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