Hello,
I'd like to be able to see the perl stack from a C routine,
which is in turn called from an XSUB. I'm obviously going about
this the wrong way, but I'd appreciate it if someone could point
out exactly how.
I have a file, foo.xs, which looks like this (ignoring the
includes at the top):
> void peekstack()
> {
> int i;
>
> dXSARGS;
>
> fprintf(stderr,"peekstack() sees %d items on the stack\n",
> items);
> for (i=0;i<items;i++) {
> fprintf(stderr,"\t\tST(%d)=\"%s\"\n",
> i,SvPV_nolen(ST(i)));
> }
> }
>
>
> MODULE = foo PACKAGE = foo
>
> void method(...)
> PREINIT:
> int i;
> CODE:
> fprintf(stderr,"method() can see %d items on the stack\n\t",
> items);
> peekstack();
> fflush(stderr);
What I would like is for peekstack() to be able to see exactly
the same stack context as method(). However, when I run it as
below, peekstack() sees a silly number of arguments on the
stack.
> % perl -Mblib -Mfoo -le 'for (1..3){foo->method();}
> method() can see 1 items on the stack
> peekstack() sees 3 items on the stack
> ST(0)="1"
> ST(1)="3"
> ST(2)="foo"
> method() can see 1 items on the stack
> peekstack() sees -134 items on the stack
> method() can see 1 items on the stack
> peekstack() sees 3 items on the stack
> ST(0)="1"
> ST(1)="3"
> ST(2)="foo"
> %
I can quite happily use PUSHMARK etc to set up a new stack
context before calling peekstack(), but then it can't see the
things that were passed to method(), which is what I'm after. Is
there some particular macro I should be using to do this?
Another (vaguely related) question:- as far as I can tell from
pp.h and friends, "dXSARGS;" will actually change some internal
state, by calling POPMARK. Is this the case?
-jc, who does not grok the perl stack.
