi && p._M_type == _Type::_Multi)
+  else if (_M_type() == _Type::_Multi && p._M_type() == _Type::_Multi)
     return do_compare(_M_cmpts.begin(), _M_cmpts.end(),
                      p._M_cmpts.begin(), p._M_cmpts.end());
-  else if (_M_type == _Type::_Multi)
+  else if (_M_type() == _Type::_Multi)
     {
       CmptRef c[1] = { { &p } };
       return do_compare(_M_cmpts.begin(), _M_cmpts.end(), c, c+1);
     }
-  else if (p._M_type == _Type::_Multi)
+  else if (p._M_type() == _Type::_Multi)
     {
       CmptRef c[1] = { { this } };
       return do_compare(c, c+1, p._M_cmpts.begin(), p._M_cmpts.end());
@@ -222,9 +1265,9 @@ path
 path::root_name() const
 {
   path __ret;
-  if (_M_type == _Type::_Root_name)
+  if (_M_type() == _Type::_Root_name)
     __ret = *this;
-  else if (_M_cmpts.size() && _M_cmpts.begin()->_M_type == _Type::_Root_name)
+  else if (_M_cmpts.size() && _M_cmpts.begin()->_M_type() == _Type::_Root_name)
     __ret = *_M_cmpts.begin();
   return __ret;
 }
@@ -233,17 +1276,17 @@ path
 path::root_directory() const
 {
   path __ret;
-  if (_M_type == _Type::_Root_dir)
+  if (_M_type() == _Type::_Root_dir)
     {
-      __ret._M_type = _Type::_Root_dir;
+      __ret._M_cmpts.type(_Type::_Root_dir);
       __ret._M_pathname.assign(1, preferred_separator);
     }
   else if (!_M_cmpts.empty())
     {
       auto __it = _M_cmpts.begin();
-      if (__it->_M_type == _Type::_Root_name)
+      if (__it->_M_type() == _Type::_Root_name)
         ++__it;
-      if (__it != _M_cmpts.end() && __it->_M_type == _Type::_Root_dir)
+      if (__it != _M_cmpts.end() && __it->_M_type() == _Type::_Root_dir)
         __ret = *__it;
     }
   return __ret;
@@ -253,23 +1296,23 @@ path
 path::root_path() const
 {
   path __ret;
-  if (_M_type == _Type::_Root_name)
+  if (_M_type() == _Type::_Root_name)
     __ret = *this;
-  else if (_M_type == _Type::_Root_dir)
+  else if (_M_type() == _Type::_Root_dir)
     {
       __ret._M_pathname.assign(1, preferred_separator);
-      __ret._M_type = _Type::_Root_dir;
+      __ret._M_cmpts.type(_Type::_Root_dir);
     }
   else if (!_M_cmpts.empty())
     {
       auto __it = _M_cmpts.begin();
-      if (__it->_M_type == _Type::_Root_name)
+      if (__it->_M_type() == _Type::_Root_name)
         {
           __ret = *__it++;
-          if (__it != _M_cmpts.end() && __it->_M_type == _Type::_Root_dir)
+          if (__it != _M_cmpts.end() && __it->_M_type() == _Type::_Root_dir)
            __ret /= *__it;
         }
-      else if (__it->_M_type == _Type::_Root_dir)
+      else if (__it->_M_type() == _Type::_Root_dir)
         __ret = *__it;
     }
   return __ret;
@@ -279,14 +1322,14 @@ path
 path::relative_path() const
 {
   path __ret;
-  if (_M_type == _Type::_Filename)
+  if (_M_type() == _Type::_Filename)
     __ret = *this;
   else if (!_M_cmpts.empty())
     {
       auto __it = _M_cmpts.begin();
-      if (__it->_M_type == _Type::_Root_name)
+      if (__it->_M_type() == _Type::_Root_name)
         ++__it;
-      if (__it != _M_cmpts.end() && __it->_M_type == _Type::_Root_dir)
+      if (__it != _M_cmpts.end() && __it->_M_type() == _Type::_Root_dir)
         ++__it;
       if (__it != _M_cmpts.end())
         __ret.assign(_M_pathname.substr(__it->_M_pos));
@@ -314,9 +1357,9 @@ path::parent_path() const
 bool
 path::has_root_name() const
 {
-  if (_M_type == _Type::_Root_name)
+  if (_M_type() == _Type::_Root_name)
     return true;
-  if (!_M_cmpts.empty() && _M_cmpts.begin()->_M_type == _Type::_Root_name)
+  if (!_M_cmpts.empty() && _M_cmpts.begin()->_M_type() == _Type::_Root_name)
     return true;
   return false;
 }
@@ -324,14 +1367,14 @@ path::has_root_name() const
 bool
 path::has_root_directory() const
 {
-  if (_M_type == _Type::_Root_dir)
+  if (_M_type() == _Type::_Root_dir)
     return true;
   if (!_M_cmpts.empty())
     {
       auto __it = _M_cmpts.begin();
-      if (__it->_M_type == _Type::_Root_name)
+      if (__it->_M_type() == _Type::_Root_name)
         ++__it;
-      if (__it != _M_cmpts.end() && __it->_M_type == _Type::_Root_dir)
+      if (__it != _M_cmpts.end() && __it->_M_type() == _Type::_Root_dir)
         return true;
     }
   return false;
@@ -340,11 +1383,11 @@ path::has_root_directory() const
 bool
 path::has_root_path() const
 {
-  if (_M_type == _Type::_Root_name || _M_type == _Type::_Root_dir)
+  if (_M_type() == _Type::_Root_name || _M_type() == _Type::_Root_dir)
     return true;
   if (!_M_cmpts.empty())
     {
-      auto __type = _M_cmpts.front()._M_type;
+      auto __type = _M_cmpts.front()._M_type();
       if (__type == _Type::_Root_name || __type == _Type::_Root_dir)
         return true;
     }
@@ -354,14 +1397,14 @@ path::has_root_path() const
 bool
 path::has_relative_path() const
 {
-  if (_M_type == _Type::_Filename && !_M_pathname.empty())
+  if (_M_type() == _Type::_Filename && !_M_pathname.empty())
     return true;
   if (!_M_cmpts.empty())
     {
       auto __it = _M_cmpts.begin();
-      if (__it->_M_type == _Type::_Root_name)
+      if (__it->_M_type() == _Type::_Root_name)
         ++__it;
-      if (__it != _M_cmpts.end() && __it->_M_type == _Type::_Root_dir)
+      if (__it != _M_cmpts.end() && __it->_M_type() == _Type::_Root_dir)
         ++__it;
       if (__it != _M_cmpts.end() && !__it->_M_pathname.empty())
         return true;
@@ -383,9 +1426,9 @@ path::has_filename() const
 {
   if (empty())
     return false;
-  if (_M_type == _Type::_Filename)
+  if (_M_type() == _Type::_Filename)
     return !_M_pathname.empty();
-  if (_M_type == _Type::_Multi)
+  if (_M_type() == _Type::_Multi)
     {
       if (_M_pathname.back() == preferred_separator)
        return false;
@@ -436,7 +1479,7 @@ path::lexically_normal() const
     {
 #ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
       // Replace each slash character in the root-name
-      if (p._M_type == _Type::_Root_name || p._M_type == _Type::_Root_dir)
+      if (p._M_type() == _Type::_Root_name || p._M_type() == _Type::_Root_dir)
        {
          string_type s = p.native();
          std::replace(s.begin(), s.end(), L'/', L'\\');
@@ -477,7 +1520,7 @@ path::lexically_normal() const
                    {
                      ret._M_pathname.erase(elem._M_cur->_M_pos);
                      // Do we still have a trailing slash?
-                     if (std::prev(elem)->_M_type == _Type::_Filename)
+                     if (std::prev(elem)->_M_type() == _Type::_Filename)
                        ret._M_cmpts.erase(elem._M_cur);
                      else
                        ret._M_cmpts.erase(elem._M_cur, ret._M_cmpts.end());
@@ -560,12 +1603,12 @@ path::_M_find_extension() const
 {
   const string_type* s = nullptr;
 
-  if (_M_type == _Type::_Filename)
+  if (_M_type() == _Type::_Filename)
     s = &_M_pathname;
-  else if (_M_type == _Type::_Multi && !_M_cmpts.empty())
+  else if (_M_type() == _Type::_Multi && !_M_cmpts.empty())
     {
       const auto& c = _M_cmpts.back();
-      if (c._M_type == _Type::_Filename)
+      if (c._M_type() == _Type::_Filename)
        s = &c._M_pathname;
     }
 
@@ -586,120 +1629,88 @@ void
 path::_M_split_cmpts()
 {
   _M_cmpts.clear();
+
   if (_M_pathname.empty())
     {
-      _M_type = _Type::_Filename;
+      _M_cmpts.type(_Type::_Filename);
+      return;
+    }
+  if (_M_pathname.length() == 1 && _M_pathname[0] == preferred_separator)
+    {
+      _M_cmpts.type(_Type::_Root_dir);
       return;
     }
-  _M_type = _Type::_Multi;
 
-  size_t pos = 0;
-  const size_t len = _M_pathname.size();
+  _Parser parser(_M_pathname);
+
+  std::array<_Parser::cmpt, 64> buf;
+  auto next = buf.begin();
 
   // look for root name or root directory
-  if (_S_is_dir_sep(_M_pathname[0]))
+  auto root_path = parser.root_path();
+  if (root_path.first.valid())
     {
-#ifdef __CYGWIN__
-      // look for root name, such as "//foo"
-      if (len > 2 && _M_pathname[1] == _M_pathname[0])
+      *next++ = root_path.first;
+      if (root_path.second.valid())
+       *next++ = root_path.second;
+    }
+
+  bool got_at_least_one_filename = false;
+
+  auto cmpt = parser.next();
+  while (cmpt.valid())
+    {
+      got_at_least_one_filename = true;
+      do
        {
-         if (!_S_is_dir_sep(_M_pathname[2]))
-           {
-             // got root name, find its end
-             pos = 3;
-             while (pos < len && !_S_is_dir_sep(_M_pathname[pos]))
-               ++pos;
-             _M_add_root_name(pos);
-             if (pos < len) // also got root directory
-               _M_add_root_dir(pos);
-           }
-         else
-           {
-             // got something like "///foo" which is just a root directory
-             // composed of multiple redundant directory separators
-             _M_add_root_dir(0);
-           }
+         *next++ = cmpt;
+         cmpt = parser.next();
        }
-      else
-#endif
-        {
-         // got root directory
-         if (_M_pathname.find_first_not_of('/') == string_type::npos)
+      while (cmpt.valid() && next != buf.end());
+
+      if (next == buf.end())
+       {
+         _M_cmpts.type(_Type::_Multi);
+         _M_cmpts.reserve(_M_cmpts.size() + buf.size());
+         auto output = _M_cmpts._M_impl->end();
+         for (auto& c : buf)
            {
-             // entire path is just slashes
-             _M_type = _Type::_Root_dir;
-             return;
+             auto pos = c.str.data() - _M_pathname.data();
+             ::new(output++) _Cmpt(c.str, c.type, pos);
+             ++_M_cmpts._M_impl->_M_size;
            }
-         _M_add_root_dir(0);
-         ++pos;
+         next = buf.begin();
        }
     }
-#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
-  else if (len > 1 && _M_pathname[1] == L':')
+
+  // [fs.path.itr]/4
+  // An empty element, if trailing non-root directory-separator present.
+  if (got_at_least_one_filename && is_dir_sep(_M_pathname.back()))
     {
-      // got disk designator
-      _M_add_root_name(2);
-      if (len > 2 && _S_is_dir_sep(_M_pathname[2]))
-       _M_add_root_dir(2);
-      pos = 2;
+      next->str = { _M_pathname.data() + _M_pathname.length(), 0 };
+      next->type = _Type::_Filename;
+      ++next;
     }
-#endif
 
-  size_t back = pos;
-  while (pos < len)
+  if (auto n = next - buf.begin())
     {
-      if (_S_is_dir_sep(_M_pathname[pos]))
+      if (n == 1 && _M_cmpts.empty())
        {
-         if (back != pos)
-           _M_add_filename(back, pos - back);
-         back = ++pos;
+         _M_cmpts.type(buf.front().type);
+         return;
        }
-      else
-       ++pos;
-    }
 
-  if (back != pos)
-    _M_add_filename(back, pos - back);
-  else if (_S_is_dir_sep(_M_pathname.back()))
-    {
-      // [fs.path.itr]/4
-      // An empty element, if trailing non-root directory-separator present.
-      if (_M_cmpts.back()._M_type == _Type::_Filename)
+      _M_cmpts.type(_Type::_Multi);
+      _M_cmpts.reserve(_M_cmpts.size() + n, true);
+      auto output = _M_cmpts._M_impl->end();
+      for (int i = 0; i < n; ++i)
        {
-         pos = _M_pathname.size();
-         _M_cmpts.emplace_back(string_type(), _Type::_Filename, pos);
+         auto c = buf[i];
+         auto pos = c.str.data() - _M_pathname.data();
+         ::new(output++) _Cmpt(c.str, c.type, pos);
+         ++_M_cmpts._M_impl->_M_size;
        }
     }
-
-  _M_trim();
-}
-
-void
-path::_M_add_root_name(size_t n)
-{
-  _M_cmpts.emplace_back(_M_pathname.substr(0, n), _Type::_Root_name, 0);
-}
-
-void
-path::_M_add_root_dir(size_t pos)
-{
-  _M_cmpts.emplace_back(_M_pathname.substr(pos, 1), _Type::_Root_dir, pos);
-}
-
-void
-path::_M_add_filename(size_t pos, size_t n)
-{
-  _M_cmpts.emplace_back(_M_pathname.substr(pos, n), _Type::_Filename, pos);
-}
-
-void
-path::_M_trim()
-{
-  if (_M_cmpts.size() == 1)
-    {
-      _M_type = _M_cmpts.front()._M_type;
-      _M_cmpts.clear();
-    }
 }
 
 path::string_type
index df917c9c5e85f66cab8d25bcf27ea2a6c2fc2a82..e440ca921c7955e598afc41daaf21c6bea1a20f3 100644 (file)
@@ -112,6 +112,33 @@ test04()
 #endif
 }
 
+void
+test05()
+{
+  std::basic_string_view<path::value_type> s;
+
+  path p = "0/1/2/3/4/5/6";
+  // The string_view aliases the path's internal string:
+  s = p.native();
+  // Append that string_view, which must work correctly even though the
+  // internal string will be reallocated during the operation:
+  p /= s;
+  VERIFY( p.string() == "0/1/2/3/4/5/6/0/1/2/3/4/5/6" );
+
+  // Same again with a trailing slash:
+  path p2 = "0/1/2/3/4/5/";
+  s = p2.native();
+  p2 /= s;
+  VERIFY( p2.string() == "0/1/2/3/4/5/0/1/2/3/4/5/" );
+
+  // And aliasing one of the components of the path:
+  path p3 = "0/123456789/a";
+  path::iterator second = std::next(p3.begin());
+  s = second->native();
+  p3 /= s;
+  VERIFY( p3.string() == "0/123456789/a/123456789" );
+}
+
 int
 main()
 {
@@ -119,4 +146,5 @@ main()
   test02();
   test03();
   test04();
+  test05();
 }
index 67637890c7f7550cb181a36835d5ca5b194f3e13..eea9b6dc69b925353b164654845a2a1b026498be 100644 (file)
@@ -57,8 +57,36 @@ test01()
   VERIFY( p.filename().string() == file );
 }
 
+void
+test02()
+{
+  std::basic_string_view<path::value_type> s;
+
+  path p = "0/1/2/3/4/5/6";
+  // The string_view aliases the path's internal string:
+  s = p.native();
+  // Append that string_view, which must work correctly even though the
+  // internal string will be reallocated during the operation:
+  p += s;
+  VERIFY( p.string() == "0/1/2/3/4/5/60/1/2/3/4/5/6" );
+
+  // Same again with a trailing slash:
+  path p2 = "0/1/2/3/4/5/";
+  s = p2.native();
+  p2 += s;
+  VERIFY( p2.string() == "0/1/2/3/4/5/0/1/2/3/4/5/" );
+
+  // And aliasing one of the components of the path:
+  path p3 = "0/123456789";
+  path::iterator second = std::next(p3.begin());
+  s = second->native();
+  p3 += s;
+  VERIFY( p3.string() == "0/123456789123456789" );
+}
+
 int
 main()
 {
   test01();
+  test02();
 }