gh-138712: Add os.NODEV

Author: serhiy-storchaka

Doc/library/os.rst

@@ -2630,6 +2630,11 @@ features:
    Compose a raw device number from the major and minor device numbers.
 
 
+.. data:: NODEV
+
+   Non-existent device.
+
+
 .. function:: pathconf(path, name)
 
    Return system configuration information relevant to a named file. *name*

Lib/test/test_posix.py

@@ -757,12 +757,24 @@ def test_makedev(self):
             self.assertRaises((ValueError, OverflowError), posix.makedev, x, minor)
             self.assertRaises((ValueError, OverflowError), posix.makedev, major, x)
 
-        if sys.platform == 'linux' and not support.linked_to_musl():
-            NODEV = -1
+        if (hasattr(posix, 'NODEV') and
+            sys.platform.startswith('linux', 'macos', 'freebsd', 'dragonfly',
+                                    'sunos')):
+            NODEV = posix.NODEV
             self.assertEqual(posix.major(NODEV), NODEV)
             self.assertEqual(posix.minor(NODEV), NODEV)
             self.assertEqual(posix.makedev(NODEV, NODEV), NODEV)
 
+    def test_nodev(self):
+        if not hasattr(posix, 'NODEV'):
+            if (not sys.platform.startswith('linux', 'macos', 'freebsd',
+                                            'dragonfly',
+                                            'netbsd', 'openbsd', 'sunos') or
+                support.linked_to_musl()):
+                self.skipTest('not defined on this platform')
+        self.assertHasAttr(posix, 'NODEV')
+        self.assertEqual(posix.NODEV, -1)
+
     def _test_all_chown_common(self, chown_func, first_param, stat_func):
         """Common code for chown, fchown and lchown tests."""
         def check_stat(uid, gid):

Misc/NEWS.d/next/Library/2025-09-10-10-11-59.gh-issue-138712.avrPG5.rst

@@ -0,0 +1 @@
+Add :const:`os.NODEV`.

Modules/posixmodule.c

@@ -2759,7 +2759,7 @@ _pystat_fromstructstat(PyObject *module, STRUCT_STAT *st)
     SET_ITEM(ST_BLOCKS_IDX, PyLong_FromLong((long)st->st_blocks));
 #endif
 #ifdef HAVE_STRUCT_STAT_ST_RDEV
-    SET_ITEM(ST_RDEV_IDX, PyLong_FromLong((long)st->st_rdev));
+    SET_ITEM(ST_RDEV_IDX, _PyLong_FromDev(st->st_rdev));
 #endif
 #ifdef HAVE_STRUCT_STAT_ST_GEN
     SET_ITEM(ST_GEN_IDX, PyLong_FromLong((long)st->st_gen));
@@ -17878,6 +17878,10 @@ all_ins(PyObject *m)
 #endif
 #endif  /* HAVE_EVENTFD && EFD_CLOEXEC */
 
+#ifdef NODEV
+    if (PyModule_Add(m, _PyLong_FromDev(NODEV))) return -1;
+#endif
+
 #if defined(__APPLE__)
     if (PyModule_AddIntConstant(m, "_COPYFILE_DATA", COPYFILE_DATA)) return -1;
     if (PyModule_AddIntConstant(m, "_COPYFILE_STAT", COPYFILE_STAT)) return -1;