python
@@ -938,8 +938,9 @@ Build Changes
   library, GCC built-in atomic functions, or MSVC interlocked intrinsics.
 
 * The ``errno``, ``md5``, ``resource``, ``winsound``, ``_ctypes_test``,
-  ``_scproxy``, ``_stat``, ``_testimportmultiple`` and ``_uuid`` C extensions
-  are now built with the :ref:`limited C API <limited-c-api>`.
+  ``_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`.)
 
 

diff --git a/Misc/NEWS.d/next/Build/2023-10-17-01-56-11.gh-issue-85283.V156T2.rst b/Misc/NEWS.d/next/Build/2023-10-17-01-56-11.gh-issue-85283.V156T2.rst
@@ -1,4 +1,5 @@
 The ``errno``, ``md5``, ``resource``, ``winsound``, ``_ctypes_test``,
-``_scproxy``, ``_stat``, ``_testimportmultiple`` and ``_uuid`` C extensions are
-now built with the :ref:`limited C API <limited-c-api>`.
+``_multiprocessing.posixshmem``, ``_scproxy``, ``_stat``,
+``_testimportmultiple`` and ``_uuid`` C extensions are now built with the
+:ref:`limited C API <limited-c-api>`.
 Patch by Victor Stinner.
diff --git a/Modules/_multiprocessing/clinic/posixshmem.c.h b/Modules/_multiprocessing/clinic/posixshmem.c.h
@@ -2,18 +2,17 @@
 posixshmem - A Python extension that provides shm_open() and shm_unlink()
 */
 
-// clinic/posixshmem.c.h uses internal pycore_modsupport.h API
-#ifndef Py_BUILD_CORE_BUILTIN
-#  define Py_BUILD_CORE_MODULE 1
-#endif
+// Need limited C API version 3.13 for Py_MOD_PER_INTERPRETER_GIL_SUPPORTED
+#define Py_LIMITED_API 0x030d0000
 
 #include <Python.h>
 
-// for shm_open() and shm_unlink()
+#include <errno.h>                // EINTR
 #ifdef HAVE_SYS_MMAN_H
-#include <sys/mman.h>
+#  include <sys/mman.h>           // shm_open(), shm_unlink()
 #endif
 
+
 /*[clinic input]
 module _posixshmem
 [clinic start generated code]*/
@@ -45,7 +44,7 @@ _posixshmem_shm_open_impl(PyObject *module, PyObject *path, int flags,
 {
     int fd;
     int async_err = 0;
-    const char *name = PyUnicode_AsUTF8(path);
+    const char *name = PyUnicode_AsUTF8AndSize(path, NULL);
     if (name == NULL) {
         return -1;
     }
@@ -84,7 +83,7 @@ _posixshmem_shm_unlink_impl(PyObject *module, PyObject *path)
 {
     int rv;
     int async_err = 0;
-    const char *name = PyUnicode_AsUTF8(path);
+    const char *name = PyUnicode_AsUTF8AndSize(path, NULL);
     if (name == NULL) {
         return NULL;
     }