49 lines
1.8 KiB
C++
49 lines
1.8 KiB
C++
// Copyright (C) 2020-2023 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library 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 along
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// with this library; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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// { dg-options "-std=gnu++2a" }
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// { dg-do compile { target c++2a } }
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#include <span>
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#include <cstddef>
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#if __has_include(<sys/uio.h>)
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#include <sys/uio.h>
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#else
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struct iovec { void* iov_base; std::size_t iov_len; };
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#endif
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// std::span cannot possibly be layout-compatible with struct iovec because
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// iovec::iov_base is a void* and span<void> is ill-formed. Additionally,
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// the libstdc++ std::span uses [[no_unique_address]] on the second member,
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// so that it's not present for a span of static extent, and that affects
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// layout-compatibility too.
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// Use this to check the size and alignment are compatible.
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template<typename T, typename U>
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constexpr bool same_size_and_alignment
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= std::is_standard_layout_v<T> && std::is_standard_layout_v<U>
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&& sizeof(T) == sizeof(U) && alignof(T) == alignof(U);
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void
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test_pr95609()
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{
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using rbuf = std::span<const std::byte>;
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static_assert(same_size_and_alignment<rbuf, struct iovec>);
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using wbuf = std::span<std::byte>;
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static_assert(same_size_and_alignment<wbuf, struct iovec>);
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}
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