Hi, hopefully this is pretty straightforward.
I'm using perl v5.6.1 and building an XS wrapper around
FreeBSD's kevent/kqueue functions.
The library passes around poiunters to structures,
which I'm blessing into a package using the T_PTROBJ
typemap entry.
This works fine if the pointers are non-null, but if I
return a null pointer, it seems like the blessing fails.
The code is pretty simple:
/* Kqueue.xs */
typedef struct kevent *_Kevent;
...
MODULE = Kqueue PACKAGE = _Kevent
...
_Kevent
create(size=1)
u_int size
CODE:
if (size > 0) {
RETVAL = (_Kevent) calloc(size, sizeof(struct kevent));
} else {
RETVAL = (_Kevent) 0;
}
OUTPUT:
RETVAL
...
MODULE = Kqueue PACKAGE = Kqueue
int
_kevent(kq, changelist, nchanges, eventlist, nevents, timeout = NULL)
Kqueue kq
_Kevent changelist
int nchanges
_Kevent eventlist
int nevents
Timeout timeout
INIT:
/* typemap */
_Kevent T_PTROBJ
The call to Kqueue::_kevent() fails with:
Use of uninitialized value in subroutine entry at blib/lib/Kqueue.pm line 228.
eventlist is not of type _Kevent at blib/lib/Kqueue.pm line 228.
Where eventlist is what _Kevent::create(0) returned, i.e. a blessed reference to a
null pointer.
On inspection of the C output, this reduces to
ST(0) = sv_newmortal();
sv_setref_pv(ST(0), "_Kevent", (void*)0);
Does sv_setref_pv assume undef if its 3rd arg is null?
--
Bill Hails, Technical Yahoo! Y!M:billhails +44(0)20 7808 4457
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