Make PY_SSIZE_T_CLEAN not mandatory.

Include/abstract.h

@@ -135,10 +135,8 @@ extern "C" {
    This function always succeeds. */
 
 
-#ifdef PY_SSIZE_T_CLEAN
-#  define PyObject_CallFunction _PyObject_CallFunction_SizeT
-#  define PyObject_CallMethod _PyObject_CallMethod_SizeT
-#endif
+#define PyObject_CallFunction _PyObject_CallFunction_SizeT
+#define PyObject_CallMethod _PyObject_CallMethod_SizeT
 
 
 #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03090000

Include/cpython/abstract.h

@@ -4,9 +4,7 @@
 
 /* === Object Protocol ================================================== */
 
-#ifdef PY_SSIZE_T_CLEAN
-#  define _PyObject_CallMethodId _PyObject_CallMethodId_SizeT
-#endif
+#define _PyObject_CallMethodId _PyObject_CallMethodId_SizeT
 
 /* Convert keyword arguments from the FASTCALL (stack: C array, kwnames: tuple)
    format to a Python dictionary ("kwargs" dict).

Include/cpython/modsupport.h

@@ -2,19 +2,9 @@
 #  error "this header file must not be included directly"
 #endif
 
-/* If PY_SSIZE_T_CLEAN is defined, each functions treats #-specifier
-   to mean Py_ssize_t */
-#ifdef PY_SSIZE_T_CLEAN
+/* Each functions treats #-specifier to mean Py_ssize_t
+ * regardless PY_SSIZE_T_CLEAN */
 #define _Py_VaBuildStack                _Py_VaBuildStack_SizeT
-#else
-PyAPI_FUNC(PyObject *) _Py_VaBuildValue_SizeT(const char *, va_list);
-PyAPI_FUNC(PyObject **) _Py_VaBuildStack_SizeT(
-    PyObject **small_stack,
-    Py_ssize_t small_stack_len,
-    const char *format,
-    va_list va,
-    Py_ssize_t *p_nargs);
-#endif
 
 PyAPI_FUNC(int) _PyArg_UnpackStack(
     PyObject *const *args,
@@ -63,12 +53,10 @@ typedef struct _PyArg_Parser {
     struct _PyArg_Parser *next;
 } _PyArg_Parser;
 
-#ifdef PY_SSIZE_T_CLEAN
 #define _PyArg_ParseTupleAndKeywordsFast  _PyArg_ParseTupleAndKeywordsFast_SizeT
 #define _PyArg_ParseStack  _PyArg_ParseStack_SizeT
 #define _PyArg_ParseStackAndKeywords  _PyArg_ParseStackAndKeywords_SizeT
 #define _PyArg_VaParseTupleAndKeywordsFast  _PyArg_VaParseTupleAndKeywordsFast_SizeT
-#endif
 
 PyAPI_FUNC(int) _PyArg_ParseTupleAndKeywordsFast(PyObject *, PyObject *,
                                                  struct _PyArg_Parser *, ...);

Include/modsupport.h

@@ -9,20 +9,19 @@ extern "C" {
 
 #include <stdarg.h>               // va_list
 
-/* If PY_SSIZE_T_CLEAN is defined, each functions treats #-specifier
-   to mean Py_ssize_t */
-#ifdef PY_SSIZE_T_CLEAN
+/* Since Python 3.13, each functions treats #-specifier to mean Py_ssize_t
+ * regardless PY_SSIZE_T_CLEAN is defined,
+ */
 #define PyArg_Parse                     _PyArg_Parse_SizeT
 #define PyArg_ParseTuple                _PyArg_ParseTuple_SizeT
 #define PyArg_ParseTupleAndKeywords     _PyArg_ParseTupleAndKeywords_SizeT
 #define PyArg_VaParse                   _PyArg_VaParse_SizeT
 #define PyArg_VaParseTupleAndKeywords   _PyArg_VaParseTupleAndKeywords_SizeT
 #define Py_BuildValue                   _Py_BuildValue_SizeT
 #define Py_VaBuildValue                 _Py_VaBuildValue_SizeT
-#endif
 
 /* Due to a glitch in 3.2, the _SizeT versions weren't exported from the DLL. */
-#if !defined(PY_SSIZE_T_CLEAN) || !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03030000
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03030000
 PyAPI_FUNC(int) PyArg_Parse(PyObject *, const char *, ...);
 PyAPI_FUNC(int) PyArg_ParseTuple(PyObject *, const char *, ...);
 PyAPI_FUNC(int) PyArg_ParseTupleAndKeywords(PyObject *, PyObject *,

Misc/NEWS.d/next/C API/2023-05-25-17-30-43.gh-issue-104922.V6nibW.rst

@@ -0,0 +1,2 @@
+``PY_SSIZE_T_CLEAN`` is no longer required to use '#' specifier in APIs like
+:c:func:`PyArg_ParseTuple` and :c:func:`Py_BuildValue`.

Python/getargs.c

@@ -657,7 +657,11 @@ convertsimple(PyObject *arg, const char **p_format, va_list *p_va, int flags,
               char *msgbuf, size_t bufsize, freelist_t *freelist)
 {
 #define RETURN_ERR_OCCURRED return msgbuf
-    /* For # codes */
+    // For # codes
+    // Even though Python 3.13 uses ssize_t ragardless PY_SSIZE_T_CLEAN,
+    // extension compiled with Python ~3.9 may still use int version API.
+    // Remove this check after we drop supporting extension module built with
+    // Python ~3.9.
 #define REQUIRE_PY_SSIZE_T_CLEAN \
     if (!(flags & FLAG_SIZE_T)) { \
         PyErr_SetString(PyExc_SystemError, \

Python/modsupport.c

@@ -277,6 +277,10 @@ do_mktuple(const char **p_format, va_list *p_va, char endchar, Py_ssize_t n, int
 static PyObject *
 do_mkvalue(const char **p_format, va_list *p_va, int flags)
 {
+    // Even though Python 3.13 uses ssize_t ragardless PY_SSIZE_T_CLEAN,
+    // extension compiled with Python ~3.9 may still use int version API.
+    // Remove this check after we drop supporting extension module built with
+    // Python ~3.9.
 #define ERROR_NEED_PY_SSIZE_T_CLEAN \
     { \
         PyErr_SetString(PyExc_SystemError, \