| //===----------------------------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| // UNSUPPORTED: c++03, c++11, c++14, c++17 |
| |
| // <bit> |
| // |
| // template<class To, class From> |
| // constexpr To bit_cast(const From& from) noexcept; // C++20 |
| |
| // This test makes sure that std::bit_cast fails when any of the following |
| // constraints are violated: |
| // |
| // (1.1) sizeof(To) == sizeof(From) is true; |
| // (1.2) is_trivially_copyable_v<To> is true; |
| // (1.3) is_trivially_copyable_v<From> is true. |
| // |
| // Also check that it's ill-formed when the return type would be |
| // ill-formed, even though that is not explicitly mentioned in the |
| // specification (but it can be inferred from the synopsis). |
| |
| #include <bit> |
| #include <concepts> |
| |
| template<class To, class From> |
| concept bit_cast_is_valid = requires(From from) { |
| { std::bit_cast<To>(from) } -> std::same_as<To>; |
| }; |
| |
| // Types are not the same size |
| namespace ns1 { |
| struct To { char a; }; |
| struct From { char a; char b; }; |
| static_assert(!bit_cast_is_valid<To, From>); |
| static_assert(!bit_cast_is_valid<From&, From>); |
| } |
| |
| // To is not trivially copyable |
| namespace ns2 { |
| struct To { char a; To(To const&); }; |
| struct From { char a; }; |
| static_assert(!bit_cast_is_valid<To, From>); |
| } |
| |
| // From is not trivially copyable |
| namespace ns3 { |
| struct To { char a; }; |
| struct From { char a; From(From const&); }; |
| static_assert(!bit_cast_is_valid<To, From>); |
| } |
| |
| // The return type is ill-formed |
| namespace ns4 { |
| struct From { char a; char b; }; |
| static_assert(!bit_cast_is_valid<char[2], From>); |
| static_assert(!bit_cast_is_valid<int(), From>); |
| } |