pythongh-85283: Build fcntl extension with the limited C API (python#…

…116791)

Doc/whatsnew/3.13.rst

@@ -1460,8 +1460,8 @@ Build Changes
 * Building CPython now requires a compiler with support for the C11 atomic
   library, GCC built-in atomic functions, or MSVC interlocked intrinsics.
 
-* The ``errno``, ``md5``, ``resource``, ``winsound``, ``_ctypes_test``,
-  ``_multiprocessing.posixshmem``, ``_scproxy``, ``_stat``,
+* The ``errno``, ``fcntl``, ``grp``, ``md5``, ``resource``, ``winsound``,
+  ``_ctypes_test``, ``_multiprocessing.posixshmem``, ``_scproxy``, ``_stat``,
   ``_testimportmultiple`` and ``_uuid`` C extensions are now built with the
   :ref:`limited C API <limited-c-api>`.
   (Contributed by Victor Stinner in :gh:`85283`.)

Misc/NEWS.d/next/C API/2024-03-14-10-33-58.gh-issue-85283.LOgmdU.rst

@@ -0,0 +1,2 @@
+The ``fcntl`` and ``grp`` C extensions are now built with the :ref:`limited
+C API <limited-c-api>`. (Contributed by Victor Stinner in :gh:`85283`.)

Modules/fcntlmodule.c

@@ -1,22 +1,25 @@
 /* fcntl module */
 
-#ifndef Py_BUILD_CORE_BUILTIN
-#  define Py_BUILD_CORE_MODULE 1
+// Need limited C API version 3.13 for PyLong_AsInt()
+#include "pyconfig.h"   // Py_GIL_DISABLED
+#ifndef Py_GIL_DISABLED
+#  define Py_LIMITED_API 0x030d0000
 #endif
 
 #include "Python.h"
 
+#include <errno.h>                // EINTR
+#include <fcntl.h>                // fcntl()
+#include <string.h>               // memcpy()
+#include <sys/ioctl.h>            // ioctl()
 #ifdef HAVE_SYS_FILE_H
-#include <sys/file.h>
+#  include <sys/file.h>           // flock()
 #endif
 #ifdef HAVE_LINUX_FS_H
-#include <linux/fs.h>
+#  include <linux/fs.h>
 #endif
-
-#include <sys/ioctl.h>
-#include <fcntl.h>
 #ifdef HAVE_STROPTS_H
-#include <stropts.h>
+#  include <stropts.h>            // I_FLUSHBAND
 #endif
 
 /*[clinic input]