stack map frames

Hi,

I don't know if this is the right place to ask question. If not, I would
like to hear that from you. In the meantime I just ask my question.

I have tried to do in ASM

        void g(long d){
        try{
                Thread.sleep(d);
        }catch(InterruptedException e){
                e.printStackTrace()     ;
        }
        }

I did

ClassWriter w=new ClassWriter(ClassWriter.COMPUTE_FRAMES)       ;
...
MethodVisitor v6=w.visitMethod(ACC_PUBLIC,"g","(J)V",null,null) ;
v6.visitCode()  ;
Label t=new Label()     ;
Label c=new Label()     ;
Label f=new Label()     ;
v6.visitTryCatchBlock(t,c,c,"java/lang/InterruptedException")   ;
v6.visitLabel(t)        ;
v6.visitVarInsn(LLOAD,1);
v6.visitMethodInsn(INVOKESTATIC, "java/lang/Thread", "sleep", "(J)V");
v6.visitJumpInsn(GOTO,f);
v6.visitLabel(c)        ;
v6.visitVarInsn(ASTORE,3);
v6.visitVarInsn(ALOAD,3);
v6.visitMethodInsn(INVOKEVIRTUAL, "java/lang/InterruptedException",
"printStackTrace", "()V");
v6.visitLabel(f)        ;
v6.visitInsn(RETURN);
v6.visitMaxs(0,0);
v6.visitEnd();

With javap on the result I see

  public void g(long);
    Signature: (J)V
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=4, args_size=2
         0: lload_1
         1: invokestatic  #23     // Method java/lang/Thread.sleep:(J)V
         4: goto          12
         7: astore_3
         8: aload_3
         9: invokevirtual #26  // Method
java/lang/InterruptedException.printStackTrace:()V
        12: return
      Exception table:
         from    to  target type
             0     7     7   Class java/lang/InterruptedException
      StackMapTable: number_of_entries = 2
           frame_type = 71 /* same_locals_1_stack_item */
          stack = [ class java/lang/InterruptedException ]
           frame_type = 4 /* same */

When I compile the Java code and look at javap on that, I see almost the
same, but in the exception table it says 'to 4' instead of 'to 7'.

I have studied jdk1.2.2, so stack map frames are new for me. They are not in
my JVM spec book. Do you know a place where they are explained, so I can
read about them? So that I can understand 'frame type = 71'       .

Also did I programmed it right in ASM, because of the difference in the
exception table?

Also suppose I do
        ClassWriter w=new ClassWriter(0)
Which MethodVisitor.visitFrame calls I have to make, and where?

I hope it is not too much. Thanks.

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