Re-introduce comment with some interesting findings on extended paths.

python · zooba · Jun 10, 2022 · Apr 24, 2022 · Apr 24, 2022 · Apr 24, 2022
commit 3f163ffadf155df7bb48a421431fc4c34d08e904
diff --git a/Lib/ntpath.py b/Lib/ntpath.py
@@ -118,6 +118,21 @@ def join(path, *paths):
        raise


+# Interesting findings about extended paths:
+# * '\\?\c:\a' is an extended path, which bypasses normal Windows API
+#   path processing. Thus relative paths are not resolved and slash is not
+#   translated to backslash. It has the native NT path limit of 32767
+#   characters, but a bit less after resolving device symbolic links,
+#   such as '\??\C:' => '\Device\HarddiskVolume2'.
+# * '\\?\c:/a' looks for a device named 'C:/a' because slash is a
+#   regular name character in the object namespace.
+# * '\\?\c:\foo/bar' is invalid because '/' is illegal in NT filesystems.
+#   The only path separator at the filesystem level is backslash.
+# * '//?/c:\a' and '//?/c:/a' are effectively equivalent to '\\.\c:\a' and
+#   thus limited to MAX_PATH.
+# * Prior to Windows 8, ANSI API bytes paths are limited to MAX_PATH,
+#   even with the '\\?\' prefix.
+
 # Split a path in a drive specification (a drive letter followed by a
 # colon) and the path specification.
 # It is always true that drivespec + pathspec == p