RE: Am I checking for undef in the wrong way?

On Thu, 23 Jul 2009, Erland Sommarskog wrote:
> 
> "Jan Dubois" ([email protected]) writes:
> > This can happen with other magical SVs too.  You must call SvGETMAGIC()
> > before you can trust the SVf_?OK flags.  SvIV() will do this as a side
> > effect.
> 
> Thus, in any place where I receive a value of which I don't know the
> origin, I should call SvGETMAGIC first. I could then just as well
> have
> 
>   BOOL sv_isdefined(SV *sv) {
>      SvGETMAGIC(sv);
>      return SvOK(sv);
>   }
>
>
> Or would this lead in my new problems?

You should pass in the Perl context so it works under MULTIPLICITY (and
by extension under USE_ITHREADS):


    #define sv_isdefined(sv) my_is_defined(aTHX_ sv)

    static BOOL
    my_sv_isdefined(pTHX_ SV *sv) {
        ...
    }

Drop the "static" and move the #define into a header file if you need to
call it from more than one source file.

Cheers,
-Jan