BUG: Fix fieldless comparison broadcasting

Fixes numpy#13438
kulinseth · Sep 5, 2019 · d6f7524 · d6f7524
1 parent 7c3adfb
commit d6f7524
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Showing 4 changed files with 24 additions and 8 deletions.
diff --git a/doc/release/upcoming_changes/14393.c_api.rst b/doc/release/upcoming_changes/14393.c_api.rst
@@ -0,0 +1,5 @@
+PyDataType_ISUNSIZED(descr) now returns False for structured datatypes
+----------------------------------------------------------------------
+Previously this returned True for any datatype of itemsize 0, but now this
+returns false for the non-flexible datatype with itemsize 0, ``np.dtype([])``.
+
diff --git a/doc/source/reference/c-api/array.rst b/doc/source/reference/c-api/array.rst
@@ -997,8 +997,9 @@ argument must be a :c:type:`PyObject *<PyObject>` that can be directly interpret
     called on flexible dtypes. Types that are attached to an array will always
     be sized, hence the array form of this macro not existing.
 
-    ..versionchanged:: 1.18.0
-    For structured datatypes with no fields this function now return False.
+    .. versionchanged:: 1.18
+
+    For structured datatypes with no fields this function now returns False.
 
 .. c:function:: PyTypeNum_ISUSERDEF(num)
 

diff --git a/numpy/core/src/multiarray/arrayobject.c b/numpy/core/src/multiarray/arrayobject.c
@@ -1200,11 +1200,21 @@ _void_compare(PyArrayObject *self, PyArrayObject *other, int cmp_op)
             }
         }
         if (res == NULL && !PyErr_Occurred()) {
-            /* these dtypes had no fields */
-            res = PyArray_NewLikeArray(self, NPY_ANYORDER,
-                                       PyArray_DescrFromType(NPY_BOOL), 1);
+            /* these dtypes had no fields. Use a MultiIter to broadcast them
+             * to an output array, and fill with True (for EQ)*/
+            PyArrayMultiIterObject *mit = (PyArrayMultiIterObject *)
+                                          PyArray_MultiIterNew(2, self, other);
+            if (mit == NULL) {
+                return NULL;
+            }
+
+            res = PyArray_NewFromDescr(&PyArray_Type,
+                                       PyArray_DescrFromType(NPY_BOOL),
+                                       mit->nd, mit->dimensions,
+                                       NULL, NULL, 0, NULL);
+            Py_DECREF(mit);
             if (res) {
-                 PyArray_FILLWBYTE((PyArrayObject*)res,
+                 PyArray_FILLWBYTE((PyArrayObject *)res,
                                    cmp_op == Py_EQ ? 1 : 0);
             }
         }

diff --git a/numpy/core/tests/test_dtype.py b/numpy/core/tests/test_dtype.py
@@ -441,8 +441,8 @@ def test_fieldless_views(self):
         assert_equal(np.zeros(2, dtype=[]) == np.zeros(2, dtype=[]),
                      np.ones(2, dtype=bool))
 
-        assert_equal(np.zeros(2, dtype=[]) == a,
-                     np.ones(2, dtype=bool))
+        assert_equal(np.zeros((1, 2), dtype=[]) == a,
+                     np.ones((1, 2), dtype=bool))
 
 
 class TestSubarray(object):