bug#25362: 26.0.50; comment-region goes into an infinite loop

[Eli Zaretskii]

> Date: Sat, 7 Jan 2017 08:20:23 +0000
> Cc: dima@secretsauce.net, 25362@debbugs.gnu.org
> From: Alan Mackenzie <acm@muc.de>
> 
> There are actually two distinct bugs at work, here.  One of them is
> simple, the fix being merely giving a limit to an invocation of
> c-forward-syntactic-ws.

Does doing that prevent the infloop?

> The other bug is more involved.  It involves the invalidation of the
> whitespace cache, which is currently done incorrectly when "//" is
> inserted into a line which already has comment markers later on that
> line.  It should be simple to fix, but is actually quite tricky, with a
> likelihood of unwanted side effects if it's not done very carefully.  I
> might be able to fix it today, but I'm not certain of that.
> 
> I've done a bisection on the repository, and the commit that
> "introduced" the bug didn't really introduce it at all - it merely
> uncovered it.  That commit was 4b9ac23960d2998f899287ffcf696ad33b63a69a
> from 2016-07-03, "Speed up CC Mode fontification with less accurate
> functions extending region".

If no better solution emerges, would it make sense to revert 4b9ac23
on the release branch, as a temporary workaround that prevents the
infloop?

Thanks.