On Sun, 07 Sep 2003 09:49:32 +0200, Tassilo von Parseval
<[EMAIL PROTECTED]> wrote:
>Hi there,
>
>this is the strangest thing I've ever encountered so far with XS. To me
>it looks like a very obscure bug in perl, but hopefully it's not. The
>Perl examples actually use autobox, but the very same behaviour shows up
>when using a pure functional interface:
>
>I have a very basic C function that triggers a Perl callback:
>
> SV * call_Pslice (const char *func) {
> SV *res;
>
> dSP;
> ENTER;
> SAVETMPS;
> PUTBACK;
>
> (void)call_pv(func, G_SCALAR);
> SPAGAIN;
>
> res = newSVsv(POPs);
>
> PUTBACK;
> FREETMPS;
> LEAVE;
>
> return sv_2mortal(res);
> }
You are missing a PUSHMARK(xxx) call in here. The call_pv() will pop your
callers frame from the stack, and you caller doesn't seem to adjust for
it.
Two more unrelated notes:
1) You call sv_2mortal() on your result without checking if the result has
the SvREADONLY bit set. If the sub can return undef, you may be modifying
the refcount of an immortal, which doesn't matter in most cases as it
starts with a refcount of 2**31, but is still bad style (IMO).
2) Calling call_xxx() without G_EVAL often doesn't work correctly when
your Perl sub can die(). Maybe it is just cargo cult, but I've been
bitten by this one too many times and now always specify G_EVAL and check
SvTRUE(ERRSV) myself to handle exceptions myself.
Cheers,
-Jan
