BUG: Fix PyArray_ZeroContiguousBuffer (resize) with struct dtypes

We allow the structured dtype to return NULL for the zero fill
function to indicate that a simple memset is sufficient.

Also simplifies error handling a bit.  The get_fill_zero_loop
function must clean up on error and not return references if
returns a `NULL` loop.

Author: seberg

numpy/_core/src/multiarray/refcount.c

@@ -83,25 +83,23 @@ PyArray_ZeroContiguousBuffer(
         if (get_fill_zero_loop(
                     NULL, descr, aligned, descr->elsize, &(zero_info.func),
                     &(zero_info.auxdata), &flags_unused) < 0) {
-            goto fail;
+            return -1;
         }
     }
     else {
+        assert(zero_info.func == NULL);
+    }
+    if (zero_info.func == NULL) {
         /* the multiply here should never overflow, since we already
            checked if the new array size doesn't overflow */
         memset(data, 0, size*stride);
-        NPY_traverse_info_xfree(&zero_info);
         return 0;
     }
 
     int res = zero_info.func(
             NULL, descr, data, size, stride, zero_info.auxdata);
     NPY_traverse_info_xfree(&zero_info);
     return res;
-
-  fail:
-    NPY_traverse_info_xfree(&zero_info);
-    return -1;
 }
 
 

numpy/_core/tests/test_multiarray.py

@@ -9174,6 +9174,12 @@ def test_resize(self):
             d.resize(150)
             assert_(old < sys.getsizeof(d))
 
+        @pytest.mark.parametrize("dtype", ["u4,f4", "u4,O"])
+        def test_resize_structured(self, dtype):
+            a = np.array([(0, 0.0) for i in range(5)], dtype=dtype)
+            a.resize(1000)
+            assert_array_equal(a, np.zeros(1000, dtype=dtype))
+
         def test_error(self):
             d = np.ones(100)
             assert_raises(TypeError, d.__sizeof__, "a")