BUG: Fix comparison of fieldless structured arrays

3 files changed, 16 insertions, 5 deletions

diff --git a/doc/source/reference/c-api/array.rst b/doc/source/reference/c-api/array.rst
index a2b56cee7..215584b62 100644
--- a/doc/source/reference/c-api/array.rst
+++ b/doc/source/reference/c-api/array.rst
@@ -997,6 +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.
+
 .. c:function:: PyTypeNum_ISUSERDEF(num)
 
 .. c:function:: PyDataType_ISUSERDEF(descr)
diff --git a/numpy/core/src/multiarray/arrayobject.c b/numpy/core/src/multiarray/arrayobject.c
index 4676c40d5..05e1d3011 100644
--- a/numpy/core/src/multiarray/arrayobject.c
+++ b/numpy/core/src/multiarray/arrayobject.c
@@ -1201,15 +1201,17 @@ _void_compare(PyArrayObject *self, PyArrayObject *other, int cmp_op)
         }
         if (res == NULL && !PyErr_Occurred()) {
             /* these dtypes had no fields */
-            return cmp_op == Py_EQ ? Py_True : Py_False;
+            res = PyArray_NewLikeArray(self, NPY_ANYORDER,
+                                       PyArray_DescrFromType(NPY_BOOL), 1);
+            if (res) {
+                 PyArray_FILLWBYTE((PyArrayObject*)res,
+                                   cmp_op == Py_EQ ? 1 : 0);
+            }
         }
         return res;
     }
     else {
-        /*
-         * compare as a string. Assumes self and
-         * other have same descr->type
-         */
+        /* compare as a string. Assumes self and other have same descr->type */
         return _strings_richcompare(self, other, cmp_op, 0);
     }
 }
diff --git a/numpy/core/tests/test_dtype.py b/numpy/core/tests/test_dtype.py
index 14c1857b4..6230b27b7 100644
--- a/numpy/core/tests/test_dtype.py
+++ b/numpy/core/tests/test_dtype.py
@@ -438,6 +438,12 @@ class TestRecord(object):
         assert_raises(ValueError, np.dtype, ([], 'f8'))
         assert_raises(ValueError, np.zeros(1, dtype='i4').view, [])
 
+        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))
+
 
 class TestSubarray(object):
     def test_single_subarray(self):