BUG: Fix arr.flat.index for large arrays and big-endian machines

numpy/core/src/multiarray/conversion_utils.c

@@ -1222,11 +1222,7 @@ PyArray_IntTupleFromIntp(int len, npy_intp const *vals)
         goto fail;
     }
     for (i = 0; i < len; i++) {
-#if NPY_SIZEOF_INTP <= NPY_SIZEOF_LONG
-        PyObject *o = PyLong_FromLong((long) vals[i]);
-#else
-        PyObject *o = PyLong_FromLongLong((npy_longlong) vals[i]);
-#endif
+        PyObject *o = PyArray_PyIntFromIntp(vals[i]);
         if (!o) {
             Py_DECREF(intTuple);
             intTuple = NULL;

numpy/core/src/multiarray/conversion_utils.h

@@ -39,6 +39,17 @@ PyArray_IntpFromSequence(PyObject *seq, npy_intp *vals, int maxvals);
 NPY_NO_EXPORT int
 PyArray_TypestrConvert(int itemsize, int gentype);
 
+
+static NPY_INLINE PyObject *
+PyArray_PyIntFromIntp(npy_intp const value)
+{
+#if NPY_SIZEOF_INTP <= NPY_SIZEOF_LONG
+    return PyLong_FromLong((long)value);
+#else
+    return PyLong_FromLongLong((npy_longlong)value);
+#endif
+}
+
 NPY_NO_EXPORT PyObject *
 PyArray_IntTupleFromIntp(int len, npy_intp const *vals);
 

numpy/core/src/multiarray/getset.c

@@ -419,33 +419,13 @@ array_itemsize_get(PyArrayObject *self)
 static PyObject *
 array_size_get(PyArrayObject *self)
 {
-    npy_intp size=PyArray_SIZE(self);
-#if NPY_SIZEOF_INTP <= NPY_SIZEOF_LONG
-    return PyLong_FromLong((long) size);
-#else
-    if (size > NPY_MAX_LONG || size < NPY_MIN_LONG) {
-        return PyLong_FromLongLong(size);
-    }
-    else {
-        return PyLong_FromLong((long) size);
-    }
-#endif
+    return PyArray_PyIntFromIntp(PyArray_SIZE(self));
 }
 
 static PyObject *
 array_nbytes_get(PyArrayObject *self)
 {
-    npy_intp nbytes = PyArray_NBYTES(self);
-#if NPY_SIZEOF_INTP <= NPY_SIZEOF_LONG
-    return PyLong_FromLong((long) nbytes);
-#else
-    if (nbytes > NPY_MAX_LONG || nbytes < NPY_MIN_LONG) {
-        return PyLong_FromLongLong(nbytes);
-    }
-    else {
-        return PyLong_FromLong((long) nbytes);
-    }
-#endif
+    return PyArray_PyIntFromIntp(PyArray_NBYTES(self));
 }
 
 

numpy/core/src/multiarray/iterators.c

@@ -15,6 +15,7 @@
 #include "iterators.h"
 #include "ctors.h"
 #include "common.h"
+#include "conversion_utils.h"
 #include "array_coercion.h"
 
 #define NEWAXIS_INDEX -1
@@ -1062,13 +1063,15 @@ static PyMemberDef iter_members[] = {
         T_OBJECT,
         offsetof(PyArrayIterObject, ao),
         READONLY, NULL},
-    {"index",
-        T_INT,
-        offsetof(PyArrayIterObject, index),
-        READONLY, NULL},
     {NULL, 0, 0, 0, NULL},
 };
 
+static PyObject *
+iter_index_get(PyArrayIterObject *self)
+{
+    return PyArray_PyIntFromIntp(self->index);
+}
+
 static PyObject *
 iter_coords_get(PyArrayIterObject *self)
 {
@@ -1095,10 +1098,12 @@ iter_coords_get(PyArrayIterObject *self)
 }
 
 static PyGetSetDef iter_getsets[] = {
+    {"index",
+        (getter)iter_index_get,
+        NULL, NULL, NULL},
     {"coords",
         (getter)iter_coords_get,
-        NULL,
-        NULL, NULL},
+        NULL, NULL, NULL},
     {NULL, NULL, NULL, NULL, NULL},
 };
 
@@ -1410,31 +1415,13 @@ arraymultiter_dealloc(PyArrayMultiIterObject *multi)
 static PyObject *
 arraymultiter_size_get(PyArrayMultiIterObject *self)
 {
-#if NPY_SIZEOF_INTP <= NPY_SIZEOF_LONG
-    return PyLong_FromLong((long) self->size);
-#else
-    if (self->size < NPY_MAX_LONG) {
-        return PyLong_FromLong((long) self->size);
-    }
-    else {
-        return PyLong_FromLongLong((npy_longlong) self->size);
-    }
-#endif
+    return PyArray_PyIntFromIntp(self->size);
 }
 
 static PyObject *
 arraymultiter_index_get(PyArrayMultiIterObject *self)
 {
-#if NPY_SIZEOF_INTP <= NPY_SIZEOF_LONG
-    return PyLong_FromLong((long) self->index);
-#else
-    if (self->size < NPY_MAX_LONG) {
-        return PyLong_FromLong((long) self->index);
-    }
-    else {
-        return PyLong_FromLongLong((npy_longlong) self->index);
-    }
-#endif
+    return PyArray_PyIntFromIntp(self->index);
 }
 
 static PyObject *

numpy/core/tests/test_multiarray.py

@@ -5364,6 +5364,17 @@ def test_refcount(self):
             assert_(abs(sys.getrefcount(ind) - rc_ind) < 50)
             assert_(abs(sys.getrefcount(indtype) - rc_indtype) < 50)
 
+    def test_index_getset(self):
+        it = np.arange(10).reshape(2, 1, 5).flat
+        with pytest.raises(AttributeError):
+            it.index = 10
+
+        for _ in it:
+            pass
+        # Check the value of `.index` is updated correctly (see also gh-19153)
+        # If the type was incorrect, this would show up on big-endian machines
+        assert it.index == it.base.size
+
 
 class TestResize: