libcxx/test/std/thread/futures/futures.async/async.verify.cpp

   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: no-threads
  10 // UNSUPPORTED: c++03, c++11, c++14, c++17
  11
  12 // <future>
  13
  14 // template <class F, class... Args>
  15 //     future<typename result_of<F(Args...)>::type>
  16 //     async(F&& f, Args&&... args);
  17
  18 // template <class F, class... Args>
  19 //     future<typename result_of<F(Args...)>::type>
  20 //     async(launch policy, F&& f, Args&&... args);
  21
  22
  23 #include <future>
  24
  25 int foo (int x) { return x; }
  26
  27 void f() {
  28     std::async(                    foo, 3); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
  29     std::async(std::launch::async, foo, 3); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
  30 }