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From: "hubicka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/114821] _M_realloc_append should use memcpy instead
 of loop to copy data when possible
Date: Tue, 23 Apr 2024 12:38:21 +0000
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X-Bugzilla-Component: libstdc++
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Message-ID: <bug-114821-4-g92jmNyTnu@http.gcc.gnu.org/bugzilla/>
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114821

--- Comment #8 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
I had wrong noexcept specifier.  This version works, but I still need to in=
line
relocate_object_a into the loop

diff --git a/libstdc++-v3/include/bits/stl_uninitialized.h
b/libstdc++-v3/include/bits/stl_uninitialized.h
index 7f84da31578..f02d4fb878f 100644
--- a/libstdc++-v3/include/bits/stl_uninitialized.h
+++ b/libstdc++-v3/include/bits/stl_uninitialized.h
@@ -1100,8 +1100,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
          "relocation is only possible for values of the same type");
       _ForwardIterator __cur =3D __result;
       for (; __first !=3D __last; ++__first, (void)++__cur)
-       std::__relocate_object_a(std::__addressof(*__cur),
-                                std::__addressof(*__first), __alloc);
+       {
+         typedef std::allocator_traits<_Allocator> __traits;
+         __traits::construct(__alloc, std::__addressof(*__cur),
std::move(*std::__addressof(*__first)));
+         __traits::destroy(__alloc,
std::__addressof(*std::__addressof(*__first)));
+       }
       return __cur;
     }

@@ -1109,8 +1112,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template <typename _Tp, typename _Up>
     _GLIBCXX20_CONSTEXPR
     inline __enable_if_t<std::__is_bitwise_relocatable<_Tp>::value, _Tp*>
-    __relocate_a_1(_Tp* __first, _Tp* __last,
-                  _Tp* __result,
+    __relocate_a_1(_Tp* __restrict __first, _Tp* __last,
+                  _Tp* __restrict __result,
                   [[__maybe_unused__]] allocator<_Up>& __alloc) noexcept
     {
       ptrdiff_t __count =3D __last - __first;
@@ -1147,6 +1150,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
                                 std::__niter_base(__result), __alloc);
     }

+  template <typename _Tp, typename _Up>
+    _GLIBCXX20_CONSTEXPR
+    inline _Tp*
+    __relocate_a(_Tp* __restrict __first, _Tp* __last,
+                _Tp* __restrict __result,
+                allocator<_Up>& __alloc)
+    noexcept(noexcept(__relocate_a_1(__first, __last, __result, __alloc)))
+    {
+      return std::__relocate_a_1(__first, __last, __result, __alloc);
+    }
+
   /// @endcond
 #endif // C++11=