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Add [[nodiscard]] to std::async as part of P0600.

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git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@318889 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Marshall Clow
2017-11-23 01:25:03 +00:00
parent 18a2685809
commit 70c7bbd04f
3 changed files with 40 additions and 2 deletions
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3
include/future
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@@ -2335,6 +2335,7 @@ inline _LIBCPP_INLINE_VISIBILITY bool __does_policy_contain(launch __policy, lau
{ return (int(__policy) & int(__value)) != 0; }
template <class _Fp, class... _Args>
_LIBCPP_NODISCARD_AFTER_CXX17
future<typename __invoke_of<typename decay<_Fp>::type, typename decay<_Args>::type...>::type>
async(launch __policy, _Fp&& __f, _Args&&... __args)
{
@@ -2360,7 +2361,7 @@ async(launch __policy, _Fp&& __f, _Args&&... __args)
}
template <class _Fp, class... _Args>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
future<typename __invoke_of<typename decay<_Fp>::type, typename decay<_Args>::type...>::type>
async(_Fp&& __f, _Args&&... __args)
{

2
include/new
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@@ -271,7 +271,7 @@ template <class _Tp>
_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
constexpr _Tp* launder(_Tp* __p) noexcept
{
return __launder(__p);
return _VSTD::__launder(__p);
}
#endif

37
test/std/thread/futures/futures.async/async.fail.cpp Normal file
View File

@@ -0,0 +1,37 @@
//===----------------------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// UNSUPPORTED: libcpp-has-no-threads
// UNSUPPORTED: c++98, c++03
// <future>
// template <class F, class... Args>
// future<typename result_of<F(Args...)>::type>
// async(F&& f, Args&&... args);
// template <class F, class... Args>
// future<typename result_of<F(Args...)>::type>
// async(launch policy, F&& f, Args&&... args);
#include <future>
#include <atomic>
#include <memory>
#include <cassert>
#include "test_macros.h"
int foo (int x) { return x; }
int main ()
{
std::async( foo, 3); // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
std::async(std::launch::async, foo, 3); // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
}