bug#36492: c-mode fails with errors during fontification

[Alan Mackenzie <acm@muc.de>]

Hello, Juri.

On Mon, Jul 08, 2019 at 00:52:02 +0300, Juri Linkov wrote:
> >>> Opening this message in Gnus fails with the following backtrace
> >>> because c-mode fails to fontify the attachment.

> >> Actually, with the attachment in this message the bug in c-mode
> >> font-lock is much easier to reproduce.

> > That is one ugly piece of erroneous C.  ;-)

> > What triggers the bug is the ) without a preceding (.  A variable
> > recording the position of the opening ( is still set to nil, and we
> > tried to use it in the given buffer with the unbalanced ).

> >> [-- text/x-csrc, encoding 7bit, charset: US-ASCII, 3 lines, name: test.c --]

> > The following patch fixes it, I hope.  Would you please do the usual,
> > and confirm that it does indeed fix the bug (or tell me what's still
> > wrong).

> Thanks, Alan.  Now there is no error anymore.

Thanks.  I've committed the fix, and I'm closing the bug.

> I wonder if ignore-errors around font-lock-ensure in mm-display-inline-fontify
> is still necessary to ensure no more bugs in other modes disrupt Gnus
> by erroneous code in attachments?  Or maybe raising such errors will help
> to find fontification bugs sooner?

My feeling is that it's better to let the errors happen, so that we can
debug them.  But on the other hand, it's not me that gets inconvenienced
by such an error (I don't use gnus).

-- 
Alan Mackenzie (Nuremberg, Germany).