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Posted to dev@xalan.apache.org by "Henry Zongaro (JIRA)" <xa...@xml.apache.org> on 2005/06/15 16:49:47 UTC
[jira] Updated: (XALANJ-2146) Byte code generated by XSLTC contains backwards branch when uninitialized object is on stack
[ http://issues.apache.org/jira/browse/XALANJ-2146?page=all ]
Henry Zongaro updated XALANJ-2146:
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Description:
Section 4.3.4 of the Java Virtual Machine Specification, 2nd Edition, places the following restriction on Java byte code:
«A valid instruction sequence must not have an uninitialized object on the operand stack or in a local variable during a backwards branch, or in a local variable in code protected by an exception handler or a finally clause. Otherwise, a devious piece of code might fool the verifier into thinking it had initialized a class instance when it had, in fact, initialized a class instance created in a previous pass through a loop.»
There are a number of places where XSLTC generates code that violates this requirement; a strict implementation of the verification process described by the JVM specification would detect the invalid byte code. Most popular JVMs do not seem to detect this problem - presumably because their verification is less stringent - but this is a problem that needs to be fixed.
See copy16.xsl for an example of the offending code sequence. The id function seems to be involved in all cases that pose a problem.
was:
Section 4.3.4 of the Java Virtual Machine Specification, 2nd Edition, places the following restriction on Java byte code:
«A valid instruction sequence must not have an uninitialized object on the operand stack or in a local variable during a backwards branch, or in a local variable in code protected by an exception handler or a finally clause. Otherwise, a devious piece of code might fool the verifier into thinking it had initialized a class instance when it had, in fact, initialized a class instance created in a previous pass through a loop.»
There are a number of places where XSLTC generates code that violates this requirement; a strict implementation of the verification process described by the JVM specification would detect the invalid byte code. Most popular JVMs do not seem to detect this problem - presumably because their verification is less stringent - but this is a problem that needs to be fixed.
> Byte code generated by XSLTC contains backwards branch when uninitialized object is on stack
> --------------------------------------------------------------------------------------------
>
> Key: XALANJ-2146
> URL: http://issues.apache.org/jira/browse/XALANJ-2146
> Project: XalanJ2
> Type: Bug
> Components: XSLTC
> Versions: CurrentCVS
> Reporter: Henry Zongaro
> Assignee: Henry Zongaro
> Priority: Critical
> Fix For: 2.7.0-future-release
>
> Section 4.3.4 of the Java Virtual Machine Specification, 2nd Edition, places the following restriction on Java byte code:
> «A valid instruction sequence must not have an uninitialized object on the operand stack or in a local variable during a backwards branch, or in a local variable in code protected by an exception handler or a finally clause. Otherwise, a devious piece of code might fool the verifier into thinking it had initialized a class instance when it had, in fact, initialized a class instance created in a previous pass through a loop.»
> There are a number of places where XSLTC generates code that violates this requirement; a strict implementation of the verification process described by the JVM specification would detect the invalid byte code. Most popular JVMs do not seem to detect this problem - presumably because their verification is less stringent - but this is a problem that needs to be fixed.
> See copy16.xsl for an example of the offending code sequence. The id function seems to be involved in all cases that pose a problem.
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