[{"id":3676895,"web_url":"http://patchwork.ozlabs.org/comment/3676895/","msgid":"","list_archive_url":null,"date":"2026-04-13T19:29:59","subject":"Re: [PATCH] libstdc++: Small allocator fixes","submitter":{"id":4329,"url":"http://patchwork.ozlabs.org/api/people/4329/","name":"Jonathan Wakely","email":"jwakely.gcc@gmail.com"},"content":"On Mon, 13 Apr 2026 at 20:05, Nathan Myers wrote:\n>\n> Since 2022, the constexpr branch of std::allocator::allocate(n)\n> has asked for the wrong size. More recently, allocator_traits\n> allocate_at_least has taken its allocator argument by value,\n> incorrectly.\n>\n> libstdc++-v3/ChangeLog:\n> * include/bits/allocator.h (allocate): When constexpr, allocate bytes.\n> * include/bits/alloc_traits.h (allocate_at_least): Take allocator\n> argument by reference, per spec.\n> ---\n> libstdc++-v3/include/bits/alloc_traits.h | 2 +-\n> libstdc++-v3/include/bits/allocator.h | 2 +-\n> 2 files changed, 2 insertions(+), 2 deletions(-)\n>\n> diff --git a/libstdc++-v3/include/bits/alloc_traits.h b/libstdc++-v3/include/bits/alloc_traits.h\n> index 2be8ed561d4..e4e0f1608de 100644\n> --- a/libstdc++-v3/include/bits/alloc_traits.h\n> +++ b/libstdc++-v3/include/bits/alloc_traits.h\n> @@ -670,7 +670,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n> * Returns `a.allocate_at_least(n)`.\n> */\n> [[nodiscard]] static constexpr auto\n> - allocate_at_least(allocator_type __a, size_type __n)\n> + allocate_at_least(allocator_type& __a, size_type __n)\n\nThis part is OK.\n\n> -> allocation_result\n> { return __a.allocate_at_least(__n); }\n> #endif\n> diff --git a/libstdc++-v3/include/bits/allocator.h b/libstdc++-v3/include/bits/allocator.h\n> index 9c22c805ebe..ae735605f67 100644\n> --- a/libstdc++-v3/include/bits/allocator.h\n> +++ b/libstdc++-v3/include/bits/allocator.h\n> @@ -200,7 +200,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n> {\n> if (__builtin_mul_overflow(__n, sizeof(_Tp), &__n))\n\nThis line performs n * sizeof(T) and stores the result in n (returning\ntrue if it overflows).\n\nSo it's equivalent the n *= sizeof(T).\n\n> std::__throw_bad_array_new_length();\n> - return static_cast<_Tp*>(::operator new(__n));\n> + return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));\n\nSo this is wrong.\n\n> }\n>\n> return __allocator_base<_Tp>::allocate(__n, 0);\n> --\n> 2.53.0\n>","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=Dfq9VI80;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; 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Mon, 13 Apr 2026\n 12:30:11 -0700 (PDT)","MIME-Version":"1.0","References":"<20260413190449.109479-1-ncm@cantrip.org>","In-Reply-To":"<20260413190449.109479-1-ncm@cantrip.org>","From":"Jonathan Wakely ","Date":"Mon, 13 Apr 2026 20:29:59 +0100","X-Gm-Features":"AQROBzCQpJYvd4MgGqH87xJO_s74yYkEOrvRNAMuYLxmKHmS8MZ3GzhmzM7VVBw","Message-ID":"\n ","Subject":"Re: [PATCH] libstdc++: Small allocator fixes","To":"Nathan Myers ","Cc":"gcc-patches@gcc.gnu.org, libstdc++@gcc.gnu.org","Content-Type":"text/plain; charset=\"UTF-8\"","X-BeenThere":"gcc-patches@gcc.gnu.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Gcc-patches mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"}}]