Re: [xslt] small patch for xsltFreeStylePreComps()

[Daniel Veillard <veillard redhat com>]

On Tue, May 02, 2006 at 07:54:14PM -0700, Aleksey Sanin wrote:
> Hello, All!
> 
> I run into a small problem with re-using XSLT stylesheet document
> in the following scenario (the same xmlDocPtr is used for more
> than one stylesheet):
> 
> 	xmlDocPtr xslt_doc;
> 	xsltStylesheetPtr stylesheet;
> 
> 	xslt_doc = ... ; /* Get xslt doc somehow */
> 	...
> 
> 	/* use doc stylesheet first time */
> 	stylesheet = xsltParseStylesheetDoc(xslt_doc);
> 	out1 = xsltApplyStylesheet(stylesheet, in1);
> 	... /* consume out1 */
> 	xsltFreeStylesheet(stylesheet);
> 	
> 	...
> 
> 	/* use doc stylesheet first time */
> 	stylesheet = xsltParseStylesheetDoc(xslt_doc);
> 	out2 = xsltApplyStylesheet(stylesheet, in2);   <--- crash
> 	... /* consume out2 */
> 	xsltFreeStylesheet(stylesheet);
> 
> 
> I understand that this is probably a corner case scenario since
> it is much better to do not re-create xsltStylesheetPtr second
> time. But at the moment it is not possible to do in my case.
> 
> It turns out that the crash is caused by invalid pointer in
> "psvi" member of xmlNodePtr. The actual data structure was freed
> by the first xsltFreeStylesheet() call but the "psvi" pointer
> was still pointed to it. The attached patch fixes the problem by
> making sure that we cleanup this "psvi" pointer when we destroy
> the data structure.
> 
> I would appreciate if someone can take a look at the patch and
> check that it is not doing something stupid :)

  stylesheet compilation modifies the input doc, a lot ...
The patch may make sense, but you should really reparse the input.
Or find a way to reuse the compiled stylesheet.

> diff -ur libxslt/preproc.c libxslt/preproc.c
> --- libxslt/preproc.c	2005-03-29 05:12:59.000000000 -0800
> +++ libxslt/preproc.c	2006-05-02 19:09:33.682620800 -0700
> @@ -1321,6 +1321,8 @@
>      cur = style->preComps;
>      while (cur != NULL) {
>  	next = cur->next;
> +       if(cur->inst != NULL)
> +           cur->inst->psvi = NULL;
>  	if (cur->type == XSLT_FUNC_EXTENSION)
>  	    cur->free(cur);
>  	else

  I defer to Kasimier for this since he's playing with this at the moment.

Daniel

-- 
Daniel Veillard      | Red Hat http://redhat.com/
veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/