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// <type_traits>
12
13// constexpr bool is_constant_evaluated() noexcept; // C++20
14
15#include <type_traits>
16#include <cassert>
17
18#include "test_macros.h"
19
20#ifndef __cpp_lib_is_constant_evaluated
21#if TEST_HAS_BUILTIN(__builtin_is_constant_evaluated)
22# error __cpp_lib_is_constant_evaluated should be defined
23#endif
24#endif
25
26// Disable the tautological constant evaluation warnings for this test,
27// because it's explicitly testing those cases.
28TEST_CLANG_DIAGNOSTIC_IGNORED("-Wconstant-evaluated")
29TEST_MSVC_DIAGNOSTIC_IGNORED(5063)
30
31template <bool> struct InTemplate {};
32
33int main(int, char**)
34{
35 // Test the signature
36 {
37 ASSERT_SAME_TYPE(decltype(std::is_constant_evaluated()), bool);
38 ASSERT_NOEXCEPT(std::is_constant_evaluated());
39 constexpr bool p = std::is_constant_evaluated();
40 assert(p);
41 }
42 // Test the return value of the builtin for basic sanity only. It's the
43 // compiler's job to test the builtin for correctness.
44 {
45 static_assert(std::is_constant_evaluated(), "");
46 bool p = std::is_constant_evaluated();
47 assert(!p);
48 ASSERT_SAME_TYPE(InTemplate<std::is_constant_evaluated()>, InTemplate<true>);
49 static int local_static = std::is_constant_evaluated() ? 42 : -1;
50 assert(local_static == 42);
51 }
52 return 0;
53}
54

source code of libcxx/test/std/utilities/meta/meta.const.eval/is_constant_evaluated.pass.cpp