Verifier error with try-finally clause in Java 1.7 --------------------------------------------------- Key: JASSIST-195 URL: https://issues.jboss.org/browse/JASSIST-195 Project: Javassist Issue Type: Bug Affects Versions: 3.17.1-GA Environment: Oracle Java 1.7 on Mac OS X Reporter: John Brush Assignee: Shigeru Chiba Fix For: 3.18.0-GA After upgrading from Java 1.6 to Java 1.7 our unit tests failed due to the new verifier in 1.7 which requires a stack map. I fixed this issue by adding a call to the rebuildStackMap() method after instrumentation, but this caused a new problem to pop up in one particular instance: {code} public int testInstrumentedCallInFinallyBlock( int i ) { try {} catch ( Throwable t ) {} finally { i = incByOne( i ); } return i; } {code} This unit test results in the following exception: java.lang.VerifyError: Stack map does not match the one at exception handler 9 in method xxx.StatementsTestComponent.testInstrumentedCallInFinallyBlock(I)I at offset 9 After some investigation, I noticed that the problem occurred independent of my instrumentation, simply as a result of loading the byte code with Javassist, invoking rebuildStackMap() and then trying to load it. The byte code for the above snippet looks as follows before invoking rebuildStackMap(): {code} Code: stack=2, locals=3, args_size=2 0: aload_0 1: iload_1 2: invokespecial #3 // Method incByOne:(I)I 5: istore_1 6: goto 18 9: astore_2 10: aload_0 11: iload_1 12: invokespecial #3 // Method incByOne:(I)I 15: istore_1 16: aload_2 17: athrow 18: iload_1 19: ireturn Exception table: from to target type 9 10 9 any StackMapTable: number_of_entries = 2 frame_type = 73 /* same_locals_1_stack_item */ stack = [ class java/lang/Throwable ] frame_type = 8 /* same */ {code} Afterwards, it looks like this: {code} Code: stack=2, locals=3, args_size=2 0: aload_0 1: iload_1 2: invokespecial #23 // Method incByOne:(I)I 5: istore_1 6: goto 18 9: nop 10: nop 11: nop 12: nop 13: nop 14: nop 15: goto 9 18: iload_1 19: ireturn Exception table: from to target type 9 10 9 any StackMapTable: number_of_entries = 2 frame_type = 249 /* chop */ offset_delta = 9 frame_type = 253 /* append */ offset_delta = 8 locals = [ class ch/shaktipat/saraswati/instrument/busicomp/StatementsTestComponent, int ] {code} Notice the modifications from lines 9-15: this is a result of Javassist's MapMaker.fixDeadcode() method. I assume that the verify error is a result of the exception table entry that refers to code which is no longer there. A possible fix would be to make sure that any exception handlers referring to dead code are removed in such cases. Personally, I would prefer that Javassist simply not modify the code if at all possible, or at least for such modifications to be optional (configurable). BTW: my only workaround for the time being is to force the 1.7 JVM to use the old verifier with -XX:-UseSplitVerifier.