On Fri, 8 Mar 2002, Stas Bekman wrote:
> Doug,
>
> This kind of construct:
>
> int mpxs_Apache__Foo_bar(pTHX_ I32 items, SV **MARK, SV **SP)
>
> is special to WrapXS, isn't it?
dunno if i'd call it special. usage is derived from PP() functions in the
perl core.
> you cannot really use ST() macros inside of it to access arguments on
> the stack. I see that 'ax' + PL_stack_base don't point to the first
> argument, but to the second one. Though MARK does point to the first
> argument, so what I get is:
>
> first arg: *MARK
> second arg: *(MARK+1) == ST(0)
> ...
>
> I've read through the sources and it seems that you manipulate the stack
> only via MARK in this kind of mpxs_ functions.
right.
> Is this because of the second non-XSUB call from within the XS wrapper?
> And ST() macros are designed only to be used inside the XSUB calls?
ST() could be used anywhere, the MARK/SP usage is just a little less
overhead. and this is only used for variable number of args, like
print(...):
while (MARK <= SP) {
char *buf = SvPV(*MARK, wlen);
...
MARK++;
}
if you know the number of arguments you shouldn't be using this construct.
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