Introduce safe_ensure_dirs as a safe os.makedirs replacement.

It only uses os.makedirs call, which is more atomic than calling 2 procs. Thus exception due to already existent directory should not longer occur.

tools/cache.py

@@ -1,6 +1,7 @@
 import os.path, sys, shutil, hashlib, cPickle, zlib, time
 
 import tempfiles
+import shared
 
 # Permanent cache for dlmalloc and stdlibc++
 class Cache:
@@ -13,13 +14,7 @@ def __init__(self, dirname=None, debug=False):
     self.debug = debug
 
   def ensure(self):
-    try:
-      # Use makedirs here, so creating the path is as atomic as possible
-      os.makedirs(self.dirname)
-    except os.error, e:
-      # Ignore error for already existing dirname
-      if not os.path.exists(self.dirname):
-        raise e
+    shared.safe_ensure_dirs(self.dirname)
 
   def erase(self):
     tempfiles.try_delete(self.dirname)
@@ -53,11 +48,7 @@ def __init__(self, cache):
 
   def ensure(self):
     self.cache.ensure()
-    if not os.path.exists(self.dirname):
-      try:
-        os.makedirs(self.dirname)
-      except (IOError, OSError):
-        pass
+    shared.safe_ensure_dirs(self.dirname)
 
   def get_shortkey(self, keys):
     if type(keys) not in [list, tuple]:

tools/shared.py

@@ -1,4 +1,4 @@
-import shutil, time, os, sys, json, tempfile, copy, shlex, atexit, subprocess, hashlib, cPickle, re
+import shutil, time, os, sys, json, tempfile, copy, shlex, atexit, subprocess, hashlib, cPickle, re, errno
 from subprocess import Popen, PIPE, STDOUT
 from tempfile import mkstemp
 from distutils.spawn import find_executable
@@ -480,8 +480,7 @@ def __init__(self, environ=os.environ):
     if self.DEBUG:
       try:
         self.EMSCRIPTEN_TEMP_DIR = self.CANONICAL_TEMP_DIR
-        if not os.path.exists(self.EMSCRIPTEN_TEMP_DIR):
-          os.makedirs(self.EMSCRIPTEN_TEMP_DIR)
+        safe_ensure_dirs(self.EMSCRIPTEN_TEMP_DIR)
       except Exception, e:
         logging.debug(e + 'Could not create canonical temp dir. Check definition of TEMP_DIR in ~/.emscripten')
 
@@ -1017,8 +1016,7 @@ def link(files, target, force_archive_contents=False):
         try:
           temp_dir = os.path.join(EMSCRIPTEN_TEMP_DIR, 'ar_output_' + str(os.getpid()) + '_' + str(len(temp_dirs)))
           temp_dirs.append(temp_dir)
-          if not os.path.exists(temp_dir):
-            os.makedirs(temp_dir)
+          safe_ensure_dirs(temp_dir)
           os.chdir(temp_dir)
           contents = filter(lambda x: len(x) > 0, Popen([LLVM_AR, 't', f], stdout=PIPE).communicate()[0].split('\n'))
           #print >> sys.stderr, '  considering archive', f, ':', contents
@@ -1027,8 +1025,8 @@ def link(files, target, force_archive_contents=False):
           else:
             for content in contents: # ar will silently fail if the directory for the file does not exist, so make all the necessary directories
               dirname = os.path.dirname(content)
-              if dirname and not os.path.exists(dirname):
-                os.makedirs(dirname)
+              if dirname:
+                safe_ensure_dirs(dirname)
             Popen([LLVM_AR, 'xo', f], stdout=PIPE).communicate() # if absolute paths, files will appear there. otherwise, in this directory
             contents = map(lambda content: os.path.join(temp_dir, content), contents)
             contents = filter(os.path.exists, map(os.path.abspath, contents))
@@ -1637,5 +1635,17 @@ def unsuffixed(name):
 def unsuffixed_basename(name):
   return os.path.basename(unsuffixed(name))
 
+def safe_ensure_dirs(dirname):
+  try:
+    os.makedirs(dirname)
+  except os.error, e:
+    # Ignore error for already existing dirname
+    if e.errno != errno.EEXIST:
+      raise e
+    # FIXME: Notice that this will result in a false positive,
+    # should the dirname be a file! There seems to no way to
+    # handle this atomically in Python 2.x.
+    # There is an additional option for Python 3.x, though.
+
 import js_optimizer