ASM (from ObjectWeb) not calculating MaxStack correctly even though ClassWriter( COMPUTE_MAX + COMPUTE_STACK ) is set

I am getting expected ClassVerifyErrors when attempting to load a class i have generated using ASM. On further inspection i can see that the jvm is correct and that the method is talking about has an invalid MAX_STACK value. THe stra开发者_JS百科nge thing is am using the auto calculate the stack and max local options so this should not be a problem... The method with the invalid option is very simple and yet the result is bad bytecode.

I have written a class with the intended method and compared my asm generated class against what javac produces and the byte codes matchup with the only error being the max stack is 0 which is wrong while javac sets a value of 2.

Id like to avoid having to calculate tha max stack/locals myself.

Max stack and variable calculation can produce the wrong results if bytecode is not valid. You can verify that by running generated code trough the CheckClassAdapter.

For example,

  ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
  // generate code into cw instance...

  PrintWriter pw = new PrintWriter(System.out);
  CheckClassAdapter.verify(new ClassReader(cw.toByteArray()), true, pw);