From 162c40a4c127cc55d701bb8760e17708d0ca2fe0 Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Tue, 28 Apr 2020 23:26:21 +0100 Subject: [PATCH] libstdc++: Fix regression in std::_Construct (PR 94831) By trying to reuse the existing std::_Construct function as a wrapper for std::construct_at I introduced regressions, because changing std::_Construct to return non-void made it ill-formed for array types. The solution is to revert _Construct to its former state, and change allocator_traits::construct to explicitly call construct_at instead. This decouples all the existing callers of _Construct from the new construct_at requirements. PR libstdc++/94831 * include/bits/alloc_traits.h (_S_construct): Restore placement new-expression for C++11/14/17 and call std::construct_at directly for C++20. * include/bits/stl_construct.h (_Construct): Revert to non-constexpr function returning void. * testsuite/20_util/specialized_algorithms/ uninitialized_value_construct/94831.cc: New test. * testsuite/23_containers/vector/cons/94831.cc: New test. --- libstdc++-v3/ChangeLog | 12 ++++++++ libstdc++-v3/include/bits/alloc_traits.h | 8 ++++- libstdc++-v3/include/bits/stl_construct.h | 20 +++++-------- .../uninitialized_value_construct/94831.cc | 29 +++++++++++++++++++ .../23_containers/vector/cons/94831.cc | 29 +++++++++++++++++++ 5 files changed, 84 insertions(+), 14 deletions(-) create mode 100644 libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct/94831.cc create mode 100644 libstdc++-v3/testsuite/23_containers/vector/cons/94831.cc diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index f2ddc5e4776..a5b6769ce88 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,15 @@ +2020-04-28 Jonathan Wakely + + PR libstdc++/94831 + * include/bits/alloc_traits.h (_S_construct): Restore placement + new-expression for C++11/14/17 and call std::construct_at directly + for C++20. + * include/bits/stl_construct.h (_Construct): Revert to non-constexpr + function returning void. + * testsuite/20_util/specialized_algorithms/ + uninitialized_value_construct/94831.cc: New test. + * testsuite/23_containers/vector/cons/94831.cc: New test. + 2020-04-28 Patrick Palka LWG 3433 subrange::advance(n) has UB when n < 0 diff --git a/libstdc++-v3/include/bits/alloc_traits.h b/libstdc++-v3/include/bits/alloc_traits.h index 061d353e3f0..6066f48d24c 100644 --- a/libstdc++-v3/include/bits/alloc_traits.h +++ b/libstdc++-v3/include/bits/alloc_traits.h @@ -253,7 +253,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION _S_construct(_Alloc&, _Tp* __p, _Args&&... __args) noexcept(noexcept(::new((void*)__p) _Tp(std::forward<_Args>(__args)...))) - { std::_Construct(__p, std::forward<_Args>(__args)...); } + { +#if __cplusplus <= 201703L + ::new((void*)__p) _Tp(std::forward<_Args>(__args)...); +#else + std::construct_at(__p, std::forward<_Args>(__args)...); +#endif + } template static _GLIBCXX14_CONSTEXPR auto diff --git a/libstdc++-v3/include/bits/stl_construct.h b/libstdc++-v3/include/bits/stl_construct.h index 5c9a84d9497..72a7cb4712c 100644 --- a/libstdc++-v3/include/bits/stl_construct.h +++ b/libstdc++-v3/include/bits/stl_construct.h @@ -65,9 +65,9 @@ * std::destroy_n, and the C++20 function std::construct_at. * It also provides std::_Construct, std::_Destroy,and std::_Destroy_n functions * which are defined in all standard modes and so can be used in C++98-14 code. - * The _Construct and _Destroy functions will dispatch to construct_at and - * destroy_at during constant evaluation, because calls to those functions are - * intercepted by the compiler to allow use in constant expressions. + * The _Destroy functions will dispatch to destroy_at during constant + * evaluation, because calls to that function are intercepted by the compiler + * to allow use in constant expressions. */ namespace std _GLIBCXX_VISIBILITY(default) @@ -104,23 +104,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION */ #if __cplusplus >= 201103L template - constexpr _Tp* + inline void _Construct(_Tp* __p, _Args&&... __args) - { -#if __cplusplus > 201703L - return std::construct_at(__p, std::forward<_Args>(__args)...); -#else - return ::new(static_cast(__p)) _Tp(std::forward<_Args>(__args)...); -#endif - } + { ::new(static_cast(__p)) _Tp(std::forward<_Args>(__args)...); } #else template - inline _T1* + inline void _Construct(_T1* __p, const _T2& __value) { // _GLIBCXX_RESOLVE_LIB_DEFECTS // 402. wrong new expression in [some_]allocator::construct - return ::new(static_cast(__p)) _T1(__value); + ::new(static_cast(__p)) _T1(__value); } #endif diff --git a/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct/94831.cc b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct/94831.cc new file mode 100644 index 00000000000..27506fae09f --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct/94831.cc @@ -0,0 +1,29 @@ +// Copyright (C) 2020 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// . + +// { dg-options "-std=gnu++17" } +// { dg-do compile { target c++17 } } + +#include + +void +test01() +{ + // PR libstdc++/94831 + float i[2]; + std::uninitialized_value_construct(&i, &i + 1); +} diff --git a/libstdc++-v3/testsuite/23_containers/vector/cons/94831.cc b/libstdc++-v3/testsuite/23_containers/vector/cons/94831.cc new file mode 100644 index 00000000000..72dfcaae9af --- /dev/null +++ b/libstdc++-v3/testsuite/23_containers/vector/cons/94831.cc @@ -0,0 +1,29 @@ +// Copyright (C) 2020 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// . + +// { dg-do compile { target c++11 } } + +#include + +void +test01() +{ + // PR libstdc++/94831.cc + // We allow this in C++11 and later as a GNU extension. + // FIXME: make it ill-formed when __STRICT_ANSI__ is defined. + std::vector v(1u); +} -- 2.30.2