gh-108444: Add PyLong_AsInt() public function

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/whatsnew/3.13.rst

@@ -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 private function :c:func:`!_PyLong_AsInt`
+ (with an underscore prefix).
+ (Contributed by Victor Stinner in :gh:`108014`.)
+
 Porting to Python 3.13
 ----------------------
 

Include/cpython/longobject.h

@@ -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/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

Lib/test/test_capi/test_long.py

@@ -34,6 +34,36 @@ 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)
+
+ # use __index__(), not __int__()
+ class MyIndex:
+ def __index__(self):
+ return 10
+ def __int__(self):
+ return 22
+ self.assertEqual(PyLong_AsInt(MyIndex()), 10)
+
+ # 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()

Misc/NEWS.d/next/C API/2023-08-24-20-08-02.gh-issue-108014.20DOSS.rst

@@ -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 Victor Stinner.

Misc/stable_abi.toml

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

Modules/_testcapi/long.c

@@ -37,6 +37,9 @@ raise_test_long_error(const char* msg)
  return raiseTestError("test_long_api", msg);
 }
 
+// Test PyLong_FromLong()/PyLong_AsLong()
+// and PyLong_FromUnsignedLong()/PyLong_AsUnsignedLong().
+
 #define TESTNAME test_long_api_inner
 #define TYPENAME long
 #define F_S_TO_PY PyLong_FromLong
@@ -64,6 +67,9 @@ _testcapi_test_long_api_impl(PyObject *module)
 #undef F_U_TO_PY
 #undef F_PY_TO_U
 
+// Test PyLong_FromLongLong()/PyLong_AsLongLong()
+// and PyLong_FromUnsignedLongLong()/PyLong_AsUnsignedLongLong().
+
 static PyObject *
 raise_test_longlong_error(const char* msg)
 {
@@ -595,6 +601,24 @@ _testcapi_call_long_compact_api(PyObject *module, PyObject *arg)
  return Py_BuildValue("in", is_compact, value);
 }
 
+/*[clinic input]
+_testcapi.PyLong_AsInt
+ arg: object
+ /
+[clinic start generated code]*/
+
+static PyObject *
+_testcapi_PyLong_AsInt(PyObject *module, PyObject *arg)
+/*[clinic end generated code: output=0df9f19de5fa575b input=9561b97105493a67]*/
+{
+ assert(!PyErr_Occurred());
+ int value = PyLong_AsInt(arg);
+ if (value == -1 && PyErr_Occurred()){
+ return NULL;
+ }
+ return PyLong_FromLong(value);
+}
+
 static PyMethodDef test_methods[] ={
  _TESTCAPI_TEST_LONG_AND_OVERFLOW_METHODDEF
  _TESTCAPI_TEST_LONG_API_METHODDEF
@@ -605,6 +629,7 @@ static PyMethodDef test_methods[] ={
  _TESTCAPI_TEST_LONG_NUMBITS_METHODDEF
  _TESTCAPI_TEST_LONGLONG_API_METHODDEF
  _TESTCAPI_CALL_LONG_COMPACT_API_METHODDEF
+ _TESTCAPI_PYLONG_ASINT_METHODDEF
 {NULL},
 };
 

Objects/longobject.c

@@ -549,7 +549,7 @@ PyLong_AsLong(PyObject *obj)
  method. Return -1 and set an error if overflow occurs. */
 
 int
-_PyLong_AsInt(PyObject *obj)
+PyLong_AsInt(PyObject *obj)
 {
  int overflow;
  long result = PyLong_AsLongAndOverflow(obj, &overflow);