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

[Yanic Inghelbrecht (JIRA)]

    [ http://jira.jboss.com/jira/browse/JASSIST-52?page=comments#action_12407656 ] 
            
Yanic Inghelbrecht commented on JASSIST-52:
-------------------------------------------

Hi Chiba,

Have you been able to reproduce this bug with the compiled classes I provided?

Since our project cannot continue using javassist as long as this bug remains, I'm wondering if you have any idea whether or not this can be fixed in the short term. Please let me know so I can make an informed decision about what to do with our project.

Thanks.

> 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
>         Attachments: supplement_to_jassist-52.zip
>
>
> 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
> 		}
> 	}
> }

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