Re: HV to C struct

[Steve Hay]

Shinar, Tamar wrote:

Nick,

Thank you for the suggestions.  I think I have made my 'get' functions safe now.  

However, the external C library still behaves unstably on the data I pass it from perl.
It will sometimes core dump with SEGV, sometimes give unexpected output.
_____________________________________________________________________
The 1st thing to notice is that return from hv_fetch can be NULL if field
does not exist in the hash. So SvOK(*sv) will core dump, also you go on 
to de-ref the thing even if your test said SV was not okay.

So you want something like this - you can provide "safe" values for 
not-there and undef cases - I have used NULL and "" as examples.
 SV **svp = hv_fetch(...)
 if (*svp) {

I think the above line should have been

   if (svp) {

The point of the check is to ensure that you don't de-ref svp (i.e. 
don't use *svp) if svp is NULL.

This could explain your continued core dumps.

Steve

    if (SvOK(*svp)) {
      /* defined value of some kind (but may not be a string, but SvPV will
         force that for us). In perl5.6+ you may need to consider case 
         of string being in UTF-8
       */ 
      return SvPV_nolen(*svp);
    }
    else
     {
      /* undef value */
      return "";
     }
 }
 else {
   /* No such member */
   return NULL;
 }