Re: XEmacs segfault

Ralf Angeli <[email protected]> writes:

> * David Kastrup (2005-02-01) writes:
>
>> Ralf Angeli <[email protected]> writes:
>>
>>> When trying to prepare an example for the xemacs-beta list XEmacs just
>>> died.  I am currently on a dial-up connection and won't search for the
>>> reference to the respective message including a backtrace but you
>>> should be able to find it via Gmane.
>>>
>>> I suspect the segfault is a result of the presence of shy groups in
>>> `LaTeX-auto-class-regexp-list'.  At least it doesn't happen if I
>>> remove the entries containing shy groups from the variable.  We
>>> should definitely not ship 11.55 with these regexps enabled in
>>> XEmacs.
>>
>> !@##@$#!
>
> Yes, it's really getting funny.
>
>> What XEmacs version?
>
> 21.4.16.  There was some discussion on the XEmacs lists about problems
> with shy groups in connection with Gnus.  In this case the result was
> a hang of XEmacs.  As far as I know this started with 21.4.16.  They
> recently found a fix for that but I don't know if this will fix as
> well the segfault I am seeing here.
>
> It wouldn't be a big deal to disable the regexps in concern for XEmacs
> in general, but if we get some feedback from the XEmacs people we
> could probably disable them for affected releases only.
>
>> We _do_ have some do-not-use-shy-regexp comment in preview.el.
>
> For XEmacs in general?

2002-04-04  Nix  <[email protected]>

	* preview.el (preview-parse-messages):
	Cater for XEmacs shy grouping bug (shy grouping
	very nearly doesn't work in XEmacs-21.4...)

2002-03-15  David Kastrup  <[email protected]>

	(preview-parse-messages): New regexp parser.  Nick, if the shy
	groups \(?: ...\) worry XEmacs, make them non-shy and adjust the
	match-... thingies appropriately.
	(preview-analyze-error): and another save-restriction...

However, the actual code at least now uses quite a few shy regexps.
But fewer than the comments if I can see correctly.  So it would
appear that either only _some_ usage of shy regexps was tragic at that
time, or that in the mean time, without XEmacs users complaining
violently, preview-latex has become non-operative.  I doubt that the
latter is really the case.

The problem with Nix at that time (our XEmacs porter) is that he was
working in whirlwind mode and his first priority was to get things
running without having to touch too many things.  So it is unclear
what of the stuff for which he introduced bandaid fixes and
workarounds actually got fixed in XEmacs.  He _did_ quite a bit of
work fixing things also in XEmacs, but there were also things he did
not touch IIRC.

More details will probably be found in the archives of the
preview-latex-devel list which is not available through gmane at that
point of time, I think, but via sourceforge.

But I don't recollect that Nix actually fixed anything WRT regexps,
and not having followed the XEmacs lists, I don't know what and how he
reported problems.

The way it sounds from the ChangeLog, it appears to be some
"well-known" problem at the time.  But maybe I am mistaken.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum