DO NOT REPLY [Bug 43732] New: - Error in method search() defined in org.apache.bcel.util.InstructionFinder

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http://issues.apache.org/bugzilla/show_bug.cgi?id=43732

           Summary: Error in method search() defined in
                    org.apache.bcel.util.InstructionFinder
           Product: BCEL
           Version: 5.2
          Platform: Other
        OS/Version: Windows XP
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Main
        AssignedTo: [email protected]
        ReportedBy: [email protected]


While Peephole.java is a small program in the manual to remove “NOP”
instructions in any class file, it uses the method search() defined in
org.apache.bcel.util.InstructionFinder with string pattern ‘NOP+’ to locate the
“NOP” instructions in the instructionList. After several tests, I found the
search() method will always find one more instruction after the expected
instructions, what’s more, it will raise a
java.lang.ArrayIndexOutOfBoundsException if the expected instruction is at the
end of the method.

After reading the source-code of org.apache.bcel.util.InstructionFinder, I found
there is something wrong when we calculate the length of the match[] array.

In the codes of how to get the match[] array. The startExpr is the first index
of the ”NOP” instruction, and the endExpr is the first index of the non-NOP
instruction. So the real length of the match[] should be endExpr-startExpr. But
we use endExpr-startExpr+1 as the length of the array. So instead of getting the
expected match[] array, we’ll get an one-instruction-longer match[] in the
instructionList incorrectly.

As a result, I guess if the statement “int lenExpr = (endExpr - startExpr) + 1;”
should be replaced by “int lenExpr =endExpr - startExpr;”.

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