Use flock-style lock on Windows to limit number of concurrent links

pylib/gyp/win_tool.py

 #!/usr/bin/env python
 
 # 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.
 
 """Utility functions for Windows builds.
 
 These functions are executed via gyp-win-tool when using the ninja generator.
 """
 
 import os
 import shutil
 import subprocess
 import sys
+import win32con
+import win32file
+import pywintypes
 
 
 def main(args):
   executor = WinTool()
   exit_code = executor.Dispatch(args)
   if exit_code is not None:
     sys.exit(exit_code)
 
 
+class LinkLock(object):
+  """A flock-style lock to limit the number of concurrent links to one. Based on
+  http://code.activestate.com/recipes/65203-portalocker-cross-platform-posixnt-api-for-flock-s/
+  """
+  def __enter__(self):
+    self.file = open('LinkLock', 'w+')
+    self.file_handle = win32file._get_osfhandle(self.file.fileno())
+    win32file.LockFileEx(self.file_handle, win32con.LOCKFILE_EXCLUSIVE_LOCK,
+                         0, -0x10000, pywintypes.OVERLAPPED())
+
+  def __exit__(self, type, value, traceback):
+    win32file.UnlockFileEx(
+        self.file_handle, 0, -0x10000, pywintypes.OVERLAPPED())
+    self.file.close()
+
+
 class WinTool(object):
   """This class performs all the Windows tooling steps. The methods can either
   be executed directly, or dispatched from an argument list."""
 
   def Dispatch(self, args):
     """Dispatches a string command to a method."""
     if len(args) < 1:
       raise Exception("Not enough arguments")
 
     method = "Exec%s" % self._CommandifyName(args[0])
@@ skipping 26 matching lines @@
     if os.path.isdir(source):
       shutil.copytree(source, dest)
     else:
       shutil.copy2(source, dest)
 
   def ExecLinkWrapper(self, arch, *args):
     """Filter diagnostic output from link that looks like:
     '   Creating library ui.dll.lib and object ui.dll.exp'
     This happens when there are exports from the dll or exe.
     """
-    env = self._GetEnv(arch)
-    popen = subprocess.Popen(args, shell=True, env=env,
-                             stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
-    out, _ = popen.communicate()
-    for line in out.splitlines():
-      if not line.startswith('   Creating library '):
-        print line
-    return popen.returncode
+    with LinkLock():
+      env = self._GetEnv(arch)
+      popen = subprocess.Popen(args, shell=True, env=env,
+                               stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+      out, _ = popen.communicate()
+      for line in out.splitlines():
+        if not line.startswith('   Creating library '):
+          print line
+      return popen.returncode
 
   def ExecManifestWrapper(self, arch, *args):
     """Run manifest tool with environment set. Strip out undesirable warning
     (some XML blocks are recognized by the OS loader, but not the manifest
     tool)."""
     env = self._GetEnv(arch)
     popen = subprocess.Popen(args, shell=True, env=env,
                              stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
     out, _ = popen.communicate()
     for line in out.splitlines():
@@ skipping 76 matching lines @@
     for |arch|. If |dir| is supplied, use that as the working directory."""
     env = self._GetEnv(arch)
     args = open(rspfile).read()
     dir = dir[0] if dir else None
     popen = subprocess.Popen(args, shell=True, env=env, cwd=dir)
     popen.wait()
     return popen.returncode
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))