Merge pull request numpy#15882 from eric-wieser/reject-illegal-stride…

…s-in-ndarray.__new__

BUG: Do not ignore empty tuple of strides in ndarray.__new__

doc/release/upcoming_changes/15882.compatibility.rst

@@ -0,0 +1,5 @@
+The ``numpy.ndarray`` constructor no longer interprets ``strides=()`` as ``strides=None``
+-----------------------------------------------------------------------------------------
+The former has changed to have the expected meaning of setting
+`numpy.ndarray.strides` to ``()``, while the latter continues to result in
+strides being chosen automatically.

numpy/core/src/multiarray/arrayobject.c

@@ -41,6 +41,7 @@ maintainer email:  [email protected]
 #include "arraytypes.h"
 #include "scalartypes.h"
 #include "arrayobject.h"
+#include "conversion_utils.h"
 #include "ctors.h"
 #include "methods.h"
 #include "descriptor.h"
@@ -1624,7 +1625,7 @@ array_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds)
     PyArray_Descr *descr = NULL;
     int itemsize;
     PyArray_Dims dims = {NULL, 0};
-    PyArray_Dims strides = {NULL, 0};
+    PyArray_Dims strides = {NULL, -1};
     PyArray_Chunk buffer;
     npy_longlong offset = 0;
     NPY_ORDER order = NPY_CORDER;
@@ -1645,7 +1646,7 @@ array_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds)
                                      PyArray_BufferConverter,
                                      &buffer,
                                      &offset,
-                                     &PyArray_IntpConverter,
+                                     &PyArray_OptionalIntpConverter,
                                      &strides,
                                      &PyArray_OrderConverter,
                                      &order)) {
@@ -1660,7 +1661,7 @@ array_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds)
 
     itemsize = descr->elsize;
 
-    if (strides.ptr != NULL) {
+    if (strides.len != -1) {
         npy_intp nb, off;
         if (strides.len != dims.len) {
             PyErr_SetString(PyExc_ValueError,

numpy/core/src/multiarray/conversion_utils.c

@@ -137,6 +137,20 @@ PyArray_IntpConverter(PyObject *obj, PyArray_Dims *seq)
     return NPY_SUCCEED;
 }
 
+/*
+ * Like PyArray_IntpConverter, but leaves `seq` untouched if `None` is passed
+ * rather than treating `None` as `()`.
+ */
+NPY_NO_EXPORT int
+PyArray_OptionalIntpConverter(PyObject *obj, PyArray_Dims *seq)
+{
+    if (obj == Py_None) {
+        return NPY_SUCCEED;
+    }
+
+    return PyArray_IntpConverter(obj, seq);
+}
+
 /*NUMPY_API
  * Get buffer chunk from object
  *

numpy/core/src/multiarray/conversion_utils.h

@@ -6,6 +6,9 @@
 NPY_NO_EXPORT int
 PyArray_IntpConverter(PyObject *obj, PyArray_Dims *seq);
 
+NPY_NO_EXPORT int
+PyArray_OptionalIntpConverter(PyObject *obj, PyArray_Dims *seq);
+
 NPY_NO_EXPORT int
 PyArray_BufferConverter(PyObject *obj, PyArray_Chunk *buf);
 

numpy/core/tests/test_multiarray.py

@@ -679,6 +679,12 @@ def test_constructor(self):
         y[()] = 6
         assert_equal(x[()], 6)
 
+        # strides and shape must be the same length
+        with pytest.raises(ValueError):
+            np.ndarray((2,), strides=())
+        with pytest.raises(ValueError):
+            np.ndarray((), strides=(2,))
+
     def test_output(self):
         x = np.array(2)
         assert_raises(ValueError, np.add, x, [1], x)