More reliable test

Author: zooba

Lib/test/test_capi/test_long.py

@@ -428,8 +428,8 @@ def test_long_asnativebytes(self):
         import math
         from _testcapi import (
             pylong_asnativebytes as asnativebytes,
-            INT_MAX,
-            SIZE_MAX,
+            pylong_asnativebytes_too_big_n,
+            SIZE_MAX
         )
 
         # Abbreviate sizeof(Py_ssize_t) to SZ because we use it a lot
@@ -528,11 +528,11 @@ def test_long_asnativebytes(self):
             asnativebytes(1, buffer, 0, 2)
         with self.assertRaises(TypeError):
             asnativebytes('not a number', buffer, 0, -1)
+
+        # We pass any number we like, but the function will pass an n_bytes
+        # that is too big to make sure we fail
         with self.assertRaises(SystemError):
-            # n_bytes is taken as size_t and clamped to 'int'. With the sign
-            # change, we should always be able to pass INT_MAX+1 and see this
-            # failure.
-            asnativebytes(1, buffer, INT_MAX + 1, -1)
+            pylong_asnativebytes_too_big_n(100)
 
     def test_long_fromnativebytes(self):
         import math

Modules/_testcapi/long.c

@@ -802,6 +802,13 @@ pylong_asnativebytes(PyObject *module, PyObject *args)
     return res >= 0 ? PyLong_FromLong(res) : NULL;
 }
 
+static PyObject *
+pylong_asnativebytes_too_big_n(PyObject *module, PyObject *v)
+{
+    int res = PyLong_AsNativeBytes(v, NULL, (size_t)INT_MAX + 1, -1);
+    return res >= 0 ? PyLong_FromLong(res) : NULL;
+}
+
 static PyObject *
 pylong_fromnativebytes(PyObject *module, PyObject *args)
 {
@@ -852,6 +859,7 @@ static PyMethodDef test_methods[] = {
     {"pylong_asdouble",             pylong_asdouble,            METH_O},
     {"pylong_asvoidptr",            pylong_asvoidptr,           METH_O},
     {"pylong_asnativebytes",        pylong_asnativebytes,       METH_VARARGS},
+    {"pylong_asnativebytes_too_big_n", pylong_asnativebytes_too_big_n, METH_O},
     {"pylong_fromnativebytes",      pylong_fromnativebytes,     METH_VARARGS},
     {NULL},
 };