[jboss-jira] [JBoss JIRA] Closed: (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=all ]

Yanic Inghelbrecht closed JASSIST-52.
-------------------------------------

    Resolution: Done

no longer an issue, see explanation above.

> 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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