29cc80f4ec
The application of constexpr to __construct_at triggers weird linker errors when building LLVM with modules enabled and C++ < 20. > ld.lld: error: undefined hidden symbol: void* std::__1::__voidify[abi:nn190000]<llvm::sys::ProcessStatistics>(llvm::sys::ProcessStatistics&) >>>> referenced by construct_at.h:52 (/usr/local/bin/../include/c++/v1/__memory/construct_at.h:52) >>>> Program.cpp.o:(llvm::sys::Wait(llvm::sys::ProcessInfo const&, std::__1::optional<unsigned int>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>*, std::__1::optional<llvm::sys::ProcessStatistics>*, bool)) in archive lib/libLLVMSupport.a I suspect this is related to undefined behavior caused by the fact that construct_at is never really constexpr (which is UB NDR). I'm unsure how to meaningfully write a test for this, as I haven't been able to trigger it in smaller unit tests
129 lines
4.3 KiB
C++
129 lines
4.3 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___MEMORY_CONSTRUCT_AT_H
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#define _LIBCPP___MEMORY_CONSTRUCT_AT_H
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#include <__assert>
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#include <__config>
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#include <__iterator/access.h>
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#include <__memory/addressof.h>
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#include <__memory/voidify.h>
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#include <__type_traits/enable_if.h>
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#include <__type_traits/is_array.h>
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#include <__utility/declval.h>
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#include <__utility/forward.h>
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#include <__utility/move.h>
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#include <new>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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// construct_at
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#if _LIBCPP_STD_VER >= 20
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template <class _Tp, class... _Args, class = decltype(::new(std::declval<void*>()) _Tp(std::declval<_Args>()...))>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp* construct_at(_Tp* __location, _Args&&... __args) {
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_LIBCPP_ASSERT_NON_NULL(__location != nullptr, "null pointer given to construct_at");
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return ::new (std::__voidify(*__location)) _Tp(std::forward<_Args>(__args)...);
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}
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#endif
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template <class _Tp, class... _Args, class = decltype(::new(std::declval<void*>()) _Tp(std::declval<_Args>()...))>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp* __construct_at(_Tp* __location, _Args&&... __args) {
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#if _LIBCPP_STD_VER >= 20
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return std::construct_at(__location, std::forward<_Args>(__args)...);
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#else
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return _LIBCPP_ASSERT_NON_NULL(__location != nullptr, "null pointer given to construct_at"),
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::new (std::__voidify(*__location)) _Tp(std::forward<_Args>(__args)...);
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#endif
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}
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// destroy_at
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// The internal functions are available regardless of the language version (with the exception of the `__destroy_at`
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// taking an array).
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template <class _ForwardIterator>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator __destroy(_ForwardIterator, _ForwardIterator);
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template <class _Tp, __enable_if_t<!is_array<_Tp>::value, int> = 0>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __destroy_at(_Tp* __loc) {
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_LIBCPP_ASSERT_NON_NULL(__loc != nullptr, "null pointer given to destroy_at");
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__loc->~_Tp();
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}
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#if _LIBCPP_STD_VER >= 20
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template <class _Tp, __enable_if_t<is_array<_Tp>::value, int> = 0>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __destroy_at(_Tp* __loc) {
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_LIBCPP_ASSERT_NON_NULL(__loc != nullptr, "null pointer given to destroy_at");
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std::__destroy(std::begin(*__loc), std::end(*__loc));
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}
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#endif
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template <class _ForwardIterator>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
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__destroy(_ForwardIterator __first, _ForwardIterator __last) {
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for (; __first != __last; ++__first)
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std::__destroy_at(std::addressof(*__first));
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return __first;
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}
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template <class _BidirectionalIterator>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator
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__reverse_destroy(_BidirectionalIterator __first, _BidirectionalIterator __last) {
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while (__last != __first) {
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--__last;
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std::__destroy_at(std::addressof(*__last));
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}
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return __last;
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}
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#if _LIBCPP_STD_VER >= 17
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template <class _Tp, enable_if_t<!is_array_v<_Tp>, int> = 0>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void destroy_at(_Tp* __loc) {
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std::__destroy_at(__loc);
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}
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# if _LIBCPP_STD_VER >= 20
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template <class _Tp, enable_if_t<is_array_v<_Tp>, int> = 0>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void destroy_at(_Tp* __loc) {
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std::__destroy_at(__loc);
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}
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# endif
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template <class _ForwardIterator>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void destroy(_ForwardIterator __first, _ForwardIterator __last) {
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(void)std::__destroy(std::move(__first), std::move(__last));
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}
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template <class _ForwardIterator, class _Size>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator destroy_n(_ForwardIterator __first, _Size __n) {
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for (; __n > 0; (void)++__first, --__n)
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std::__destroy_at(std::addressof(*__first));
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return __first;
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}
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#endif // _LIBCPP_STD_VER >= 17
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___MEMORY_CONSTRUCT_AT_H
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