bug#68272: [PATCH] Fix -1 leaking from C to lisp in 'read-event' etc.

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: crypto@timruffing.de,  68272@debbugs.gnu.org
> Date: Tue, 05 Mar 2024 12:57:56 -0500
> 
> >> > IOW, what about callers that actually _want_ to know when the macro
> >> > ends prematurely?
> >> I couldn't find any, really.
> > ??? calc is one, obviously.
> 
> I don't think so: AFAICT the tests there were added simply
> because they had to do something with this -1 return value.

Any evidence?  Andreas thought differently, what if he is right?