On Windows, don't try to create relative paths across different drives

pylib/gyp/common.py

 # Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from __future__ import with_statement
 
 import errno
 import filecmp
 import os.path
 import re
@@ skipping 113 matching lines @@
 @memoize
 def RelativePath(path, relative_to):
   # Assuming both |path| and |relative_to| are relative to the current
   # directory, returns a relative path that identifies path relative to
   # relative_to.
 
   # Convert to normalized (and therefore absolute paths).
   path = os.path.realpath(path)
   relative_to = os.path.realpath(relative_to)
 
+  # On Windows, we can't create a relative path to a different drive, so just
+  # use the absolute path.
+  if os.name == 'nt':

[scottmg, 2013/07/19 16:51:17]

i'm not sure whether this will work on cygwin... isn't there some /cygdrive/
crud it uses instead? does splitdrive work on that? so maybe sys.platform ==
'win32' makes more sense. (other places use sys.platform, so if you think it
works on cygwin, then sys.platform in ('win32', 'cygwin') for consistency)

[borenet, 2013/07/19 17:58:42]

Changed to use sys.platform == "win32".  I just verified that this isn't
necessary on cygwin, since relative paths do work between drives, because of the
/cygdrive prefix and Unix-style paths.

+    if (os.path.splitdrive(path)[0].lower() !=
+        os.path.splitdrive(relative_to)[0].lower()):
+      return path
+
   # Split the paths into components.
   path_split = path.split(os.path.sep)
   relative_to_split = relative_to.split(os.path.sep)
 
   # Determine how much of the prefix the two paths share.
   prefix_len = len(os.path.commonprefix([path_split, relative_to_split]))
 
   # Put enough ".." components to back up out of relative_to to the common
   # prefix, and then append the part of path_split after the common prefix.
   relative_split = [os.path.pardir] * (len(relative_to_split) - prefix_len) + \
@@ skipping 338 matching lines @@
       return
     visited.add(node)
     visiting.add(node)
     for neighbor in get_edges(node):
       Visit(neighbor)
     visiting.remove(node)
     ordered_nodes.insert(0, node)
   for node in sorted(graph):
     Visit(node)
   return ordered_nodes