[Phpwiki-talk] why preg_match crashes sometimes

[Reini U. <ru...@x-...>]

I've come now this analysis why ConvertOldMarkup() crashes with certain 
pages, and why not always. This is the only remaining showstopper for 
the 1.3.11 release, but it's an ugly and persistent one.

Symptoms:
?action=loadfile&source=pgsrc&overwrite=1
crashes sometimes at the second encounter of the anchored regex loop at 
the page "OldTextFormattingRules", esp. if the CreateToc plugin is used.
Similarily some more large old markup pages, but this is the only one 
from the default pgsrc set.

But, loading the single page will work okay:
?action=loadfile&source=pgsrc/OldTextFormattingRules&overwrite=1

It crashes more often on linux, esp on sf.net php-4.1.2 than on newer 
versions, esp Windows seems to be much more stable.
Apache2 and IIS crash more often than Apache1.

Possibly related symptom:
ADODB requires much more memory since the library upgrade with 1.3.10, 
so that AllPages will fail > ~300 pages, without any given limit 
parameter. Playing with the limit parameter will narrow the max. pageset 
size.
But, PearDB will fail also.

Possible Reason:
Somehow the cached database use too much memory when simply iterating 
over get_all_pages(). Exhausting the available php memory will crash 
anchored PCRE matches, which is a (yet unknown) PHP bug.

What I have done so far:
I've tried to improve the sql calls, and to purge the cache from 
unneeded data on such page iterations.
* _cached_html should be kept in the cache for the requested page. This 
new policy is not yet enforced globally, just for some API calls.
* pagedata[%content'] should only be kept for pages which really need 
the content. e.g. for the size column on pagelists the content can be 
safely purged after having done the strlen(). Sorting on size makes it 
problematic.
Nevertheless, despite these efforts the memory footprint increased 
dramatically lately, though it really should have been decreased.
   https://sourceforge.net/forum/message.php?msg_id=2654786

I'm investigating this further. Maybe someone heard about similar 
problems elsewhere.
-- 
Reini Urban
http://phpwiki.sf.net/