Code restructure failed on small program

ambergorzynski commented 2 months ago

Issue details

I am using jadx to decompile class files that were originally written in textual bytecode using Jasmin. I am aware that this is an atypical use case and so may be out of scope for jadx! The original method is relatively simple to restructure by hand so I am opening an issue in case it is of interest:

.method public testCase([I[I)V
    .limit stack 5
    .limit locals 6

block_0:
    iconst_0
    istore_3

    sipush 0

    ifeq block_2
    goto block_1

block_1: 
    sipush 1

    ifeq block_1
    goto block_2

block_2: 
    iinc 3 1
    return

.end method

However jadx fails to decompile and warns that code restructuring fails:

package defpackage;

/* compiled from: program.j */
/* loaded from: TestCase.class */
public class TestCase {
    /* JADX WARN: Code restructure failed: missing block: B:2:0x0005, code lost:

        if (0 != 0) goto L5;
     */
    /* JADX WARN: Code restructure failed: missing block: B:3:0x0014, code lost:

        r9 = 0 + 1;
     */
    /* JADX WARN: Code restructure failed: missing block: B:4:0x001a, code lost:

        return;
     */
    /* JADX WARN: Code restructure failed: missing block: B:7:0x000e, code lost:

        if (1 == 0) goto L11;
     */
    /*
        Code decompiled incorrectly, please refer to instructions dump.
        To view partially-correct add '--show-bad-code' argument
    */
    public void testCase(int[] r7, int[] r8) {
        /*
            r6 = this;
            r0 = 0
            r9 = r0
            r0 = 0
            if (r0 == 0) goto L14
            goto Lb
        Lb:
            r0 = 1
            if (r0 == 0) goto Lb
            goto L14
        L14:
            int r9 = r9 + 1
            return
        */
        throw new UnsupportedOperationException("Method not decompiled: defpackage.TestCase.testCase(int[], int[]):void");
    }
}

Relevant log output or stacktrace

No response

Provide sample and class/method full name

I attach a .zip file with the following:

program.j which is the original bytecode progam
TestCase.class which is the class file associated with program.j
TestCase.java which is the output of applying JadX to TestCase.class

example.zip

Jadx version

1.5.0

skylot commented 2 months ago

Fixed. @ambergorzynski thanks for test case, although it is way too synthetic, now jadx outputs

    public void testCase(int[] iArr, int[] iArr2) {
        if (0 != 0) {
            while (1 == 0) {
            }
        }
        int i = 0 + 1;
    }

and it still not compilable because of "unreachable statement" :rofl: Compilable and meaningful cases are preferred :slightly_smiling_face:

BTW, if you're still using Jasmin, it will be nice if you also look at my raung project, any feedback is welcome.

ambergorzynski commented 2 months ago

Thanks! Understood on the compilable and meaningful case preference :grin:

And thanks for pointing me to raung, looks very cool! I will check it out.

skylot / jadx