[Gdal-dev] Re: DISOWN in ogr.i

[Charlie Savage]

Well from the SWIG changes file:

10/25/2005: mmatus
    - Perl, complete the DISOWN typemap.

If you look in perlrun.swg (SWIG 1.3.29):

SWIG_Perl_ConvertPtr(SWIG_MAYBE_PERL_OBJECT SV *sv, void **ptr, 
swig_type_info *_t, int flags) {

   ...

   /*
    *  DISOWN implementation: we need a perl guru to check this one.
    */
   if (tsv && (flags & SWIG_POINTER_DISOWN)) {
     /*
      *  almost copy paste code from below SWIG_POINTER_OWN setting
      */
     SV *obj = sv;
     HV *stash = SvSTASH(SvRV(obj));
     GV *gv = *(GV**) hv_fetch(stash, "OWNER", 5, TRUE);
     if (isGV(gv)) {
       HV *hv = GvHVn(gv);
       /*
        * To set ownership (see below), a newSViv(1) entry is added.
        * Hence, to remove ownership, we delete the entry.
        */
       if (hv_exists_ent(hv, obj, 0)) {
	hv_delete_ent(hv, obj, 0, 0);
       }
     }
   }
   return SWIG_OK;
}

I don't know any Perl - but this looks at least somewhat like the 
equivalent Ruby code.  There is also %delobject, see:

http://www.swig.org/Doc1.3/Customization.html#ownership

If this is the same DISOWN as Ruby/Python, I suppose that would be 
another argument for using SWIG 1.3.29 since it would avoid special 
cases for Perl.

Thanks,

Charlie


Ari Jolma wrote:
> Charlie Savage kirjoitti:
>> Hi Ari,
>>
>>> There has been three warnings on *DISOWN when generating the Perl 
>>> bindings. These have come from swig/include/ogr.i. As I understand 
>>> swig/Perl does not use *DISOWN, so I commented them out for Perl. 
>>
>> According to the SWIG documentation Perl does support DISOWN - see 
>> http://www.swig.org/Doc1.3/Perl5.html#Perl5_nn42.  I think this might 
>> be a newer feature.
> 
> The DISOWN method, which swig generates for Perl, is for the Perl 
> programmer to use, and does not automate the handing of the object from 
> Perl to C. This is an unnecessary extra task for him/her so I'd like the 
> bindings to do it, as it assumably does for the other languages. Now a 
> (not "the") solution (with swig 1.2.25 at least) is to write %perlcode 
> into the bindings to explicitly call DISOWN in these few cases 
> (SetGeometryDirectly etc).
> 
> Regarding the files in the CVS and swig version, I'd think that would be 
> a task for the PSC to decide ;-)
> 
> Just a few thoughts: Are people developing GDAL in Windows? Couldn't 
> there be a nightly make dist for those who need a bleeding edge version? 
> The Fedora 5 still has swig 1.3.24, installing 1.3.29 is an extra step, 
> which is not needed for Perl bindings I believe.
> 
> Thanks for the replies.
> 
> Ari
>