InstructionSequencesReplacer - stack map frames

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1

I’m using proguard.classfile.editor.InstructionSequencesReplacer in proguard-core to replace sets of instructions (as shown here). If a stack map frame appears in the middle of an instruction set in a class file, the instruction set is not replaced. Is there a way to have the instructions be replaced?

2

Hi @Askew6226 !

Have you tried running the CodePreverifier after making your changes to recreate the stackmap frames? e.g.

            programClassPool.classesAccept(
                new ClassVersionFilter(VersionConstants.CLASS_VERSION_1_6,
                new AllMethodVisitor(
                new AllAttributeVisitor(
                        new CodePreverifier(false)))));

If this doesn’t help, can you share a reproducible sample?

Thanks,

James

3

Hi @james,

I think the problem I am running into is how I’m trying to handle the stack map frames that appear in the class before I try to replace instructions (though I did try running the CodePreverifier).

I’ve attached a class that contains a stack map frame.

Also attached is what I’m using to make replacements in the class with proguard-core 9.0.8.

I’m using Krakatau to examine the bytecode and I notice that even if I remove the stack map frames, the instruction replacement does not work when I try to replace the “sipush 1122” instruction that comes after the frame.

Am I doing anything wrong?

ClassWithStackMapFrame.java (278 Bytes)

ClassTransformer.java (5.7 KB)

ClassWithStackMapFrame krakatau output:

.version 52 0
.class public super ClassWithStackMapFrame
.super java/lang/Object

.method protected <init> : ()V
    .code stack 4 locals 8
L0:     aload_0
L1:     invokespecial Method java/lang/Object <init> ()V
L4:     invokestatic Method java/lang/System currentTimeMillis ()J
L7:     ldc2_w 55567L
L10:    lsub
L11:    lstore_1
L12:    lload_1
L13:    ldc2_w 12345L
L16:    lsub
L17:    lstore_3
L18:    lload_3
L19:    ldc2_w 567L
L22:    lcmp
L23:    ifne L32
L26:    sipush 890
L29:    goto L35

        .stack full
            locals Object ClassWithStackMapFrame Long Long
            stack
        .end stack
L32:    sipush 1122

        .stack stack_1 Integer
L35:    istore 5
L37:    invokestatic Method java/lang/System currentTimeMillis ()J
L40:    ldc2_w 44455L
L43:    ladd
L44:    lstore 6
L46:    return
L47:
        .linenumbertable
            L0 2
            L4 3
            L12 4
            L18 5
            L37 6
            L46 7
        .end linenumbertable
    .end code
.end method
.sourcefile 'ClassWithStackMapFrame.java'
.end class