gh-108444: Add PyLong_AsInt() public function

* Rename _PyLong_AsInt() to PyLong_AsInt().
* Add documentation.
* Add test.
* For now, keep _PyLong_AsInt() as an alias to PyLong_AsInt().

Author: vstinner

Doc/c-api/long.rst

@@ -136,6 +136,14 @@ distinguished from a number.  Use :c:func:`PyErr_Occurred` to disambiguate.
       This function will no longer use :meth:`~object.__int__`.
 
 
+.. c:function:: int PyLong_AsInt(PyObject *obj)
+
+   Similar to :c:func:`PyLong_AsLong`, but store the result in a C
+   :c:expr:`int` instead of a C :c:expr:`long`.
+
+   .. versionadded:: 3.13
+
+
 .. c:function:: long PyLong_AsLongAndOverflow(PyObject *obj, int *overflow)
 
    Return a C :c:expr:`long` representation of *obj*.  If *obj* is not an

Doc/data/stable_abi.dat

@@ -871,6 +871,12 @@ New Features
   :term:`shutting down <interpreter shutdown>`.
   (Contributed by Victor Stinner in :gh:`108014`.)
 
+* Add :c:func:`PyLong_AsInt` function: similar to :c:func:`PyLong_AsLong`, but
+  store the result in a C :c:expr:`int` instead of a C :c:expr:`long`.
+  Previously, it was known as the the private function :c:func:`!_PyLong_AsInt`
+  (with an underscore prefix).
+  (Contributed by Victor Stinner in :gh:`108014`.)
+
 Porting to Python 3.13
 ----------------------
 

Doc/whatsnew/3.13.rst

@@ -2,7 +2,8 @@
 #  error "this header file must not be included directly"
 #endif
 
-PyAPI_FUNC(int) _PyLong_AsInt(PyObject *);
+// Alias for backport compatibility
+#define _PyLong_AsInt PyLong_AsInt
 
 PyAPI_FUNC(int) _PyLong_UnsignedShort_Converter(PyObject *, void *);
 PyAPI_FUNC(int) _PyLong_UnsignedInt_Converter(PyObject *, void *);

Include/cpython/longobject.h

@@ -18,12 +18,18 @@ PyAPI_FUNC(PyObject *) PyLong_FromUnsignedLong(unsigned long);
 PyAPI_FUNC(PyObject *) PyLong_FromSize_t(size_t);
 PyAPI_FUNC(PyObject *) PyLong_FromSsize_t(Py_ssize_t);
 PyAPI_FUNC(PyObject *) PyLong_FromDouble(double);
+
 PyAPI_FUNC(long) PyLong_AsLong(PyObject *);
 PyAPI_FUNC(long) PyLong_AsLongAndOverflow(PyObject *, int *);
 PyAPI_FUNC(Py_ssize_t) PyLong_AsSsize_t(PyObject *);
 PyAPI_FUNC(size_t) PyLong_AsSize_t(PyObject *);
 PyAPI_FUNC(unsigned long) PyLong_AsUnsignedLong(PyObject *);
 PyAPI_FUNC(unsigned long) PyLong_AsUnsignedLongMask(PyObject *);
+
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030d0000
+PyAPI_FUNC(int) PyLong_AsInt(PyObject *);
+#endif
+
 PyAPI_FUNC(PyObject *) PyLong_GetInfo(void);
 
 /* It may be useful in the future. I've added it in the PyInt -> PyLong

Include/longobject.h

@@ -34,6 +34,28 @@ def test_compact_known(self):
         self.assertEqual(_testcapi.call_long_compact_api(sys.maxsize),
                          (False, -1))
 
+    def test_long_asint(self):
+        PyLong_AsInt = _testcapi.PyLong_AsInt
+        INT_MIN = _testcapi.INT_MIN
+        INT_MAX = _testcapi.INT_MAX
+
+        # round trip (object -> int -> object)
+        for value in (INT_MIN, INT_MAX, -1, 0, 1, 123):
+            with self.subTest(value=value):
+                self.assertEqual(PyLong_AsInt(value), value)
+
+        # bound checking
+        with self.assertRaises(OverflowError):
+            PyLong_AsInt(INT_MIN - 1)
+        with self.assertRaises(OverflowError):
+            PyLong_AsInt(INT_MAX + 1)
+
+        # invalid type
+        for value in (1.0, b'2', '3'):
+            with self.subTest(value=value):
+                with self.assertRaises(TypeError):
+                    PyLong_AsInt(value)
+
 
 if __name__ == "__main__":
     unittest.main()

Lib/test/test_capi/test_long.py

@@ -0,0 +1,4 @@
+Add :c:func:`PyLong_AsInt` function: similar to :c:func:`PyLong_AsLong`, but
+store the result in a C :c:expr:`int` instead of a C :c:expr:`long`.
+Previously, it was known as the the private function :c:func:`!_PyLong_AsInt`
+(with an underscore prefix). Patch by by Victor Stinner.

Lib/test/test_stable_abi_ctypes.py

@@ -2450,3 +2450,5 @@
     added = '3.13'
 [function.PyDict_GetItemStringRef]
     added = '3.13'
+[function.PyLong_AsInt]
+    added = '3.13'