bug#36431: Crash in marker.c:337

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: wl@gnu.org,  36431@debbugs.gnu.org
> Date: Sun, 30 Jun 2019 10:59:09 -0400
> 
> > More generally, I'd be leery to make significant changes ion
> > insert-file-contents just to placate that single assertion.
> 
> I'm still trying to really understand what the code is doing, but so far
> I get the impression that there are real bugs there, so I'm not really
> concerned with resolving the assertion but with fixing those bugs.
> Of course, to do that, I first need to understand the code (which maybe
> will convince me that there aren't any bugs after all).

I'm not sure those are bugs.  When we manipulate the gap, the buffer
is left in inconsistent state for short periods of time, and that is
normal AFAIU.