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Private non-static method can not debug and get "this" field #111

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924060929 opened this issue Feb 15, 2020 · 1 comment
Open

Private non-static method can not debug and get "this" field #111

924060929 opened this issue Feb 15, 2020 · 1 comment

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@924060929
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the code is

class MyTest {
  private int value = 10;
  private void test() {
    System.out.println(value);
  }
}

When I generate the code by Janino and copy the code to a file MyTest.java,and step into the test function,I can't look the variable this and value in Intellij IDEA.

Then I debug the Janino 3.0.0,and find the logical in UnitCompiler#compile(FunctionDeclarator, ClassFile) is change the private non-static method to package static method, and add the "this" to the method's first argument.

"This" in IDEA is this object, but in Janino is the first augument, this cause the problem.

Can U support this debug function :)

@aunkrig
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aunkrig commented Feb 26, 2020

Hey Mrs. or Mr. Anonymous,

modeling non-static private methods with static default-accessible methods is a trick of JANINO:

    if (fd.getAccess() == Access.PRIVATE) {
        if (fd instanceof MethodDeclarator && !((MethodDeclarator) fd).isStatic()) {

            // To make the non-static private method invocable for enclosing types, enclosed types and types
            // enclosed by the same type, it is modified as follows:
            //  + Access is changed from PRIVATE to PACKAGE
            //  + The name is appended with "$"
            //  + It is made static
            //  + A parameter of type "declaring class" is prepended to the signature
            short accessFlags = UnitCompiler.changeAccessibility(this.accessFlags(fd.getModifiers()), Mod.PACKAGE);
            accessFlags |= Mod.STATIC;

            mi = classFile.addMethodInfo(
                accessFlags,   // accessFlags
                fd.name + '$', // methodName
                (              // methodMd
                    this.toIMethod((MethodDeclarator) fd)
                    .getDescriptor()
                    .prependParameter(this.resolve(fd.getDeclaringType()).getDescriptor())
                )
            );

It is not enough to change accessibility from PRIVATE to PACKAGE, because PRIVATE-accessible methods are non-virtual, and PACKAGE-accessible methods are not.

Sorry it breaks IDEA!

The idea behind this is to avoid those ridiculous "access$000()" methods that Java generates to make private methods accessible for enclosing and enclosed classes. A very questionable concept anyway, because it pollutes the generated classes, the call stacks, and also adds security vulnerabilities.

But I see your point and will think of a way to get around this problem. Stay tuned.

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