Re: [Sablevm-developer] types of stack frames

[Chris P. <chr...@ma...>]

Chris Pickett wrote:

> I wrote a simple function to count Java stack frames, but it gives me 
> more frames than those that are pushed directly with (PREPARE_)INVOKE<X> 
> (as calculated by a more indirect method).  I assume it's because some 
> Java frames are pushed without (PREPARE_)INVOKE<X>.  I would really like 
> to know if it's possible to count frames pushed only with 
> (PREPARE_)INVOKE<X> by simply looking at the stack

It seems that I can do this if I don't count any frame that has a 
non-"pushed by (PREPARE_)INVOKE<X>" frame below it.  The code following 
almost works, but appears to be off-by-one.  If you can spot an obvious 
error I'd be grateful, otherwise I'll just keep digging (into source and 
specifications).

Cheers,
Chris

inline static size_t
_svmf_count_java_stack_frames (_svmt_JNIEnv *env)

{
   _svmt_stack_frame *frame = env->stack.current_frame;
   _svmt_method_info *method = frame->method;

   jint count = 0;

   while (method != &env->vm->stack_bottom_method)
     {

       jboolean found_java_frame = JNI_FALSE;

       /* is the current frame internal? */
       if (_svmf_is_set_flag (method->access_flags, SVM_ACC_INTERNAL)
	  == JNI_FALSE)
         {
           found_java_frame = JNI_TRUE;
         }

       /* pop stack frame */
       frame = (_svmt_stack_frame *)
         (((char *) frame) - frame->previous_offset);
       method = frame->method;

       /* if the previous frame was not internal and this one
           is not internal, increment the count of
           pushed-by-java frames
        */
       if (_svmf_is_set_flag (method->access_flags, SVM_ACC_INTERNAL)
           == JNI_FALSE &&
           found_java_frame == JNI_TRUE)
         {
           count++;
         }
     }
   return count;
}