[jboss-jira] [JBoss JIRA] (JASSIST-210) MethodCall.replace() throws inconsistent stack height in certain scenarios

[Patson Luk (JIRA)]

Patson Luk created JASSIST-210:
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             Summary: MethodCall.replace() throws inconsistent stack height in certain scenarios
                 Key: JASSIST-210
                 URL: https://issues.jboss.org/browse/JASSIST-210
             Project: Javassist
          Issue Type: Bug
            Reporter: Patson Luk
            Assignee: Shigeru Chiba


Tested on 3.16.1-GA

This is similar to https://issues.jboss.org/browse/JASSIST-52, but the try-catch block usage is different (not wrapping the $proceed($$))

Based on the javassist tutorial,  the substituted code for MethodCall.replace():
{{Note that the substituted code is not an expression but a statement or a block. It cannot be or contain a try-catch statement.}}

However in the case that try-catch does not wrap the $_=$proceed($$);
It seems to work properly. For example:

ctClass.instrument(new ExprEditor() {
    public void edit(MethodCall m) throws CannotCompileException {
        if (m.getMethodName().equals("testMethod2")) {
            String newBlock = "{ try { System.out.println(\"injected\"); } catch (Exception e) { e.printStackTrace(); } $_ = $proceed($$); }";
            m.replace(newBlock);
        }
    }
});

{{which ctClass is class TestReplace, which has code as below:}}

public class TestReplace {
    public static void main(String[] args) {
        RefClass ref = new RefClass();
        ref.testMethod2();
    }
}

class RefClass {
    public void testMethod1(Object o) {}
    public Object testMethod2() { return null; }
}

{{running TestReplace with the modified bytecode correctly prints "injected" to the screen. However if I add one more line to the TestReplace's main() method}}

ref.testMethod1(ref.testMethod2());

{{It throws exception as below}}
javassist.bytecode.BadBytecode: inconsistent stack height -1
javassist.bytecode.stackmap.Tracer.doOpcode(Tracer.java:106)

*So is try-catch acceptable if it does not wrap the $_=$proceed($$)? If so, is it a bug if it does not work properly for method invocation within another method invocation?*

Many thanks in advance!


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