https://issues.apache.org/bugzilla/show_bug.cgi?id=45230
Summary: tableswitch/lookupswitch invalid alignment of 4-byte
operands
Product: BCEL
Version: 5.2
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P2
Component: Main
AssignedTo: bcel-dev@jakarta.apache.org
ReportedBy: talper@coverity.com
Created an attachment (id=22137)
--> (https://issues.apache.org/bugzilla/attachment.cgi?id=22137)
Testcase: sample application that reproduces the bug
It is possible, with BCEL, to generate invalid alignment of the 4-byte operands
of the Select instructions. The problem is caused by the interaction of
InstructionList.setPositions, the updatePosition methods of GOTO and JSR, and
Select.updatePosition.
In particular, the updatePosition methods of GOTO and JSR will always return
the difference between the wide instruction length and the normal instruction
length. Since this value ends up being added into the additional_bytes variable
in InstructionList.setPositions and then eventually contributes to the value
passed into Select.updatePosition as the offset, its incorrect value causes the
padding field to be set incorrectly.
It appears that in order to behave properly, the updatePosition method should
return only the number of bytes of length that the instruction changed during
this call to updatePosition.
I am attaching a small example application that displays the bug.
I will also be attaching a patch.
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