Address Bénédikt's review

Author: vstinner

Doc/c-api/long.rst

@@ -657,7 +657,7 @@ distinguished from a number.  Use :c:func:`PyErr_Occurred` to disambiguate.
 Export API
 ^^^^^^^^^^
 
-.. versionadded:: 3.14
+.. versionadded:: next
 
 .. c:struct:: PyLongLayout
 
@@ -692,7 +692,7 @@ Export API
       Digit endianness:
 
       - ``1`` for most significant byte first (big endian)
-      - ``-1`` for least significant first (little endian)
+      - ``-1`` for least significant byte first (little endian)
 
 
 .. c:function:: const PyLongLayout* PyLong_GetNativeLayout(void)
@@ -743,6 +743,8 @@ Export API
 
    Export a Python :class:`int` object.
 
+   *export_long* must not be ``NULL``.
+
    On success, set *\*export_long* and return ``0``.
    On error, set an exception and return ``-1``.
 
@@ -760,7 +762,7 @@ PyLongWriter API
 
 The :c:type:`PyLongWriter` API can be used to import an integer.
 
-.. versionadded:: 3.14
+.. versionadded:: next
 
 .. c:struct:: PyLongWriter
 
@@ -789,7 +791,7 @@ The :c:type:`PyLongWriter` API can be used to import an integer.
    :c:func:`PyLongWriter_Discard` to destroy the writer instance.  Digits must
    be in the range [``0``; ``(1 << bits_per_digit) - 1``]  (where the
    :c:struct:`~PyLongLayout.bits_per_digit` is the number of bits per digit).
-   The unused most-significant digits must be set to ``0``.
+   The unused most significant digits must be set to ``0``.
 
 
 .. c:function:: PyObject* PyLongWriter_Finish(PyLongWriter *writer)
@@ -809,4 +811,6 @@ The :c:type:`PyLongWriter` API can be used to import an integer.
 
    Discard a :c:type:`PyLongWriter` created by :c:func:`PyLongWriter_Create`.
 
+   *writer* must not be ``NULL``.
+
    The writer instance is invalid after the call.

Lib/test/test_capi/test_long.py

@@ -738,12 +738,15 @@ def test_long_export(self):
         self.assertEqual(pylong_export(0), 0)
         self.assertEqual(pylong_export(123), 123)
         self.assertEqual(pylong_export(-123), -123)
+        self.assertEqual(pylong_export(IntSubclass(123)), 123)
 
         # use an array, doesn't fit into int64_t
         self.assertEqual(pylong_export(base**10 * 2 + 1),
                          (0, [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2]))
         self.assertEqual(pylong_export(-(base**10 * 2 + 1)),
                          (1, [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2]))
+        self.assertEqual(pylong_export(IntSubclass(base**10 * 2 + 1)),
+                         (0, [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2]))
 
         for value in (1.0, 0+1j, "abc"):
             with self.subTest(value=value):

Modules/_testcapi/long.c

@@ -193,6 +193,9 @@ pylong_export(PyObject *module, PyObject *obj)
     const digit *export_long_digits = export_long.digits;
 
     PyObject *digits = PyList_New(0);
+    if (digits == NULL) {
+        goto error;
+    }
     for (Py_ssize_t i = 0; i < export_long.ndigits; i++) {
         PyObject *item = PyLong_FromUnsignedLong(export_long_digits[i]);
         if (item == NULL) {
@@ -214,7 +217,7 @@ pylong_export(PyObject *module, PyObject *obj)
     return res;
 
 error:
-    Py_DECREF(digits);
+    Py_XDECREF(digits);
     PyLong_FreeExport(&export_long);
     return NULL;
 }
@@ -225,8 +228,7 @@ pylongwriter_create(PyObject *module, PyObject *args)
 {
     int negative;
     PyObject *list;
-    if (!PyArg_ParseTuple(args, "iO!", &negative, &PyList_Type, &list))
-    {
+    if (!PyArg_ParseTuple(args, "iO!", &negative, &PyList_Type, &list)) {
         return NULL;
     }
     Py_ssize_t ndigits = PyList_GET_SIZE(list);

Objects/longobject.c

@@ -6853,20 +6853,24 @@ PyLongWriter_Create(int negative, Py_ssize_t ndigits, void **digits)
 {
     if (ndigits <= 0) {
         PyErr_SetString(PyExc_ValueError, "ndigits must be positive");
-        return NULL;
+        goto error;
     }
     assert(digits != NULL);
 
     PyLongObject *obj = _PyLong_New(ndigits);
     if (obj == NULL) {
-        return NULL;
+        goto error;
     }
     if (negative) {
         _PyLong_FlipSign(obj);
     }
 
     *digits = obj->long_value.ob_digit;
     return (PyLongWriter*)obj;
+
+error:
+    *digits = NULL;
+    return NULL;
 }