New subject: [cffi-devel] CFFI-USER: Dereferencing an address to a pointer array ... ? SOLVED!

17 Nov 2007


      Hi all:
I have in C  in a library:
typedef struct  __tsPMDevInfo
{
    ... some slots in here; don't matter ...
} tsPMDevInfo, *ptsPMDevInfoPtr;
//  
------------------------------------------------------------------------
// nFindPMs -- Find PM Devices on all available serials
//  
------------------------------------------------------------------------ 
-
int nFindPMs( ptsPMDevInfoPtr **pppsPMDevInfoArray,
                           int *pnNrPMsFound )
{
   int nRC = 0;
ptsPMDevInfoPtr *ppsPMDevInfoArray = NULL;
.... Here, memory gets allocated and
  ppsPMDevInfoArray points to an array of
pointers to struct tsPMDevInfo !
if( pppsPMDevInfoArray != NULL )
     *pppsPMDevInfoArray = ppsPMDevInfoArray;
if( pnNrPMsFound != NULL )
     *pnNrPMsFound = nNrPMs;
if( nNrPMs > 0 )
     nRC = PMIO_RC_OK;
   else
     nRC = PMIO_RC_NO_PM_FOUND;
return nRC;
}
In Lisp-land I do (simplified):
(defcfun ("nFindPMs" %nFindPMs) pmio-rc
   (ppsPMDevInfoPtr :pointer)
   (pnNrPMs         :pointer))
(defun find-pms (ppsPMDevInfoPtr pnNrPMs)
   (%nFindPMs ppsPMDevInfoPtr pnNrPMs))
I do get a valid value for the nr of PMs back with
(mem-ref pnNrPMs :int 0)
But I am unable to get a valid foreign pointer back for  
ppsPMDevInfoPtr :
(mem-ref ppsPMDebInfoPtr :pointer 0)
always returns an invalid value (no valid memory address). So, the  
question is: How do I return a pointer to an array of pointers ?
In C land everything is OK and the pointer array is valid: check via  
ppsPMDebInfoPtr[0] -> This is the pointer to a valid struct tsPMDevInfo.
Thx for any pointers ;-) !!!
Frank