[Sablevm-developer] types of stack frames

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

Hi Etienne (and possibly David or Greg, but not sure),

Can you please write about the types of stack frames / methods that 
might be on the stack in SableVM, and when they are pushed and popped? 
For one, I would like to know about pushing and popping native methods.

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, or whether I have to 
go in and increment a counter on every push and keep track of pops 
explicitly (which gets a little complicated because of exceptions).

I would like to do this so that I can make some basic assertions about 
post-execution system properties of programs running with spmt.  I'll 
take whatever you write and incorporate it into David's 
"stack_layout.txt" document.

Thanks very much,
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)
     {
       if (_svmf_is_set_flag (method->access_flags, SVM_ACC_INTERNAL)
           == JNI_FALSE &&
           _svmf_is_set_flag (method->access_flags, SVM_ACC_NATIVE)
           == JNI_FALSE)
         {
           count++;
         }
       frame = (_svmt_stack_frame *)
         (((char *) frame) - frame->previous_offset);
       method = frame->method;
     }
   return count;
}