On Fri, Sep 08, 2006 at 06:27:08PM -0400, Barry Warsaw wrote:
>
> On Sep 8, 2006, at 6:06 PM, Mihai Ibanescu wrote:
>
> >There is no description of what happens when Py_BuildValue fails.
> >Will it
> >decref the python object passed in? Will it not?
>
> I just want to point out that the C API documentation is pretty
> silent about the refcounting side-effects in error conditions (and
> often in success conditions too) of most Python functions. For
> example, what is the refcounting side-effects of PyDict_SetItem() on
> val? What about if that function fails? Has val been incref'd or
> not? What about the side-effects on any value the new one replaces,
> both in success and failure?
In this particular case, it doesn't decref it (or so I read the code).
Relevant code is in do_mkvalue from Python/modsupport.c
case 'N':
case 'S':
case 'O':
if (**p_format == '&') {
typedef PyObject *(*converter)(void *);
converter func = va_arg(*p_va, converter);
void *arg = va_arg(*p_va, void *);
++*p_format;
return (*func)(arg);
}
else {
PyObject *v;
v = va_arg(*p_va, PyObject *);
if (v != NULL) {
if (*(*p_format - 1) != 'N')
Py_INCREF(v);
}
else if (!PyErr_Occurred())
/* If a NULL was passed
* because a call that should
* have constructed a value
* failed, that's OK, and we
* pass the error on; but if
* no error occurred it's not
* clear that the caller knew
* what she was doing. */
PyErr_SetString(PyExc_SystemError,
"NULL object passed to
Py_BuildValue");
return v;
}
Barry, where can I ship you my cloning machine? :-)
Misa
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