[Soot-list] Unnecessary instructions in generated bytecode

[Matteo Ceccarello]

Hi all,

I am using this code to write class files:

|FileNameGenerator.mkDirsForClass(cls, baseDir);
String fileName ="filename";
OutputStream streamOut =new  JasminOutputStream(new  FileOutputStream(fileName));
PrintWriter writerOut =new  PrintWriter(new  OutputStreamWriter(streamOut));

JasminClass jasminClass =new  JasminClass(cls);
jasminClass.print(writerOut);
writerOut.flush();
streamOut.close();|

Then I decompile the bytecode I obtain with different decompilers. 
However I get confused results with almost all of them. This is strange, 
since I do not modify the class with Soot once I load it and decompiling 
the original class file works just fine.

Looking into the generated bytecode I found out that Soot introduces a 
couple of instructions that are not present in the original class: some 
|store|s and |load|s.

Just to make an example, this is the original bytecode of 
|java.lang.Integer.toHexString| method (printed by javap)

|public static java.lang.String toHexString(int);
     Code:
        0: iload_0
        1: iconst_4
        2: invokestatic  #5     // Method toUnsignedString:(II)Ljava/lang/String;
        5: areturn|

The bytecode that Soot outputs is the following:

|public static java.lang.String toHexString(int);
     Code:
        0: iload_0
        1: iconst_4
        2: invokestatic  #49   // Method toUnsignedString:(II)Ljava/lang/String;
        5: astore_0
        6: aload_0
        7: areturn|

As you can see there are two instructions more than the original.

Is this a bug? Should I report it to the github issues page?

In the meantime, since this is a problem for me, is there a way to get 
the Jasmin bytecode representation in order to remove these instructions?

Cheers
Matteo

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