Re: [capy] error codes

On Wednesday, July 1st, 2026 at 12:49 AM, Andrzej Krzemienski via Boost <[email protected]> wrote:

> Functions pull_from and push_to special-case on cond::eof. So do a number
> of examples in the docs. Why only this one? I have been told that
> cond::stream_truncated means "end of file, transmission ended before the
> handshake, may be a truncation attack, may be a safe  end, judge yourself."

The pumps treats eof specially because it is the only situation in which we can finalize the sink (commit_eof). On the stream version you get success, on the sink versions if commit succeeds you get success or the ec from committing. This seems consistent.

> How can users make this call when some Capy functions already discard it?

Where does Capy discard it? It should bubble up through ec.

> BTW, looking at the implementation of pull_from and push_to, when an error
> is reported, there is no way to figure out from which stream it originated.

I think you're right about this and we should fix it.

> Looking at the implementation in normalize_openssl_shutdown_read_error in
> Corosio, it looks like when we decide to stop a task reading an SSL stream
> we will not get cond::canceled, but instead we may get
> cond::stream_truncated. This is the only place where -- against the
> protocol -- we do not get the feedback that the operation was canceled as
> requested.

Yes, I think the mapping to stream_truncated is too aggressive. It should be addressed as well.

> BTW, cond::canceled detects two things: a successfully processed
> cancellation request (error::canceled) and other events, possibly caused by
> the state of the socket at the other end.(std::errc::operation_canceled).
> It is not a practical condition.

cond::canceled should answer "was this canceled?," that seems like the correct usage of cond. If you want to know specifics you could check against specific error codes.
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