Re: Capy: Request for endorsements

Hello,

After digging deeper in corosio's code base from the following link:
https://github.com/cppalliance/corosio/blob/0cb2c0096ca2cf8f7c1f1617cb04c19120dd4f12/include/boost/corosio/tcp_server.hpp#L500
You were spot-on with my suggestions, keeping the Executor concept as is would indeed be beneficial per P4007 [2] (Sender and Co-routines, https://wg21.link/p4007)

Thanks,
Amlal.

On 2/20/26 15:11, Vinnie Falco via Boost wrote:
> On Fri, Feb 20, 2026 at 4:32 AM Amlal El Mahrouss via Boost <
> [email protected]> wrote:
>
>> I also have a question about the following snippet at:
>> https://github.com/cppalliance/capy/blob/develop/example/asio/use_capy_example.cpp#L118C70-L119C1
>>
>> We can see at line 119:
>>
>> ```cpp
>> capy::run_async(ctx.get_executor())(run_example(client, server));
>> ```
>>
>> It's elegant, but maybe we could also benefit from this syntax as well:
>>
>> ```cpp
>> auto& exec{ctx.get_executor()};
>> exec.run_async(run_example(client, server));
>> ```
>>
> So, if I understand you correctly then you are asking for the Executor
> concept to have additional members:
>
>      unspecified run_async( IoRunnable auto&& );
>
> This is problematic for a few reasons explained P4003[1]
>
> 1.  An Executor is a low-level primitive. It only specifies how a coroutine
> is resumed. A launch function is something different: a high level
> construct responsible for creating the environment in which a coroutine
> runs, and specifying behavior when the coroutine performs its final
> suspend. run_async falls in the latter category.
>
> 2. The one-call syntax you propose suffers from the allocator timing
> problem described in P4007 Senders and Coroutines [2]. The coroutine frame
> would be created before the allocator has the chance to propagate.
>
> 3. `run_async` is just one example of a launch function: a function which
> begins a new coroutine chain of execution either from a regular function
> (such as main) or a coroutine. The set of launch functions is open, as
> users can (and will) define their own. Here is one such example:
>
> https://github.com/cppalliance/corosio/blob/0cb2c0096ca2cf8f7c1f1617cb04c19120dd4f12/include/boost/corosio/tcp_server.hpp#L500
>
> It makes sense to keep the Executor concept as a low-level narrow
> abstraction, and partition the launch functions into a higher level
> algorithmic set.
>
> Thanks
>
> [1] https://wg21.link/p4003 IoAwaitables: A Coroutines-Only Framework
>
> [2] https://wg21.link/p4007 Senders and Coroutines
>
> P.S. I suppose its pointless asking for the copyright discussion to be
> moved to a separate thread :)
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