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: libcpp-has-no-threads
10 // UNSUPPORTED: c++98, c++03, c++11
11 
12 // <shared_mutex>
13 
14 // template <class Mutex> class shared_lock;
15 
16 // mutex_type* release() noexcept;
17 
18 #include <shared_mutex>
19 #include <cassert>
20 
21 struct mutex
22 {
23     static int lock_count;
24     static int unlock_count;
25     void lock_shared() {++lock_count;}
26     void unlock_shared() {++unlock_count;}
27 };
28 
29 int mutex::lock_count = 0;
30 int mutex::unlock_count = 0;
31 
32 mutex m;
33 
34 int main(int, char**)
35 {
36     std::shared_lock<mutex> lk(m);
37     assert(lk.mutex() == &m);
38     assert(lk.owns_lock() == true);
39     assert(mutex::lock_count == 1);
40     assert(mutex::unlock_count == 0);
41     assert(lk.release() == &m);
42     assert(lk.mutex() == nullptr);
43     assert(lk.owns_lock() == false);
44     assert(mutex::lock_count == 1);
45     assert(mutex::unlock_count == 0);
46     static_assert(noexcept(lk.release()), "release must be noexcept");
47 
48   return 0;
49 }
50