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POASM bytecode instrumentation for method entry / exit
 

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    <p>I've created a JVMTI agent that does the following at a high level:</p> <ul> <li><p>onClassLoadHook send the bytecodes for the loaded class to a separate Java process that will instrument the class using ASM</p></li> <li><p>get the bytecodes back and load them</p></li> </ul> <p>In my seperate java process that instruments the loaded Java class I do the following :</p> <p>.. ..</p> <pre><code> cr = new ClassReader(inBytes, offset, inLen); cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES); ClassAdapter ca = new ClassAdapter(cw) { .. .. @Override public MethodVisitor visitMethod(final int access, final String name, final String desc, String signature, String[] exceptions) { return new MethodAdapter(mv) { @Override public void visitCode() { mv.visitVarInsn(Opcodes.ALOAD, 0); mv.visitMethodInsn(Opcodes.INVOKESTATIC, "com/amir/Tester", "callTestStatic3", "(Ljava/lang/Object;)V"); mv.visitCode(); } } } </code></pre> <p>When I try to decompile the class that is written after this instrumentation using Java Decompiler - I see the following decompiled function which I know is wrong :</p> <pre><code> public void func1(int arg1, int arg2) { int b; Tester.callTestStatic3(???); System.out.println("arg = " + a + " b = " + b); } </code></pre> <p>because my function actually looks like this :</p> <pre><code>public void func1(int a, int b) { System.out.println("arg = " +a + " b = " +b); } </code></pre> <p>Can anyone tell me if I did something wrong here? My only clue is that if instead of passing in as an argument to my function the THIS pointer, if I pass in primitive types, everything works out finie. Is there something special about the THIS pointer that I need to manage? I've compared the bytecodes, and I've used ASMIFIER to get a clue as to what statements I need to use to generate the right bytecodes.</p>
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