Fix LWG Issue 2078. Make std::async(policy,...) try multiple policies until one succeeds.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@193960 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/future b/include/future
index ff8e59b..7561d19 100644
--- a/include/future
+++ b/include/future
@@ -2331,20 +2331,32 @@
}
};
+bool __does_policy_contain(launch __policy, launch __value )
+{ return (int(__policy) & int(__value)) != 0; }
+
template <class _Fp, class... _Args>
future<typename __invoke_of<typename decay<_Fp>::type, typename decay<_Args>::type...>::type>
async(launch __policy, _Fp&& __f, _Args&&... __args)
{
typedef __async_func<typename decay<_Fp>::type, typename decay<_Args>::type...> _BF;
typedef typename _BF::_Rp _Rp;
- future<_Rp> __r;
- if (int(__policy) & int(launch::async))
- __r = _VSTD::__make_async_assoc_state<_Rp>(_BF(__decay_copy(_VSTD::forward<_Fp>(__f)),
+
+#ifndef _LIBCPP_NO_EXCEPTIONS
+ try
+ {
+#endif
+ if (__does_policy_contain(__policy, launch::async))
+ return _VSTD::__make_async_assoc_state<_Rp>(_BF(__decay_copy(_VSTD::forward<_Fp>(__f)),
__decay_copy(_VSTD::forward<_Args>(__args))...));
- else if (int(__policy) & int(launch::deferred))
- __r = _VSTD::__make_deferred_assoc_state<_Rp>(_BF(__decay_copy(_VSTD::forward<_Fp>(__f)),
+#ifndef _LIBCPP_NO_EXCEPTIONS
+ }
+ catch ( ... ) { if (__policy == launch::async) throw ; }
+#endif
+
+ if (__does_policy_contain(__policy, launch::deferred))
+ return _VSTD::__make_deferred_assoc_state<_Rp>(_BF(__decay_copy(_VSTD::forward<_Fp>(__f)),
__decay_copy(_VSTD::forward<_Args>(__args))...));
- return __r;
+ return future<_Rp>{};
}
template <class _Fp, class... _Args>