https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69724
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:bb1b7f087bdd028000fd8f84e74b20adccc9d5bb commit r11-2736-gbb1b7f087bdd028000fd8f84e74b20adccc9d5bb Author: Jonathan Wakely <jwak...@redhat.com> Date: Tue Aug 18 14:23:19 2020 +0100 libstdc++: Remove redundant copying of std::async arguments [PR 69724] As was previously done for std::thread, this removes an unnecessary copy of an rvalue of type thread::_Invoker. Instead of creating the rvalue and then moving that into the shared state, the member of the shared state is initialized directly from the forwarded callable and bound arguments. This also slightly simplifies std::thread creation to remove the _S_make_state helper function. libstdc++-v3/ChangeLog: PR libstdc++/69724 * include/std/future (__future_base::_S_make_deferred_state) (__future_base::_S_make_async_state): Remove. (__future_base::_Deferred_state): Change constructor to accept a parameter pack of arguments and forward them to the call wrapper. (__future_base::_Async_state_impl): Likewise. Replace lambda expression with a named member function. (async): Construct state object directly from the arguments, instead of using thread::__make_invoker, _S_make_deferred_state and _S_make_async_state. Move shared state into the returned future. * include/std/thread (thread::_Call_wrapper): New alias template for use by constructor and std::async. (thread::thread(Callable&&, Args&&...)): Create state object directly instead of using _S_make_state. (thread::__make_invoker, thread::__decayed_tuple) (thread::_S_make_state): Remove. * testsuite/30_threads/async/69724.cc: New test.
