From: Jonathan Wakely <jwakely@redhat.com>
Date: Fri, 19 Sep 2025 15:03:11 +0000 (+0100)
Subject: libstdc++: Simplify std::erase functions for sequence containers
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b83c2e52a21c1882a149e89e5ab152c09a73fb30;p=thirdparty%2Fgcc.git

libstdc++: Simplify std::erase functions for sequence containers

This removes the use of std::ref that meant that __remove_if used an
indirection through the reference, which might be a pessimization. Users
can always use std::ref to pass expensive predicates into erase_if, but
we shouldn't do it unconditionally. We can std::move the predicate so
that if it's not cheap to copy and the user didn't use std::ref, then we
try to use a cheaper move instead of a copy.

There's no reason that std::erase shouldn't just be implemented by
forwarding to std::erase_if. I probably should have done that in
r12-4083-gacf3a21cbc26b3 when std::erase started to call __remove_if
directly.

libstdc++-v3/ChangeLog:

	* include/std/deque (erase_if): Move predicate instead of
	wrapping with std::ref.
	(erase): Forward to erase_if.
	* include/std/inplace_vector (erase_if, erase): Likewise.
	* include/std/string (erase_if, erase): Likewise.
	* include/std/vector (erase_if, erase): Likewise.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
---

diff --git a/libstdc++-v3/include/std/deque b/libstdc++-v3/include/std/deque
index 3b1a7dea2b1..c82f9dff286 100644
--- a/libstdc++-v3/include/std/deque
+++ b/libstdc++-v3/include/std/deque
@@ -66,7 +66,6 @@
 #include <bits/stl_construct.h>
 #include <bits/stl_uninitialized.h>
 #include <bits/stl_deque.h>
-#include <bits/refwrap.h>
 #include <bits/range_access.h>
 #include <bits/deque.tcc>
 
@@ -109,7 +108,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       const auto __osz = __cont.size();
       const auto __end = __ucont.end();
       auto __removed = std::__remove_if(__ucont.begin(), __end,
-					std::ref(__pred));
+					std::move(__pred));
       if (__removed != __end)
 	{
 	  __cont.erase(__niter_wrap(__cont.begin(), __removed),
@@ -124,22 +123,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	   typename _Up _GLIBCXX26_DEF_VAL_T(_Tp)>
     inline typename deque<_Tp, _Alloc>::size_type
     erase(deque<_Tp, _Alloc>& __cont, const _Up& __value)
-    {
-      using namespace __gnu_cxx;
-      _GLIBCXX_STD_C::deque<_Tp, _Alloc>& __ucont = __cont;
-      const auto __osz = __cont.size();
-      const auto __end = __ucont.end();
-      auto __removed = std::__remove_if(__ucont.begin(), __end,
-					__ops::__equal_to(__value));
-      if (__removed != __end)
-	{
-	  __cont.erase(__niter_wrap(__cont.begin(), __removed),
-		       __cont.end());
-	  return __osz - __cont.size();
-	}
+    { return std::erase_if(__cont, __gnu_cxx::__ops::__equal_to(__value)); }
 
-      return 0;
-    }
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // __cpp_lib_erase_if
diff --git a/libstdc++-v3/include/std/inplace_vector b/libstdc++-v3/include/std/inplace_vector
index b32aa4f3708..91ceace08f5 100644
--- a/libstdc++-v3/include/std/inplace_vector
+++ b/libstdc++-v3/include/std/inplace_vector
@@ -42,7 +42,6 @@
 #include <bits/ranges_base.h> // borrowed_iterator_t, __detail::__container_compatible_range
 #include <bits/ranges_util.h> // subrange
 #include <bits/ranges_uninitialized.h>
-#include <bits/refwrap.h>
 #include <bits/stl_construct.h>
 #include <bits/stl_uninitialized.h>
 #include <bits/stl_algo.h> // rotate
@@ -1343,7 +1342,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       const auto __osz = __cont.size();
       const auto __end = __cont.end();
       auto __removed = std::__remove_if(__cont.begin(), __end,
-					std::ref(__pred));
+					std::move(__pred));
       if (__removed != __end)
 	{
 	  __cont.erase(__niter_wrap(__cont.begin(), __removed),
@@ -1357,20 +1356,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp, size_t _Nm, typename _Up = _Tp>
     constexpr  size_t
     erase(inplace_vector<_Tp, _Nm>& __cont, const _Up& __value)
-    {
-      using namespace __gnu_cxx;
-      const auto __osz = __cont.size();
-      const auto __end = __cont.end();
-      auto __removed = std::__remove_if(__cont.begin(), __end,
-					__ops::__equal_to(__value));
-      if (__removed != __end)
-	{
-	  __cont.erase(__niter_wrap(__cont.begin(), __removed),
-		       __cont.end());
-	  return __osz - __cont.size();
-	}
-      return 0;
-    }
+    { return std::erase_if(__cont, __gnu_cxx::__ops::__equal_to(__value)); }
 
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
diff --git a/libstdc++-v3/include/std/string b/libstdc++-v3/include/std/string
index 74e0c7f2be5..4b84aeaa857 100644
--- a/libstdc++-v3/include/std/string
+++ b/libstdc++-v3/include/std/string
@@ -51,7 +51,6 @@
 #include <bits/stl_function.h> // For less
 #include <ext/numeric_traits.h>
 #include <bits/stl_algobase.h>
-#include <bits/refwrap.h>
 #include <bits/range_access.h>
 #include <bits/basic_string.h>
 #include <bits/basic_string.tcc>
@@ -104,7 +103,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       const auto __osz = __cont.size();
       const auto __end = __cont.end();
       auto __removed = std::__remove_if(__cont.begin(), __end,
-					std::ref(__pred));
+					std::move(__pred));
       __cont.erase(__removed, __end);
       return __osz - __cont.size();
     }
@@ -114,15 +113,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     _GLIBCXX20_CONSTEXPR
     inline typename basic_string<_CharT, _Traits, _Alloc>::size_type
     erase(basic_string<_CharT, _Traits, _Alloc>& __cont, const _Up& __value)
-    {
-      using namespace __gnu_cxx;
-      const auto __osz = __cont.size();
-      const auto __end = __cont.end();
-      auto __removed = std::__remove_if(__cont.begin(), __end,
-					__ops::__equal_to(__value));
-      __cont.erase(__removed, __end);
-      return __osz - __cont.size();
-    }
+    { return std::erase_if(__cont, __gnu_cxx::__ops::__equal_to(__value)); }
+
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // __cpp_lib_erase_if
diff --git a/libstdc++-v3/include/std/vector b/libstdc++-v3/include/std/vector
index 47105210bc0..cdc30cbff6d 100644
--- a/libstdc++-v3/include/std/vector
+++ b/libstdc++-v3/include/std/vector
@@ -67,7 +67,6 @@
 #include <bits/stl_uninitialized.h>
 #include <bits/stl_vector.h>
 #include <bits/stl_bvector.h>
-#include <bits/refwrap.h>
 #include <bits/range_access.h>
 
 #ifndef _GLIBCXX_EXPORT_TEMPLATE
@@ -122,7 +121,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       const auto __osz = __cont.size();
       const auto __end = __ucont.end();
       auto __removed = std::__remove_if(__ucont.begin(), __end,
-					std::ref(__pred));
+					std::move(__pred));
       if (__removed != __end)
 	{
 	  __cont.erase(__niter_wrap(__cont.begin(), __removed),
@@ -138,22 +137,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     _GLIBCXX20_CONSTEXPR
     inline typename vector<_Tp, _Alloc>::size_type
     erase(vector<_Tp, _Alloc>& __cont, const _Up& __value)
-    {
-      using namespace __gnu_cxx;
-      _GLIBCXX_STD_C::vector<_Tp, _Alloc>& __ucont = __cont;
-      const auto __osz = __cont.size();
-      const auto __end = __ucont.end();
-      auto __removed = std::__remove_if(__ucont.begin(), __end,
-					__ops::__equal_to(__value));
-      if (__removed != __end)
-	{
-	  __cont.erase(__niter_wrap(__cont.begin(), __removed),
-		       __cont.end());
-	  return __osz - __cont.size();
-	}
+    { return std::erase_if(__cont, __gnu_cxx::__ops::__equal_to(__value)); }
 
-      return 0;
-    }
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // __cpp_lib_erase_if