Re: [xsl] XSL and infinite loops

Subject: Re: [xsl] XSL and infinite loops
From: David Carlisle <davidc@xxxxxxxxx>
Date: Thu, 26 Aug 2004 18:07:28 +0100
> Thanks! I'm having trouble picturing a scenario in which for-each --
> by itself -- could cause an infinite loop under XSLT 1.0/XPath
> 1.0. Did you have a specific case in mind? 

Not really, in fact for some definitions of "by itself" then it provably
doesn't loop as all node sets are finite and it just iterates over that
finite set.

I think what I had in mind is that it can be used to avoid certain
simple minded restrictions that you may put on apply-templates to avoud

apply-templates will only directly cause looping if it is used with a
reverse axis (including self:: axis)
apply-templates select="."

so if you are trying to avoid DOS attacks you could try to restrict the
select attribute so it only uses Xpaths that select descendent children

but then a for-each with select="/" would get you back up the tree with a
potential for looping again.

in a stylesheet that just has:


<xsl:template match="*">
<xsl:for-each select="/">


you will loop but whether you say it is the apply-templates or the
for-each that causes the looping is a matter of taste, if you take
either of them out it doesn't loop any more.


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