[PATCH] PR libstdc++/80316 make promise::set_value throw no_state error

[Jonathan Wakely]

On 4 April 2017 at 20:44, Jonathan Wakely wrote:
> We got a bug report from a customer pointing out that calling
> promise::set_value on a moved-from promise crashes instead of throwing
> an exception with error code future_errc::no_state.
>
> This fixes it, by moving the _S_check calls to *before* we deference
> the pointer that the calls check!
>
> This passes all tests, including the more comprehensive ones I've
> added as part of this commit, but I think it can wait for stage 1
> anyway. We've been shipping this bug for a couple of releases already.
>
>         PR libstdc++/80316
>         * include/std/future (_State_baseV2::_Setter::operator()): Remove
>         _S_check calls that are done after the pointer to the shared state
> is
>         already dereferenced.
>         (_State_baseV2::_Setter<_Res, void>): Define specialization for void
>         as partial specialization so it can be defined within the definition
>         of _State_baseV2.
>         (_State_baseV2::__setter): Call _S_check.
>         (_State_baseV2::__setter(promise<void>*)): Add overload for use by
>         promise<void>::set_value and
> promise<void>::set_value_at_thread_exit.
>         (promise<T>, promise<T&>, promise<void>): Make _State a friend.
>         (_State_baseV2::_Setter<void, void>): Remove explicit
> specialization.
>         (promise<void>::set_value, promise<void>::set_value_at_thread_exit):
>         Use new __setter overload.
>         * testsuite/30_threads/promise/members/at_thread_exit2.cc: New test.
>         * testsuite/30_threads/promise/members/set_exception.cc: Test
>         promise<T&> and promise<void> specializations.
>         * testsuite/30_threads/promise/members/set_exception2.cc: Likewise.
>         Test for no_state error condition.
>         * testsuite/30_threads/promise/members/set_value2.cc: Likewise.


This is now committed to trunk.