On Sun, Feb 8, 2009 at 12:49 PM, Darren Dale <dsdale24@gmail.com> wrote:

I am seeing some really strange behavior when I try to pass an ndarray subclass and out=None to numpy's ufuncs. This example will reproduce the problem with svn numpy, the first print statement yields 1 as expected, the second yields "<type 'builtin_function_or_method'>" and the third yields a segmentation fault:

import numpy as np

class MyArray(np.ndarray):

    __array_priority__ = 20

    def __new__(cls):
        return np.asarray(1).view(cls).copy()

    def __repr__(self):
        return 'my_array'

    __str__ = __repr__

    def __mul__(self, other):
        return super(MyArray, self).__mul__(other)

    def __rmul__(self, other):
        return super(MyArray, self).__rmul__(other)

mine = MyArray()
print np.multiply(1, 1, None)
x = np.multiply(mine, mine, None)
print type(x)
print x

I think I might have found a fix for this. The following patch allows my script to run without a segfault:

$ svn diff
Index: umath_ufunc_object.inc
===================================================================
--- umath_ufunc_object.inc      (revision 6566)
+++ umath_ufunc_object.inc      (working copy)
@@ -3212,13 +3212,10 @@
         output_wrap[i] = wrap;
         if (j < nargs) {
             obj = PyTuple_GET_ITEM(args, j);
-            if (obj == Py_None) {
-                continue;
-            }
             if (PyArray_CheckExact(obj)) {
                 output_wrap[i] = Py_None;
             }
-            else {
+            else if (obj != Py_None) {
                 PyObject *owrap = PyObject_GetAttrString(obj,"__array_wrap__");
                 incref = 0;
                 if (!(owrap) || !(PyCallable_Check(owrap))) {

That call to continue skipped this bit of code in the loop, which is apparently important:

        if (incref) {
            Py_XINCREF(output_wrap[i]);
        }

I've tested the trunk on 64 bit linux, with and without this patch applied, and I get the same result in both cases: 1 known failure, 11 skips. Is there any chance someone could consider applying this patch before 1.3 ships?

Darren