BUG: core: PyArray_NewFromDescr needs to update flags when strides != NULL (fixes numpy#1863

This appears to have been a longstanding bug, but has come to the
surface because PyArray_NewLikeArray uses the function with a non-NULL
strides parameter and is used more frequently then other such uses.

Author: Mark Wiebe

numpy/core/src/multiarray/ctors.c

@@ -1073,6 +1073,14 @@ PyArray_NewFromDescr(PyTypeObject *subtype, PyArray_Descr *descr, int nd,
     }
     self->data = data;
 
+    /*
+     * If the strides were provided to the function, need to
+     * update the flags to get the right CONTIGUOUS, ALIGN properties
+     */
+    if (strides != NULL) {
+        PyArray_UpdateFlags(self, UPDATE_ALL);
+    }
+
     /*
      * call the __array_finalize__
      * method if a subtype.
@@ -1083,13 +1091,6 @@ PyArray_NewFromDescr(PyTypeObject *subtype, PyArray_Descr *descr, int nd,
 
         func = PyObject_GetAttrString((PyObject *)self, "__array_finalize__");
         if (func && func != Py_None) {
-            if (strides != NULL) {
-                /*
-                 * did not allocate own data or funny strides
-                 * update flags before finalize function
-                 */
-                PyArray_UpdateFlags(self, UPDATE_ALL);
-            }
             if (NpyCapsule_Check(func)) {
                 /* A C-function is stored here */
                 PyArray_FinalizeFunc *cfunc;

numpy/core/tests/test_numeric.py

@@ -1227,6 +1227,8 @@ def check_like_function(self, like_function, value):
             assert_equal(dz.shape, d.shape)
             assert_equal(array(dz.strides)*d.dtype.itemsize,
                          array(d.strides)*dz.dtype.itemsize)
+            assert_equal(d.flags.c_contiguous, dz.flags.c_contiguous)
+            assert_equal(d.flags.f_contiguous, dz.flags.f_contiguous)
             if dtype is None:
                 assert_equal(dz.dtype, d.dtype)
             else: