[m-rev.] refactor nondet stack traversal code

[Fergus Henderson]

On 11-Nov-2003, Zoltan Somogyi <zs at cs.mu.OZ.AU> wrote:
> On 08-Nov-2003, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> >  static const char *
> > -MR_step_over_nondet_frame(FILE *fp, int level_number, MR_Word *fr)
> > +MR_step_over_nondet_frame(MR_Traverse_Nondet_Frame_Func *func,
> > +    void *func_data, FILE *dump_fp, int level_number, MR_Word *fr)
> 
> For the agc version, you wouldn't want to pass in a FILE *.

For the agc version, the code passes in NULL.

Note that this function with a FILE * parameter is static; the collector
doesn't call this function directly,l it calls an exported (extern
linkage) function in this file which does not have a FILE * parameter,
and that function calls this one passing NULL.  So the use of a FILE *
parameter here is an implementation detail that is internal to this
source file.

> I don't see any reason why I/O should happen in MR_step_over_nondet_frame
> instead of in func.

The reason for that is that when we're stepping over the "terminal top
frame of a nondet side branch", I/O happens, but func doesn't get called.

(That's not a bug, is it?  That is, is it right to not traverse the
variables in such a frame?)

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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