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6f04937e1d
With gcc 10 and -std=c++20, we run into the same problem as reported in commit6feae66da1("[gdb/build, c++20] Handle deprecated std::allocator::construct"). The problem was fixed using: ... -template<typename T, typename A = std::allocator<T>> +template<typename T, + typename A +#if __cplusplus >= 202002L + = std::pmr::polymorphic_allocator<T> +#else + = std::allocator<T> +#endif + > ... but that doesn't work for gcc 10, because it defines __cplusplus differently: ... $ echo | g++-10 -E -dD -x c++ - -std=c++20 2>&1 | grep __cplusplus #define __cplusplus 201709L $ echo | g++-11 -E -dD -x c++ - -std=c++20 2>&1 | grep __cplusplus #define __cplusplus 202002L ... Fix this by using the library feature test macro __cpp_lib_polymorphic_allocator [1], which is undefined for c++17 and defined for c++20: ... $ echo | g++-10 -E -dD -x c++ - -include memory_resource -std=c++17 2>&1 \ | grep __cpp_lib_polymorphic_allocator $ echo | g++-10 -E -dD -x c++ - -include memory_resource -std=c++20 2>&1 \ | grep __cpp_lib_polymorphic_allocator #define __cpp_lib_polymorphic_allocator 201902L $ ... A similar problem exists for commit3173529d7d("[gdb/guile, c++20] Work around Werror=volatile in libguile.h"). Fix this by testing for 201709L instead. Tested on x86_64-linux, by building gdb with {gcc 10, clang 17.0.6} x {-std=c++17, -std=c++20}. PR build/32503 Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32503 Approved-By: Tom Tromey <tom@tromey.com> [1] https://en.cppreference.com/w/cpp/feature_test#cpp_lib_polymorphic_allocator
79 lines
2.3 KiB
C++
79 lines
2.3 KiB
C++
/* Copyright (C) 2017-2024 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef GDBSUPPORT_DEFAULT_INIT_ALLOC_H
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#define GDBSUPPORT_DEFAULT_INIT_ALLOC_H
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#if __has_include(<memory_resource>)
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#include <memory_resource>
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#endif
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namespace gdb {
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/* An allocator that default constructs using default-initialization
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rather than value-initialization. The idea is to use this when you
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don't want to default construct elements of containers of trivial
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types using zero-initialization. */
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/* Mostly as implementation convenience, this is implemented as an
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adapter that given an allocator A, overrides 'A::construct()'. 'A'
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defaults to std::allocator<T>. */
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template<typename T,
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typename A
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#ifdef __cpp_lib_polymorphic_allocator
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= std::pmr::polymorphic_allocator<T>
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#else
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= std::allocator<T>
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#endif
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>
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class default_init_allocator : public A
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{
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public:
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/* Pull in A's ctors. */
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using A::A;
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/* Override rebind. */
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template<typename U>
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struct rebind
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{
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/* A couple helpers just to make it a bit more readable. */
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typedef std::allocator_traits<A> traits_;
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typedef typename traits_::template rebind_alloc<U> alloc_;
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/* This is what we're after. */
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typedef default_init_allocator<U, alloc_> other;
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};
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/* Make the base allocator's construct method(s) visible. */
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using A::construct;
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/* .. and provide an override/overload for the case of default
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construction (i.e., no arguments). This is where we construct
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with default-init. */
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template <typename U>
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void construct (U *ptr)
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noexcept (std::is_nothrow_default_constructible<U>::value)
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{
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::new ((void *) ptr) U; /* default-init */
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}
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};
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} /* namespace gdb */
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#endif /* GDBSUPPORT_DEFAULT_INIT_ALLOC_H */
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