Bug #4045: Null pointer exception when compiling stylesheet with template containing specific XSLT instructions - Saxon - Saxonica Developer Community

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Bug #4045

closed

Null pointer exception when compiling stylesheet with template containing specific XSLT instructions

Added by Philip Fearon about 6 years ago. Updated almost 6 years ago.

Status:

Closed

Priority:

Normal

Assignee:

Michael Kay

Category:

Internals

Sprint/Milestone:

Start date:

2018-11-21

Due date:

% Done:

100%

Estimated time:

Legacy ID:

Applies to branch:

9.9

Fix Committed on Branch:

9.9

Fixed in Maintenance Release:

9.9.1.1

Platforms:

Description

Using Saxon 9.9.0.2 professional (java), the attached saxon9902issue.xsl stylesheet fails to compile, producing the following stack trace. With Saxon 9.9.0.1, no exception is thrown.

java.lang.NullPointerException
	at net.sf.saxon.expr.Expression.getRetainedStaticContext(Expression.java:461)
	at net.sf.saxon.expr.parser.LoopLifter.process(LoopLifter.java:50)
	at net.sf.saxon.expr.parser.ExpressionTool.optimizeComponentBody(ExpressionTool.java:1216)
	at net.sf.saxon.style.XSLTemplate.optimize(XSLTemplate.java:1054)
	at net.sf.saxon.style.PrincipalStylesheetModule.optimizeTopLevel(PrincipalStylesheetModule.java:1446)
	at net.sf.saxon.style.PrincipalStylesheetModule.compile(PrincipalStylesheetModule.java:1267)
	at net.sf.saxon.style.Compilation.compilePackage(Compilation.java:329)
	at net.sf.saxon.style.StylesheetModule.loadStylesheet(StylesheetModule.java:258)
	at net.sf.saxon.style.Compilation.compileSingletonPackage(Compilation.java:107)
	at net.sf.saxon.s9api.XsltCompiler.compile(XsltCompiler.java:778)
	at net.sf.saxon.Transform.doTransform(Transform.java:730)
	at net.sf.saxon.Transform.main(Transform.java:80)
Fatal error during transformation: java.lang.NullPointerException:  (no message)

This issue can be reproduced using both the command-line interface or the Java API

Files

saxon9902issue.xsl (1006 Bytes) saxon9902issue.xsl

Philip Fearon, 2018-11-21 14:05

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Updated by Michael Kay about 6 years ago

Category set to Internals
Status changed from New to Resolved
Assignee set to Michael Kay
Priority changed from Low to Normal
Fix Committed on Branch 9.9 added

Thanks for reporting it.

As a workaround, you can change the template whose body is <xsl:copy/> to <xsl:copy-of select="."/> (it's Saxon's attempt to do this rewrite that is the immediate cause of the trouble.)

Saxon uses a bit of a belt-and-braces approach to ensuring that the expression tree remains consistent, in particular that static context and location information is always retained across tree rewrites. In this case both the belt and the braces failed. (a) we had to copy the template body because it applies to more than one mode, (b) the instruction being copied is rewritten during the typechecking phase, (c) the CopyOf instruction, when copied, doesn't explicitly copy across the location information, (c) the ContextItemExpression created by Copy.typeCheck() isn't given any location information. Fixing either (c) or (d) would solve the problem and I have fixed both.

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