Mark Roberts created BCEL-283:
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Summary: Support for StackMap should be different from
StackMapTable
Key: BCEL-283
URL: https://issues.apache.org/jira/browse/BCEL-283
Project: Commons BCEL
Issue Type: Bug
Reporter: Mark Roberts
It turns out we made a mistake with the StackMap renaming changes. I ran into
a problem decoding some old .class files and went back to the Java
Specification Requests (JSRs) to try and understand the history of the StackMap
attribute. While I was not able to get the complete story, I have a pretty
good guess at what happened and it does explain the problem I have seen.
The official introduction of StackMaps appears to be JSR 202 from (approx.)
Sept. 2006 and it is part of JDK6 (see attached spec) . However, StackMaps
were originally proposed much earlier (approx.) March 2002 - see the attached
verifier spec. It appears there were some implementations of this earlier
specification - the ASM tool was one and there may be others.
The key differences are:
Typechecker Spec: StackMap attribute with fixed format and no frame type
byte
JDK 6 Spec: StackMapTable attribute with variable format including
a frame type byte.
The JVM and the javap tool support BOTH formats. BCEL recognizes both
attribute names, but treats them the same, as JDK6 version.
I don't think the changes will be too difficult. I will create a proposed fix
within the next few days.
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