task: co_return with_error(...) & with_stopped - #2154
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The standard specifies that std::execution::task shall destroy the coroutine frame before sending set_stopped to the receiver in the case of unhandled_stopped: The asynchronous operation is completed by first destroying the coroutine frame [...] and then invoking set_stopped(std::move( st.rcvr)). STDEXEC::task previously belied this, instead destroying the coroutine frame sometime after the dispatch of set_stopped. Added a reproducing unit test and corrected.
The standard specifies that co_yield with_error(e) is valid if e is convertible to one of the task's error types: Mandates: std::move(err.error) is convertible to exactly one of the set_error_t argument types of error_types. STDEXEC::task previously belied this instead requiring that e be exactly one of the error types (rather than convertible to exactly one such type). Fixed and added a reproducing unit test.
ericniebler
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Aug 2, 2026
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/ok to test fdf37b8 |
Implemented P4282 by enhancing task as follows: - co_yield can now be used directly to send set_stopped using the new with_stopped tag - co_return can now be used with with_error and with_stopped to send set_error or set_stopped, respectively Note that the co_return functionality requires a compiler which implements P3950 (adopted into the C++29 working draft in Brno) when used with a task<void>.
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Two bugfixes and implementation of of P4282R1 Away From
co_yieldForstd::execution::task.Note that newly-added
co_returnfunctionality fortask<void>requires a compiler which provides P3950R1return_value&return_voidAre Not Mutually Exclusive.