1 //===----------------------------------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 // <mutex>
11 
12 // struct once_flag;
13 
14 // constexpr once_flag() noexcept;
15 
16 #include <mutex>
17 
main()18 int main()
19 {
20     {
21     std::once_flag f;
22     }
23 #ifndef _LIBCPP_HAS_NO_CONSTEXPR
24     {
25     constexpr std::once_flag f;
26     }
27 #endif
28 }
29