| 1 | //===----------------------------------------------------------------------===// |
|---|
| 2 | // |
|---|
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
|---|
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
|---|
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
|---|
| 6 | // |
|---|
| 7 | //===----------------------------------------------------------------------===// |
|---|
| 8 | |
|---|
| 9 | // UNSUPPORTED: c++03, c++11, c++14, c++17 |
|---|
| 10 | |
|---|
| 11 | // <bit> |
|---|
| 12 | // |
|---|
| 13 | // template<class To, class From> |
|---|
| 14 | // constexpr To bit_cast(const From& from) noexcept; // C++20 |
|---|
| 15 | |
|---|
| 16 | // This test makes sure that std::bit_cast fails when any of the following |
|---|
| 17 | // constraints are violated: |
|---|
| 18 | // |
|---|
| 19 | // (1.1) sizeof(To) == sizeof(From) is true; |
|---|
| 20 | // (1.2) is_trivially_copyable_v<To> is true; |
|---|
| 21 | // (1.3) is_trivially_copyable_v<From> is true. |
|---|
| 22 | // |
|---|
| 23 | // Also check that it's ill-formed when the return type would be |
|---|
| 24 | // ill-formed, even though that is not explicitly mentioned in the |
|---|
| 25 | // specification (but it can be inferred from the synopsis). |
|---|
| 26 | |
|---|
| 27 | #include <bit> |
|---|
| 28 | #include <concepts> |
|---|
| 29 | |
|---|
| 30 | template<class To, class From> |
|---|
| 31 | concept bit_cast_is_valid = requires(From from) { |
|---|
| 32 | { std::bit_cast<To>(from) } -> std::same_as<To>; |
|---|
| 33 | }; |
|---|
| 34 | |
|---|
| 35 | // Types are not the same size |
|---|
| 36 | namespace ns1 { |
|---|
| 37 | struct To { char a; }; |
|---|
| 38 | struct From { char a; char b; }; |
|---|
| 39 | static_assert(!bit_cast_is_valid<To, From>); |
|---|
| 40 | static_assert(!bit_cast_is_valid<From&, From>); |
|---|
| 41 | } |
|---|
| 42 | |
|---|
| 43 | // To is not trivially copyable |
|---|
| 44 | namespace ns2 { |
|---|
| 45 | struct To { char a; To(To const&); }; |
|---|
| 46 | struct From { char a; }; |
|---|
| 47 | static_assert(!bit_cast_is_valid<To, From>); |
|---|
| 48 | } |
|---|
| 49 | |
|---|
| 50 | // From is not trivially copyable |
|---|
| 51 | namespace ns3 { |
|---|
| 52 | struct To { char a; }; |
|---|
| 53 | struct From { char a; From(From const&); }; |
|---|
| 54 | static_assert(!bit_cast_is_valid<To, From>); |
|---|
| 55 | } |
|---|
| 56 | |
|---|
| 57 | // The return type is ill-formed |
|---|
| 58 | namespace ns4 { |
|---|
| 59 | struct From { char a; char b; }; |
|---|
| 60 | static_assert(!bit_cast_is_valid<char[2], From>); |
|---|
| 61 | static_assert(!bit_cast_is_valid<int(), From>); |
|---|
| 62 | } |
|---|
| 63 | |
|---|
