Re: [xsl] XSL and infinite loops

[David Carlisle <davidc@xxxxxxxxx>]

> 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
looping.

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:stylesheet...>

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

</xsl:stylesheet>

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.



David

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