gh-127937: deprecate _PyLong_FromDigits() function

Author: skirpichev

Doc/deprecations/c-api-pending-removal-in-future.rst

@@ -35,6 +35,8 @@ although there is currently no date scheduled for their removal.
 * :c:member:`!PyBytesObject.ob_shash` member:
   call :c:func:`PyObject_Hash` instead.
 * :c:member:`!PyDictObject.ma_version_tag` member.
+* :c:func::c:func:`!_PyLong_FromDigits`
+  Use instead :c:struct:`PyLongWriter` API.
 * Thread Local Storage (TLS) API:
 
   * :c:func:`PyThread_create_key`:

Include/cpython/longintrepr.h

@@ -105,7 +105,7 @@ PyAPI_FUNC(PyLongObject*) _PyLong_New(Py_ssize_t);
 // Return a copy of src.
 PyAPI_FUNC(PyObject*) _PyLong_Copy(PyLongObject *src);
 
-PyAPI_FUNC(PyLongObject*) _PyLong_FromDigits(
+Py_DEPRECATED(3.14) PyAPI_FUNC(PyLongObject*) _PyLong_FromDigits(
     int negative,
     Py_ssize_t digit_count,
     digit *digits);

Misc/NEWS.d/next/C_API/2024-12-14-10-14-27.gh-issue-127937.-tT1KP.rst

@@ -0,0 +1,2 @@
+Deprecate the :c:func:`!_PyLong_FromDigits`, use instead
+:c:struct:`PyLongWriter` API.  Patch by Sergey B Kirpichev.