[jboss-jira] [JBoss JIRA] Created: (JASSIST-52) VerifyError (inconsistent stack height) through MethodCall#replace when block includes a try/catch block

[Yanic Inghelbrecht (JIRA)]

VerifyError (inconsistent stack height) through MethodCall#replace when block includes a try/catch block
--------------------------------------------------------------------------------------------------------

                 Key: JASSIST-52
                 URL: http://jira.jboss.com/jira/browse/JASSIST-52
             Project: Javassist
          Issue Type: Bug
         Environment: javassist 3.7.1 (from cvs HEAD), jdk 1.6.0_03 on winXP
            Reporter: Yanic Inghelbrecht
         Assigned To: Shigeru Chiba


Included is the simplest test case I could find that reproduces the error, it consists of two classes : Client (to be instrumented) and Main (does the instrumentation).

When run, it produces the following exception trace :

Exception in thread "main" java.lang.VerifyError: (class: test_verify_error_with_try_catch_in_replace/Client, method: instrumentMe signature: ()V) Inconsistent stack height 0 != 2
	at java.lang.Class.getDeclaredConstructors0(Native Method)
	at java.lang.Class.privateGetDeclaredConstructors(Unknown Source)
	at java.lang.Class.getConstructor0(Unknown Source)
	at java.lang.Class.newInstance0(Unknown Source)
	at java.lang.Class.newInstance(Unknown Source)
	at test_verify_error_with_try_catch_in_replace.Main.main(Main.java:30)

The error disappears  in all of the following cases (so it must be related to them I guess) :
 - when the try/catch block is removed from the replacement block
 - when the string concatenation happens without using two local variables
 - when the string concatenation is removed but the local variables are kept

This is related (for me at least) to JIRA JAVASSIST 51, where a similar error occurred for NewExpr (and was quickly fixed, thanks again for that!!). 

Just like issue 51, it is a show stopper for our project since it all ties in with the support for exceptions in the development tool we're creating, so I hope you will again regard it as an urgent issue.

Thanks in advance.

Best regards,
Yanic

-- source code for client.java

package test_verify_error_with_try_catch_in_replace;

public class Client {
	public void instrumentMe() throws Exception {
		// the error is somehow related to the string concatenation and local variables,
		// when the code below is replaced with something else, the error does not occur.
		String s1 = "a";
		String s2 = s1 + "b";
	}
}

-- source code for Main.java

package test_verify_error_with_try_catch_in_replace;
import java.lang.reflect.Method;

import javassist.CannotCompileException;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;
import javassist.Loader;
import javassist.NotFoundException;
import javassist.Translator;
import javassist.expr.ExprEditor;
import javassist.expr.MethodCall;


public class Main {
	public static void main(String[] args) throws Exception {
		ClassPool pool = new ClassPool(true);
		Loader cl = new Loader();
		try {
			cl.addTranslator(pool, new MyTranslator());
		} catch (Exception e) {
			e.printStackTrace();
			return;
		}
		
		// load the Client class
		Class clientClass=cl.loadClass("test_verify_error_with_try_catch_in_replace.Client");
		
		// create an instance
		Object client=clientClass.newInstance();
		
		// execute Client#instrumentMe
		Method callMethod=clientClass.getMethod("instrumentMe", new Class[]{});
		callMethod.invoke(client, new Object[]{});
	}
	
	static public class MyTranslator extends ExprEditor implements Translator {

		public void onLoad(ClassPool pool, String classname) throws NotFoundException, CannotCompileException {
			CtClass cc = pool.get(classname);
			modify(cc);
		}

		public void modify(CtClass c) throws CannotCompileException {
			for (CtMethod m : c.getMethods()) {
				m.instrument(this);
			}
		}

		@Override
		public void edit(MethodCall mc) throws CannotCompileException {
			// simple proceed surrounded by a try/catch block
			String block = "{try{$_=$proceed($$);} catch(Throwable t) {}}";
			mc.replace(block);
		}

		public void start(ClassPool pool) throws NotFoundException, CannotCompileException {
			// do nothing
		}
	}
}

-- 
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators: http://jira.jboss.com/jira/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira