bug#47024: 28.0.50; [feature/native-comp] Warnings from async compilations truncated

[Eli Zaretskii]

> From: Andrea Corallo <akrl@sdf.org>
> Cc: 47024@debbugs.gnu.org
> Date: Wed, 10 Mar 2021 06:50:15 +0000
> 
> > The message comes from a sub-process, right?
> 
> Yes
> 
> > Could it be that we
> > match prematurely, when only part of the text was received?
> 
> That's possible, just before using the regexp we call
> `accept-process-output' on the process, I thought this was sufficient to
> handle the case but I'm no expert into this area.

I think I see the problem: it's nothing as complicated as that.

Here's what the original warning looks like:

 seq.el:396:16: Warning: `seq-contains' is an obsolete generic function (as of
     27.1); use `seq-contains-p' instead.

There's an actual newline at the end of the first line, because by
default we _fill_ the text.

So I think the solution should be to bind (in the sub-process which
performs the actual compilation) warning-fill-column to a large
number.

Is there a similar issue with error messages?