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.
28 TEST_CLANG_DIAGNOSTIC_IGNORED("-Wconstant-evaluated")
29 TEST_MSVC_DIAGNOSTIC_IGNORED(5063)
30 
31 template <bool> struct InTemplate {};
32 
33 int 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