[Python-Dev] Re: [Python-checkins] CVS: python/dist/src/Objects classobject.c,2.82,2.83

[Greg Stein]

I didn't have the heart to keep pestering Moshe, so I delayed a bit on the
latest round (and then left town for a few days). As a result, I didn't
get a chance to comment on this last patch.

There is one problem, and some formatting nits...

On Mon, 28 Feb 2000, Guido van Rossum wrote:
>...
> + static int instance_contains(PyInstanceObject *inst, PyObject *member)
> + {
> + 	static PyObject *__contains__;
> + 	PyObject *func, *arg, *res;
> + 	int ret;
> + 
> + 	if(__contains__ == NULL) {

"Standard Guido Formatting" requires a space between the "if" and the "(".
if, for, while, etc are not functions... they are language constructs.

>...
> + 			if(PyObject_Cmp(obj, member, &cmp_res) == -1)
> + 				ret = -1;
> + 			if(cmp_res == 0) 
> + 				ret = 1;
> + 			Py_DECREF(obj);
> + 			if(ret)
> + 				return ret;

I had suggested to Moshe to follow the logic in PySequence_Contains(), but
he wanted to use PyObject_Cmp() instead. No biggy, but the above code has
a bug:

PyObject_Cmp() does *not* guarantee a value for cmp_res if it returns -1.
Therefore, it is possible for cmp_res to be zero despite an error being
returned from PyObject_Cmp. Thus, you get a false-positive hit.

IMO, this section of code should read:

  cmp_res = PyObject_Compare(obj, member);
  Py_XDECREF(obj);
  if (cmp_res == 0)
      return 1;
  if (PyErr_Occurred())
      return -1;

The "ret" variable becomes unused and can be deleted. Oh! Just noted that
"ret" is declared twice; one hiding the declaration of the other. With the
above change and deletion of the inner "ret", then the hiding declaration
problem is also fixed.

Cheers,
-g

-- 
Greg Stein, http://www.lyra.org/