[m-dev.] for review: fix for stack traces in -O-1

[Mark Anthony BROWN]

> 
> Hi,
> 
> Mark, want to review this one?

Sure.

...
> Index: library/require.m
> ===================================================================

...

> +:- pragma c_code("
> +
> +Define_extern_entry(mercury__require__error_internal_1_0);
> +
> +MR_MAKE_STACK_LAYOUT_ENTRY(mercury__require__error_internal_1_0);
> +
> +BEGIN_MODULE(require_module_internal)
> +        init_entry(mercury__require__error_internal_1_0);
> +BEGIN_CODE
> +
> +/* code for predicate 'error'/1 in mode 0 */

This is the code for 'error_internal'/1 (although it is directly called
from 'error'/1).

...

> Index: runtime/mercury_stack_trace.h
> ===================================================================
> RCS file: /home/staff/zs/imp/mercury/runtime/mercury_stack_trace.h,v
> retrieving revision 1.2
> diff -u -r1.2 mercury_stack_trace.h
> --- mercury_stack_trace.h	1998/04/07 05:23:07	1.2
> +++ mercury_stack_trace.h	1998/04/07 09:12:14
> @@ -16,8 +16,21 @@
>  
>  /*
>  ** MR_dump_stack:
> -** 	Given the succip and det stack pointer, generate a stack dump
> -** 	showing then name of each active procedure on the stack.
> +** 	Given the succip, det stack pointer and current frame, generate a 
> +** 	stack dump showing then name of each active procedure on the

s/then/the/

> +** 	stack.
> +** 	NOTE: MR_dump_stack will assume that the succip is for the
> +** 	topmost stack frame.  If you call MR_dump_stack from some
> +** 	pragma c_code that may not be the case.
> +** 	Due to some optimizations (or lack thereof) the MR_dump_stack call 
> +** 	may end up inside code that has a stack frame allocated, but a

s/but a/but that/

or something equivalent

> +** 	has a succip for the previous stack frame.
> +** 	Don't call MR_dump_stack from Mercury pragma c_code (calling
> +** 	from other C code in the runtime is probably ok, provided the
> +** 	succip corresponds to the topmost stack frame).
> +** 	If you need more convienent calling from Mercury code, it would
> +** 	probably be best to make an impure predicate defined as using
> +** 	`:- external'.
>  */

Perhaps you could refer the reader to the example in require.m?

>  
>  extern void MR_dump_stack(Code *success_pointer, Word *det_stack_pointer,
> 

Everything else looks fine.

Cheers,
Mark
-- 
Mark Brown  (dougl at cs.mu.oz.au)             |  Any technology that is
MEngSc student,                             |  distinguishable from magic
Dept of Computer Science, Melbourne Uni     |  is insufficiently advanced