[XALANJ-2030] Relational expression yields wrong result for right-hand param operand

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 2.6
• Fix Version/s: 2.7
• Component/s: XSLTC
• Assignee: Unassigned
• Reporter: Alfred Nathaniel
• Created: 23/Dec/04 11:28
• Updated: 20/Dec/07 16:03
• Resolved: 28/Oct/05 18:38

Description

The bug can be demonstrated with the following stylesheet:

<?xml version="1.0"?>
<!-- bug1.xsl -->
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">

<xsl:param name="six" select="/input/@six"/>

<xsl:template match="/">
<result>
<xsl:if test="5 < $six">
okay 5 lt $six
</xsl:if>
<xsl:if test="7 < $six">
fail 7 lt $six
</xsl:if>
<xsl:if test="$six > 5">
okay $six gt 5
</xsl:if>
<xsl:if test="$six > 7">
fail $six gt 7
</xsl:if>
</result>
</xsl:template>
</xsl:stylesheet>

Given the input:

<?xml version="1.0"?>
<!-- in1.xml -->
<input six="6"/>

The correct result produced by the Xalan interpreter is:

xalan -in in1.xml -xsl bug1.xsl
<result>
okay 5 lt $six
okay $six gt 5
</result>

XSLTC 2.6.0 produces a wrong result where 7 < $six evaluates as true:

xalan -in in1.xml -xsl bug1.xsl -xsltc -v
>>>>>>> Xalan Version Xalan Java 2.6.0, <<<<<<<
<result>
fail 7 lt $six
okay $six gt 5
</result>

The bug is introduced because for simplifying the comparison the operands are swapped without adapting non-commuting operators accordingly. Here is the patch to be applied in org/apache/xalan/xsltc/runtime/BasisLibrary.java:

— BasisLibrary.java.orig 2004-02-27 20:45:28.000000000 +0100
+++ BasisLibrary.java 2004-12-21 10:48:29.644000000 +0100
@@ -741,8 +741,16 @@

if (hasSimpleType(left) ||
left instanceof DOM && right instanceof DTMAxisIterator)

{ - // swap operands + // swap operands and conjugate non-commuting operator final Object temp = right; right = left; left = temp; + if (op == GT) + op = LE; + else if (op == LT) + op = GE; + else if (op == GE) + op = LT; + else if (op == LE) + op = GT; }

if (left instanceof DOM) {

This particular bug manifests itself only under very specific circumstances. It only occurs if a node-set is passed as parameter (<xsl:param> or <xsl:with-param>) and used as right-hand-side operator in a relational expression.

If one is aware of it's presence, it can be avoid be any of these variations:

*) Use variable instead of parameter:
<xsl:variable name="six" select="/input/@six"/>
*) Explicit conversion to number in assignment:
<xsl:param name="six" select="number(/input/@six)"/>
*) Explicit conversion to number in expression:
<xsl:if test="7 < number($six)">
*) Move parameter to left-hand-side:
<xsl:if test="$six >= 7">

PS What I didn't understand is the difference between xsl:param and xsl:variable. Why does Param.typeCheck cast _select from node-set to reference?

Issue Links

• duplicates: XALANJ-2003 XSLTC tail recursion outputs backwards