gh-138859: Account for ParamSpec defaults that are not lists … (#138868)

stx_atomic_write_unit_max_opt was added in Linux 6.16, but is controlled
by the STATX_WRITE_ATOMIC mask bit added in Linux 6.11.  That's safe at
runtime because all kernels clear the reserved space in struct statx and
zero is a valid value for stx_atomic_write_unit_max_opt, and it avoids
allocating another mask bit, which are a limited resource.  But it also
means the kernel headers don't provide a way to check whether
stx_atomic_write_unit_max_opt exists, so add a configure check.

Doc/library/os.rst

@@ -3496,7 +3496,7 @@ features:
       Maximum optimized size for direct I/O with torn-write protection.
 
       .. availability:: Linux >= 4.11 with glibc >= 2.28 and build-time kernel
-         userspace API headers >= 6.11.
+         userspace API headers >= 6.16.
 
    .. attribute:: stx_atomic_write_segments_max
 

Lib/test/test_os/test_os.py

@@ -164,6 +164,20 @@ def test_getcwdb(self):
         self.assertIsInstance(cwd, bytes)
         self.assertEqual(os.fsdecode(cwd), os.getcwd())
 
+    def test_type_fqdn(self):
+        def fqdn(obj):
+            return (obj.__module__, obj.__qualname__)
+
+        native = os.name
+        self.assertEqual(fqdn(os.stat_result), ("os", "stat_result"))
+        self.assertEqual(fqdn(os.times_result), (native, "times_result"))
+        if hasattr(os, "statvfs_result"):
+            self.assertEqual(fqdn(os.statvfs_result), ("os", "statvfs_result"))
+        if hasattr(os, "sched_param"):
+            self.assertEqual(fqdn(os.sched_param), (native, "sched_param"))
+        if hasattr(os, "waitid_result"):
+            self.assertEqual(fqdn(os.waitid_result), (native, "waitid_result"))
+
 
 # Tests creating TESTFN
 class FileTests(unittest.TestCase):

Lib/test/test_site.py

@@ -855,12 +855,15 @@ def get_excepted_output(self, *args):
             return 10, None
 
     def invoke_command_line(self, *args):
-        args = ["-m", "site", *args]
+        cmd_args = []
+        if sys.flags.no_user_site:
+            cmd_args.append("-s")
+        cmd_args.extend(["-m", "site", *args])
 
         with EnvironmentVarGuard() as env:
             env["PYTHONUTF8"] = "1"
             env["PYTHONIOENCODING"] = "utf-8"
-            proc = spawn_python(*args, text=True, env=env,
+            proc = spawn_python(*cmd_args, text=True, env=env,
                                 encoding='utf-8', errors='replace')
 
         output = kill_python(proc)

Lib/test/test_typing.py

@@ -762,6 +762,16 @@ class A(Generic[T, P, U]): ...
         self.assertEqual(A[float, [range]].__args__, (float, (range,), float))
         self.assertEqual(A[float, [range], int].__args__, (float, (range,), int))
 
+    def test_paramspec_and_typevar_specialization_2(self):
+        T = TypeVar("T")
+        P = ParamSpec('P', default=...)
+        U = TypeVar("U", default=float)
+        self.assertEqual(P.__default__, ...)
+        class A(Generic[T, P, U]): ...
+        self.assertEqual(A[float].__args__, (float, ..., float))
+        self.assertEqual(A[float, [range]].__args__, (float, (range,), float))
+        self.assertEqual(A[float, [range], int].__args__, (float, (range,), int))
+
     def test_typevartuple_none(self):
         U = TypeVarTuple('U')
         U_None = TypeVarTuple('U_None', default=None)

Lib/typing.py

@@ -1113,7 +1113,7 @@ def _paramspec_prepare_subst(self, alias, args):
     params = alias.__parameters__
     i = params.index(self)
     if i == len(args) and self.has_default():
-        args = [*args, self.__default__]
+        args = (*args, self.__default__)
     if i >= len(args):
         raise TypeError(f"Too few arguments for {alias}")
     # Special case where Z[[int, str, bool]] == Z[int, str, bool] in PEP 612.

Misc/NEWS.d/next/Library/2025-09-13-12-19-17.gh-issue-138859.PxjIoN.rst

@@ -0,0 +1 @@
+Fix generic type parameterization raising a :exc:`TypeError` when omitting a :class:`ParamSpec` that has a default which is not a list of types.

Modules/_localemodule.c

@@ -455,35 +455,23 @@ _locale_strxfrm_impl(PyObject *module, PyObject *str)
         goto exit;
     }
 
-    /* assume no change in size, first */
-    n1 = n1 + 1;
-    /* Yet another +1 is needed to work around a platform bug in wcsxfrm()
-     * on macOS. See gh-130567. */
-    buf = PyMem_New(wchar_t, n1+1);
-    if (!buf) {
-        PyErr_NoMemory();
-        goto exit;
-    }
     errno = 0;
-    n2 = wcsxfrm(buf, s, n1);
+    n2 = wcsxfrm(NULL, s, 0);
     if (errno && errno != ERANGE) {
         PyErr_SetFromErrno(PyExc_OSError);
         goto exit;
     }
-    if (n2 >= (size_t)n1) {
-        /* more space needed */
-        wchar_t * new_buf = PyMem_Realloc(buf, (n2+1)*sizeof(wchar_t));
-        if (!new_buf) {
-            PyErr_NoMemory();
-            goto exit;
-        }
-        buf = new_buf;
-        errno = 0;
-        n2 = wcsxfrm(buf, s, n2+1);
-        if (errno) {
-            PyErr_SetFromErrno(PyExc_OSError);
-            goto exit;
-        }
+    buf = PyMem_New(wchar_t, n2+1);
+    if (!buf) {
+        PyErr_NoMemory();
+        goto exit;
+    }
+
+    errno = 0;
+    n2 = wcsxfrm(buf, s, n2+1);
+    if (errno) {
+        PyErr_SetFromErrno(PyExc_OSError);
+        goto exit;
     }
     /* The result is just a sequence of integers, they are not necessary
        Unicode code points, so PyUnicode_FromWideChar() cannot be used

Modules/posixmodule.c

@@ -2471,7 +2471,7 @@ static PyStructSequence_Field stat_result_fields[] = {
 #endif
 
 static PyStructSequence_Desc stat_result_desc = {
-    "stat_result", /* name */
+    "os.stat_result", /* name; see issue gh-63408 */
     stat_result__doc__, /* doc */
     stat_result_fields,
     10
@@ -2501,7 +2501,7 @@ static PyStructSequence_Field statvfs_result_fields[] = {
 };
 
 static PyStructSequence_Desc statvfs_result_desc = {
-    "statvfs_result", /* name */
+    "os.statvfs_result", /* name; see issue gh-63408 */
     statvfs_result__doc__, /* doc */
     statvfs_result_fields,
     10
@@ -2526,7 +2526,7 @@ static PyStructSequence_Field waitid_result_fields[] = {
 };
 
 static PyStructSequence_Desc waitid_result_desc = {
-    "waitid_result", /* name */
+    MODNAME ".waitid_result", /* name */
     waitid_result__doc__, /* doc */
     waitid_result_fields,
     5
@@ -3369,7 +3369,7 @@ static PyMemberDef pystatx_result_members[] = {
     MM(stx_atomic_write_segments_max, Py_T_UINT, atomic_write_segments_max,
         "maximum iovecs for direct I/O with torn-write protection"),
 #endif
-#if 0
+#ifdef HAVE_STRUCT_STATX_STX_ATOMIC_WRITE_UNIT_MAX_OPT
     MM(stx_atomic_write_unit_max_opt, Py_T_UINT, atomic_write_unit_max_opt,
         "maximum optimized size for direct I/O with torn-write protection"),
 #endif
@@ -8663,7 +8663,7 @@ static PyStructSequence_Field sched_param_fields[] = {
 };
 
 static PyStructSequence_Desc sched_param_desc = {
-    "sched_param", /* name */
+    MODNAME ".sched_param", /* name */
     os_sched_param__doc__, /* doc */
     sched_param_fields,
     1
@@ -11057,7 +11057,7 @@ and elapsed.\n\
 See os.times for more information.");
 
 static PyStructSequence_Desc times_result_desc = {
-    "times_result", /* name */
+    MODNAME ".times_result", /* name */
     times_result__doc__, /* doc */
     times_result_fields,
     5
@@ -18584,14 +18584,12 @@ posixmodule_exec(PyObject *m)
     }
 
 #if defined(HAVE_WAITID)
-    waitid_result_desc.name = MODNAME ".waitid_result";
     state->WaitidResultType = (PyObject *)PyStructSequence_NewType(&waitid_result_desc);
     if (PyModule_AddObjectRef(m, "waitid_result", state->WaitidResultType) < 0) {
         return -1;
     }
 #endif
 
-    stat_result_desc.name = "os.stat_result"; /* see issue #19209 */
     stat_result_desc.fields[7].name = PyStructSequence_UnnamedField;
     stat_result_desc.fields[8].name = PyStructSequence_UnnamedField;
     stat_result_desc.fields[9].name = PyStructSequence_UnnamedField;
@@ -18602,14 +18600,12 @@ posixmodule_exec(PyObject *m)
     state->statresult_new_orig = ((PyTypeObject *)state->StatResultType)->tp_new;
     ((PyTypeObject *)state->StatResultType)->tp_new = statresult_new;
 
-    statvfs_result_desc.name = "os.statvfs_result"; /* see issue #19209 */
     state->StatVFSResultType = (PyObject *)PyStructSequence_NewType(&statvfs_result_desc);
     if (PyModule_AddObjectRef(m, "statvfs_result", state->StatVFSResultType) < 0) {
         return -1;
     }
 
 #if defined(HAVE_SCHED_SETPARAM) || defined(HAVE_SCHED_SETSCHEDULER) || defined(POSIX_SPAWN_SETSCHEDULER) || defined(POSIX_SPAWN_SETSCHEDPARAM)
-    sched_param_desc.name = MODNAME ".sched_param";
     state->SchedParamType = (PyObject *)PyStructSequence_NewType(&sched_param_desc);
     if (PyModule_AddObjectRef(m, "sched_param", state->SchedParamType) < 0) {
         return -1;
@@ -18641,7 +18637,6 @@ posixmodule_exec(PyObject *m)
         return -1;
     }
 
-    times_result_desc.name = MODNAME ".times_result";
     state->TimesResultType = (PyObject *)PyStructSequence_NewType(&times_result_desc);
     if (PyModule_AddObjectRef(m, "times_result", state->TimesResultType) < 0) {
         return -1;

Objects/typevarobject.c

@@ -2123,11 +2123,6 @@ typealias_new_impl(PyTypeObject *type, PyObject *name, PyObject *value,
         return NULL;
     }
 
-    PyObject *module = caller();
-    if (module == NULL) {
-        return NULL;
-    }
-
     if (qualname == NULL || qualname == Py_None) {
         // If qualname was not set directly, we use name instead.
         qualname = name;
@@ -2138,6 +2133,11 @@ typealias_new_impl(PyTypeObject *type, PyObject *name, PyObject *value,
         }
     }
 
+    PyObject *module = caller();
+    if (module == NULL) {
+        return NULL;
+    }
+
     PyObject *ta = (PyObject *)typealias_alloc(
         name, qualname, checked_params, NULL, value, module);
     Py_DECREF(module);

configure

@@ -25133,6 +25133,21 @@ printf "%s\n" "#define HAVE_SIGINFO_T_SI_BAND 1" >>confdefs.h
 fi
 
 
+if test "$ac_cv_func_statx" = yes; then
+  # stx_atomic_write_unit_max_opt was added in Linux 6.16, but is controlled by
+  # the STATX_WRITE_ATOMIC mask bit added in Linux 6.11, so having the mask bit
+  # doesn't imply having the member.
+  ac_fn_c_check_member "$LINENO" "struct statx" "stx_atomic_write_unit_max_opt" "ac_cv_member_struct_statx_stx_atomic_write_unit_max_opt" "$ac_includes_default"
+if test "x$ac_cv_member_struct_statx_stx_atomic_write_unit_max_opt" = xyes
+then :
+
+printf "%s\n" "#define HAVE_STRUCT_STATX_STX_ATOMIC_WRITE_UNIT_MAX_OPT 1" >>confdefs.h
+
+
+fi
+
+fi
+
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for time.h that defines altzone" >&5
 printf %s "checking for time.h that defines altzone... " >&6; }
 if test ${ac_cv_header_time_altzone+y}

configure.ac

@@ -5819,6 +5819,13 @@ AC_CHECK_MEMBERS([struct passwd.pw_gecos, struct passwd.pw_passwd], [], [], [[
 # Issue #21085: In Cygwin, siginfo_t does not have si_band field.
 AC_CHECK_MEMBERS([siginfo_t.si_band], [], [], [[@%:@include <signal.h>]])
 
+if test "$ac_cv_func_statx" = yes; then
+  # stx_atomic_write_unit_max_opt was added in Linux 6.16, but is controlled by
+  # the STATX_WRITE_ATOMIC mask bit added in Linux 6.11, so having the mask bit
+  # doesn't imply having the member.
+  AC_CHECK_MEMBERS([struct statx.stx_atomic_write_unit_max_opt])
+fi
+
 AC_CACHE_CHECK([for time.h that defines altzone], [ac_cv_header_time_altzone], [
   AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[@%:@include <time.h>]], [[return altzone;]])],
     [ac_cv_header_time_altzone=yes],

pyconfig.h.in

@@ -1330,6 +1330,10 @@
 /* Define to 1 if 'pw_passwd' is a member of 'struct passwd'. */
 #undef HAVE_STRUCT_PASSWD_PW_PASSWD
 
+/* Define to 1 if 'stx_atomic_write_unit_max_opt' is a member of 'struct
+   statx'. */
+#undef HAVE_STRUCT_STATX_STX_ATOMIC_WRITE_UNIT_MAX_OPT
+
 /* Define to 1 if 'st_birthtime' is a member of 'struct stat'. */
 #undef HAVE_STRUCT_STAT_ST_BIRTHTIME