Asm bytecode queries

Question

Hey all, I am trying to use the ASM bytecode Tree Api to do static analysis for a class. I guess I have a pretty basic question. In a method say foobar(), I have a list of instructions within foobar (InsnList which has a List). Now I want to check if at instruction number 10, whether a function "barfoo(String args)" is being invoked.

Also seperatly, I need to verify whether a particular instruction is a conditional.

Thanks and Regards, SJ

Note: I can already read a class and reach the particular method I am interested in and iterate through each intruction of that method.

Solved (see: Greg's comments):

 AbstractInsnNode s = ... if(s.getType()==AbstractInsnNode.METHOD_INSN){ MethodInsnNode methodInvocationNode = (MethodInsnNode) s; if(methodInvocationNode.name.equals("barfoo")) { return true; } }

thanks Chris.... dint knw we are suppsd to do that.... doing nw — dreamer13134
– dreamer13134, Commented Apr 16, 2011 at 20:47
Do you know what the individual JVM instructions mean? Just trying to figure out where you're starting from here. — Greg Hewgill
– Greg Hewgill, Commented Apr 16, 2011 at 20:47
Then what's the question? Given the instruction at offset 10, you should know how to determine whether the bytecode there is invoking a specific function. Similarly, given a specific instruction it should be trivial to determine whether it's a conditional or not. — Greg Hewgill
– Greg Hewgill, Commented Apr 16, 2011 at 20:57
That's right, invokespecial is one of the bytecodes that can invoke a method (there are a few more). It looks like you'll have to call getType() on your instruction node, and if the type is METHOD_INSN then you can cast to a MethodInsnNode. From there, look at .name to see the method name. — Greg Hewgill
– Greg Hewgill, Commented Apr 16, 2011 at 21:19

Greg Hewgill · Accepted Answer · 2011-04-16 21:50:58Z

From looking at the ASM javadoc, it looks like you'll have to call getType() on your instruction node, and if the type is METHOD_INSN then you can cast to a MethodInsnNode. From there, look at .name to see the method name.

Amir Afghani · Accepted Answer · 2011-04-16 21:00:11Z

Simple - once you've determined that you've invoked foobar, start incrementing a counter on each instruction you visit. On the tenth invocation, perform your check for the invocation of barfoo.

He doesn't need to run the code for the visitors to visit the class/method/instructions.

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