[jboss-jira] [JBoss JIRA] Commented: (JASSIST-51) Editing a NewExpr results in a VerifyError (inconsistent stack height)

[Yanic Inghelbrecht (JIRA)]

    [ http://jira.jboss.com/jira/browse/JASSIST-51?page=comments#action_12402112 ] 
            
Yanic Inghelbrecht commented on JASSIST-51:
-------------------------------------------

Splendid, thanks for such a quick fix!

> Editing a NewExpr results in a VerifyError (inconsistent stack height)
> ----------------------------------------------------------------------
>
>                 Key: JASSIST-51
>                 URL: http://jira.jboss.com/jira/browse/JASSIST-51
>             Project: Javassist
>          Issue Type: Bug
>         Environment: Javassist 3.7, JDK 1.6.0_03 on WinXP
>            Reporter: Yanic Inghelbrecht
>         Assigned To: Shigeru Chiba
>
> The code below is the simplest case I could find that reproduces the error. The code contains two classes : Client and Main. Client is the class that gets instrumented, Main does the instrumenting. The error that result is :
> Exception in thread "main" java.lang.VerifyError: (class: test_try_catch/Client, method: instrumentMe signature: ()V) Inconsistent stack height 0 != 1
> 	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_try_catch.Main.main(Main.java:30)
> Javassist somehow messes up on instrumenting the NewExpr in method Client#instrumentMe
> The weird thing about this bug is, the verifyError only occurs when the method containing the NewExpr also contains a try/catch block! 
> For me this is a show stopper, not using  try/catch blocks is not really an option :o)
> I hope you agree this is a high priority issue, because our project cannot be released because of this.
> Best regards,
> Yanic
> --------- source code for Client.java below
> package test_try_catch;
> import java.util.ArrayList;
> public class Client {
> 	public void instrumentMe() {
> 		// we need a 'new' expression to instrument, the exact type is not important
> 		new Object();
> 		
> 		// if the try/catch block below is removed, the error does not occur
> 		try {
> 			System.out.println();
> 		} catch (Throwable t) {
> 			//
> 		}
> 	}
> }
> --------- source code for Main.java below
> package test_try_catch;
> 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.NewExpr;
> 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_try_catch.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(NewExpr m) throws CannotCompileException {
> 			// no changes, for simplicity's sake
> 			String block = "{$_=$proceed($$);}";
> 			m.replace(block);
> 		}
> 		public void start(ClassPool pool) throws NotFoundException, CannotCompileException {
> 			// do nothing
> 		}
> 	}	
> }

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