python
@@ -13,6 +13,24 @@ extern int _PyArg_NoKwnames(const char *funcname, PyObject *kwnames);
 #define _PyArg_NoKwnames(funcname, kwnames) \
     ((kwnames) == NULL || _PyArg_NoKwnames((funcname), (kwnames)))
 
+// Export for '_bz2' shared extension
+PyAPI_FUNC(int) _PyArg_NoPositional(const char *funcname, PyObject *args);
+#define _PyArg_NoPositional(funcname, args) \
+    ((args) == NULL || _PyArg_NoPositional((funcname), (args)))
+
+// Export for '_asyncio' shared extension
+PyAPI_FUNC(int) _PyArg_NoKeywords(const char *funcname, PyObject *kwargs);
+#define _PyArg_NoKeywords(funcname, kwargs) \
+    ((kwargs) == NULL || _PyArg_NoKeywords((funcname), (kwargs)))
+
+// Export for 'zlib' shared extension
+PyAPI_FUNC(int) _PyArg_CheckPositional(const char *, Py_ssize_t,
+                                       Py_ssize_t, Py_ssize_t);
+#define _Py_ANY_VARARGS(n) ((n) == PY_SSIZE_T_MAX)
+#define _PyArg_CheckPositional(funcname, nargs, min, max) \
+    ((!_Py_ANY_VARARGS(max) && (min) <= (nargs) && (nargs) <= (max)) \
+     || _PyArg_CheckPositional((funcname), (nargs), (min), (max)))
+
 extern PyObject ** _Py_VaBuildStack(
     PyObject **small_stack,
     Py_ssize_t small_stack_len,
@@ -22,6 +40,80 @@ extern PyObject ** _Py_VaBuildStack(
 
 extern PyObject* _PyModule_CreateInitialized(PyModuleDef*, int apiver);
 
+// Export for '_curses' shared extension
+PyAPI_FUNC(int) _PyArg_ParseStack(
+    PyObject *const *args,
+    Py_ssize_t nargs,
+    const char *format,
+    ...);
+
+extern int _PyArg_UnpackStack(
+    PyObject *const *args,
+    Py_ssize_t nargs,
+    const char *name,
+    Py_ssize_t min,
+    Py_ssize_t max,
+    ...);
+
+// Export for '_heapq' shared extension
+PyAPI_FUNC(void) _PyArg_BadArgument(
+    const char *fname,
+    const char *displayname,
+    const char *expected,
+    PyObject *arg);
+
+// --- _PyArg_Parser API ---------------------------------------------------
+
+typedef struct _PyArg_Parser {
+    int initialized;
+    const char *format;
+    const char * const *keywords;
+    const char *fname;
+    const char *custom_msg;
+    int pos;            /* number of positional-only arguments */
+    int min;            /* minimal number of arguments */
+    int max;            /* maximal number of positional arguments */
+    PyObject *kwtuple;  /* tuple of keyword parameter names */
+    struct _PyArg_Parser *next;
+} _PyArg_Parser;
+
+// Export for '_testclinic' shared extension
+PyAPI_FUNC(int) _PyArg_ParseTupleAndKeywordsFast(PyObject *, PyObject *,
+                                                 struct _PyArg_Parser *, ...);
+
+// Export for '_dbm' shared extension
+PyAPI_FUNC(int) _PyArg_ParseStackAndKeywords(
+    PyObject *const *args,
+    Py_ssize_t nargs,
+    PyObject *kwnames,
+    struct _PyArg_Parser *,
+    ...);
+
+// Export for 'math' shared extension
+PyAPI_FUNC(PyObject * const *) _PyArg_UnpackKeywords(
+    PyObject *const *args,
+    Py_ssize_t nargs,
+    PyObject *kwargs,
+    PyObject *kwnames,
+    struct _PyArg_Parser *parser,
+    int minpos,
+    int maxpos,
+    int minkw,
+    PyObject **buf);
+#define _PyArg_UnpackKeywords(args, nargs, kwargs, kwnames, parser, minpos, maxpos, minkw, buf) \
+    (((minkw) == 0 && (kwargs) == NULL && (kwnames) == NULL && \
+      (minpos) <= (nargs) && (nargs) <= (maxpos) && (args) != NULL) ? (args) : \
+     _PyArg_UnpackKeywords((args), (nargs), (kwargs), (kwnames), (parser), \
+                           (minpos), (maxpos), (minkw), (buf)))
+
+// Export for '_testclinic' shared extension
+PyAPI_FUNC(PyObject * const *) _PyArg_UnpackKeywordsWithVararg(
+        PyObject *const *args, Py_ssize_t nargs,
+        PyObject *kwargs, PyObject *kwnames,
+        struct _PyArg_Parser *parser,
+        int minpos, int maxpos, int minkw,
+        int vararg, PyObject **buf);
+
 #ifdef __cplusplus
 }
 #endif

@@ -134,12 +134,6 @@ PyAPI_FUNC(PyObject *) PyModule_FromDefAndSpec2(PyModuleDef *def,
 
 #endif /* New in 3.5 */
 
-#ifndef Py_LIMITED_API
-#  define Py_CPYTHON_MODSUPPORT_H
-#  include "cpython/modsupport.h"
-#  undef Py_CPYTHON_MODSUPPORT_H
-#endif
-
 #ifdef __cplusplus
 }
 #endif

@@ -1720,7 +1720,6 @@ PYTHON_HEADERS= \
 		$(srcdir)/Include/cpython/longobject.h \
 		$(srcdir)/Include/cpython/memoryobject.h \
 		$(srcdir)/Include/cpython/methodobject.h \
-		$(srcdir)/Include/cpython/modsupport.h \
 		$(srcdir)/Include/cpython/object.h \
 		$(srcdir)/Include/cpython/objimpl.h \
 		$(srcdir)/Include/cpython/odictobject.h \

diff --git a/Misc/NEWS.d/next/C API/2023-10-17-10-21-59.gh-issue-110964.OxqEjd.rst b/Misc/NEWS.d/next/C API/2023-10-17-10-21-59.gh-issue-110964.OxqEjd.rst
@@ -0,0 +1,2 @@
+Move the undocumented private _PyArg functions and _PyArg_Parser structure
+to internal C API (``pycore_modsupport.h``). Patch by Victor Stinner.
@@ -4,6 +4,7 @@
 
 #include "Python.h"
 #include "pycore_dict.h"          // _PyDict_GetItem_KnownHash()
+#include "pycore_modsupport.h"    // _PyArg_CheckPositional()
 #include "pycore_moduleobject.h"  // _PyModule_GetState()
 #include "pycore_pyerrors.h"      // _PyErr_ClearExcState()
 #include "pycore_pylifecycle.h"   // _Py_IsInterpreterFinalizing()

diff --git a/Modules/_blake2/clinic/blake2b_impl.c.h b/Modules/_blake2/clinic/blake2b_impl.c.h
diff --git a/Modules/_blake2/clinic/blake2s_impl.c.h b/Modules/_blake2/clinic/blake2s_impl.c.h
diff --git a/Modules/_csv.c b/Modules/_csv.c
@@ -10,6 +10,11 @@ module instead.
 
 #define MODULE_VERSION "1.0"
 
+// clinic/_csv.c.h uses internal pycore_modsupport.h API
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
 #include "Python.h"
 
 #include <stddef.h>               // offsetof()

diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
@@ -110,6 +110,9 @@ bytes(cdata)
 
 #include "pycore_call.h"          // _PyObject_CallNoArgs()
 #include "pycore_ceval.h"         // _Py_EnterRecursiveCall()
+#ifdef MS_WIN32
+#  include "pycore_modsupport.h"  // _PyArg_NoKeywords()
+#endif
 #include "pycore_pyerrors.h"      // _PyErr_WriteUnraisableMsg()
 
 

diff --git a/Modules/_curses_panel.c b/Modules/_curses_panel.c
@@ -10,6 +10,11 @@ static const char PyCursesVersion[] = "2.1";
 
 /* Includes */
 
+// clinic/_curses_panel.c.h uses internal pycore_modsupport.h API
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
 #include "Python.h"
 
 #include "py_curses.h"

@@ -2,6 +2,11 @@
 /* DBM module using dictionary interface */
 
 
+// clinic/_dbmmodule.c.h uses internal pycore_modsupport.h API
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
 #include "Python.h"
 
 #include <sys/types.h>

@@ -1,8 +1,12 @@
-
 /* GDBM module using dictionary interface */
 /* Author: Anthony Baxter, after dbmmodule.c */
 /* Doc strings: Mitch Chapman */
 
+// clinic/_gdbmmodule.c.h uses internal pycore_modsupport.h API
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
 #include "Python.h"
 #include "gdbm.h"
 

diff --git a/Modules/_io/clinic/_iomodule.c.h b/Modules/_io/clinic/_iomodule.c.h
diff --git a/Modules/_io/clinic/bufferedio.c.h b/Modules/_io/clinic/bufferedio.c.h
diff --git a/Modules/_io/clinic/bytesio.c.h b/Modules/_io/clinic/bytesio.c.h
diff --git a/Modules/_io/clinic/fileio.c.h b/Modules/_io/clinic/fileio.c.h
diff --git a/Modules/_io/clinic/iobase.c.h b/Modules/_io/clinic/iobase.c.h
diff --git a/Modules/_io/clinic/stringio.c.h b/Modules/_io/clinic/stringio.c.h
diff --git a/Modules/_io/clinic/textio.c.h b/Modules/_io/clinic/textio.c.h
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Move the undocumented private _PyArg functions and _PyArg_Parser structure
		to internal C API (``pycore_modsupport.h``). Patch by Victor Stinner.