bug#59038: loading this base64 file makes emacs -Q 28.2 peg a core infinitely

[Gregory Heytings]

> > > This is reproducible with master 
> > > fd3f51b7c3a6649ee3db12d33b056b1afdbfa7e9.
> >
> > What is reproducible, exactly?  Visiting the file is almost 
> > instantaneous here, in Emacs 29.
>
> Visiting the file, yes.  Try C-e, and you'll see that Emacs hangs.  At 
> least it does, here.

Another recipe:
emacs -Q
M-: (set-frame-width nil 100)
C-x C-f Looper.h RET

Note that this bug has nothing to do with long lines.  That file opens 
just fine in other modes (e.g. Fundamental, Elisp, Text), even with long 
line optimizations turned off.