63 lines
1.9 KiB
C++
63 lines
1.9 KiB
C++
//===----------------------------------------------------------------------===//
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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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// UNSUPPORTED: c++03, c++11, c++14, c++17
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// <bit>
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//
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// template<class To, class From>
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// constexpr To bit_cast(const From& from) noexcept; // C++20
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// This test makes sure that std::bit_cast fails when any of the following
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// constraints are violated:
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//
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// (1.1) sizeof(To) == sizeof(From) is true;
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// (1.2) is_trivially_copyable_v<To> is true;
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// (1.3) is_trivially_copyable_v<From> is true.
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//
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// Also check that it's ill-formed when the return type would be
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// ill-formed, even though that is not explicitly mentioned in the
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// specification (but it can be inferred from the synopsis).
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#include <bit>
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#include <concepts>
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template<class To, class From>
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concept bit_cast_is_valid = requires(From from) {
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{ std::bit_cast<To>(from) } -> std::same_as<To>;
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};
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// Types are not the same size
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namespace ns1 {
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struct To { char a; };
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struct From { char a; char b; };
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static_assert(!bit_cast_is_valid<To, From>);
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static_assert(!bit_cast_is_valid<From&, From>);
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}
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// To is not trivially copyable
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namespace ns2 {
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struct To { char a; To(To const&); };
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struct From { char a; };
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static_assert(!bit_cast_is_valid<To, From>);
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}
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// From is not trivially copyable
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namespace ns3 {
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struct To { char a; };
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struct From { char a; From(From const&); };
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static_assert(!bit_cast_is_valid<To, From>);
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}
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// The return type is ill-formed
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namespace ns4 {
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struct From { char a; char b; };
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static_assert(!bit_cast_is_valid<char[2], From>);
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static_assert(!bit_cast_is_valid<int(), From>);
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}
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