BUG: Fix deepcopy regression for empty arrays.

Deepcopy of empty arrays was failing because the nditer was constructed
without the NPY_ITER_ZEROSIZE_OK flag.

Closes #8536.

2 files changed, 36 insertions, 28 deletions

diff --git a/numpy/core/src/multiarray/methods.c b/numpy/core/src/multiarray/methods.c
index f2e1d87ad..80d4aebeb 100644
--- a/numpy/core/src/multiarray/methods.c
+++ b/numpy/core/src/multiarray/methods.c
@@ -1441,41 +1441,42 @@ array_deepcopy(PyArrayObject *self, PyObject *args)
             Py_DECREF(copied_array);
             return NULL;
         }
-        iter = (NpyIter *)NpyIter_New(copied_array,
-                                      (NPY_ITER_READWRITE |
-                                       NPY_ITER_EXTERNAL_LOOP |
-                                       NPY_ITER_REFS_OK),
-                                      NPY_KEEPORDER,
-                                      NPY_NO_CASTING,
-                                      NULL);
+        iter = NpyIter_New(copied_array,
+                           NPY_ITER_READWRITE |
+                           NPY_ITER_EXTERNAL_LOOP |
+                           NPY_ITER_REFS_OK |
+                           NPY_ITER_ZEROSIZE_OK,
+                           NPY_KEEPORDER, NPY_NO_CASTING,
+                           NULL);
         if (iter == NULL) {
             Py_DECREF(deepcopy);
             Py_DECREF(copied_array);
             return NULL;
         }
-        iternext = NpyIter_GetIterNext(iter, NULL);
-        if (iternext == NULL) {
-            NpyIter_Deallocate(iter);
-            Py_DECREF(deepcopy);
-            Py_DECREF(copied_array);
-            return NULL;
-        }
-
-        dataptr = NpyIter_GetDataPtrArray(iter);
-        strideptr = NpyIter_GetInnerStrideArray(iter);
-        innersizeptr = NpyIter_GetInnerLoopSizePtr(iter);
-
-        do {
-            data = *dataptr;
-            stride = *strideptr;
-            count = *innersizeptr;
-            while (count--) {
-                _deepcopy_call(data, data, PyArray_DESCR(copied_array),
-                               deepcopy, visit);
-                data += stride;
+        if (NpyIter_GetIterSize(iter) != 0) {
+            iternext = NpyIter_GetIterNext(iter, NULL);
+            if (iternext == NULL) {
+                NpyIter_Deallocate(iter);
+                Py_DECREF(deepcopy);
+                Py_DECREF(copied_array);
+                return NULL;
             }
-        } while (iternext(iter));
 
+            dataptr = NpyIter_GetDataPtrArray(iter);
+            strideptr = NpyIter_GetInnerStrideArray(iter);
+            innersizeptr = NpyIter_GetInnerLoopSizePtr(iter);
+
+            do {
+                data = *dataptr;
+                stride = *strideptr;
+                count = *innersizeptr;
+                while (count--) {
+                    _deepcopy_call(data, data, PyArray_DESCR(copied_array),
+                                   deepcopy, visit);
+                    data += stride;
+                }
+            } while (iternext(iter));
+        }
         NpyIter_Deallocate(iter);
         Py_DECREF(deepcopy);
     }
diff --git a/numpy/core/tests/test_regression.py b/numpy/core/tests/test_regression.py
index 721a025de..4875f852a 100644
--- a/numpy/core/tests/test_regression.py
+++ b/numpy/core/tests/test_regression.py
@@ -2094,6 +2094,13 @@ class TestRegression(TestCase):
         # Check the references hold for the copied objects.
         self.assertTrue(arr_cp[0, 1] is arr_cp[1, 1])
 
+    def test_deepcopy_empty_object_array(self):
+        # Ticket #8536.
+        # Deepcopy should succeed
+        a = np.array([], dtype=object)
+        b = copy.deepcopy(a)
+        assert_(a.shape == b.shape)
+
     def test_bool_subscript_crash(self):
         # gh-4494
         c = np.rec.array([(1, 2, 3), (4, 5, 6)])