Re: [Sablevm-developer] adventures in not understanding the java stack

[Etienne G. <gag...@uq...>]

Chris,

some answers below.

Chris Pickett wrote:
> 2) Do all calls to _svmf_interpreter() end in INTERNAL_CALL_END (it 
> appears this way from invoke_interface.c)?

No.  They can also end:
- at line 636 of interpreter.c: initializing the interpreter.
- at line 400 of interpreter.c: exception path.

> 3) If I keep track of _svmf_interpreter() call depth and Java call 
> depth, abort speculative children on GC or exceptions in the parent 
> non-speculative thread, and abort speculative children on global 
> memory-writing (Java heap or not) instructions in the speculative child, 
> am I correct to assume that the "speculative" stack obtained after 
> jumping over a method call will not differ from the actual stack when 
> that point is reached non-speculatively?

Which stack?  The operand stack, or the Java stack?

Do not forget about _svmf_ensure_stack_capacity() which can actually
change the "absolute" location of the Java stack (and thus the absolute
location of the operand stack).

> 4) Can I furthermore assert that the next instruction to be executed 
> after a method call has completed, in the absence of an exception being 
> thrown in the call, is the next instruction in the code array?

Yes.

> 5) Do calls to _svmf_interpreter() enter and exit cleanly?  In other 
> words, am I right to assume that there is nothing like a Java exception 
> that can occur to screw up control flow, and that when the height of the 
> call stack returns you are back where you started?

_svmf_interpreter sets a longjump handler, so it never exits other than
through "return" (at one of 3 identified locations: 2 above + INTERNAL_CALL_END)
as far as I remember.


-- 
Etienne M. Gagnon, Ph.D.             http://www.info.uqam.ca/~egagnon/
SableVM:                                       http://www.sablevm.org/
SableCC:                                       http://www.sablecc.org/