[NaCl SDK] Fixup GCC-generated .d files (second attempt)

The change adds a script that will post-procress
gcc-generated .d files such that they do not have
file-not-found issue when headers are removed or
renamed.

Also, fix an issue in common.mk where it was checking
for IGNORE_DEPS incorrectly.  This was causing dependencies
to always be built which was leading to duplicate builds
of the same project causing race conditions in the build
system.

R=binji@chromium.org
BUG=None

Review URL: https://codereview.chromium.org/17769006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@209229 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 95 insertions, 0 deletions

diff --git a/native_client_sdk/src/tools/fix_deps.py b/native_client_sdk/src/tools/fix_deps.py
new file mode 100755
index 0000000..a10feac
--- /dev/null
+++ b/native_client_sdk/src/tools/fix_deps.py
@@ -0,0 +1,95 @@
+#!/usr/bin/env python
+# Copyright (c) 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Fixup GCC-generated dependency files.
+
+Modify GCC generated dependency files in-place so they are more suitable
+for including in a GNU Makefile.  Without the fixups, deleting or renaming
+headers can cause the build to be broken. See:
+http://mad-scientist.net/make/autodep.html for more details of the problem.
+"""
+
+import os
+import optparse
+import sys
+
+TAG_LINE = '# Updated by fix_deps.py\n'
+
+
+class Error(Exception):
+  pass
+
+
+def ParseLine(line, new_target):
+  """Parse one line of a GCC-generated deps file.
+
+  Each line contains an optional target and then a list
+  of space seperated dependencies.  Spaces within filenames
+  are escaped with a backslash.
+  """
+  filenames = []
+
+  if new_target and ':' in line:
+    line = line.split(':', 1)[1]
+
+  line = line.strip()
+  line = line.rstrip('\\')
+
+  while True:
+    # Find the next non-escaped space
+    line = line.strip()
+    pos = line.find(' ')
+    while pos > 0 and line[pos-1] == '\\':
+      pos = line.find(' ', pos+1)
+
+    if pos == -1:
+      filenames.append(line)
+      break
+    filenames.append(line[:pos])
+    line = line[pos+1:]
+
+  return filenames
+
+
+def FixupDepFile(filename):
+  if not os.path.exists(filename):
+    raise Error('File not found: %s' % filename)
+
+  outlines = [TAG_LINE]
+  deps = []
+  new_target = True
+  with open(filename) as infile:
+    for line in infile:
+      if line == TAG_LINE:
+        raise Error('Already processed: %s' % filename)
+      outlines.append(line)
+      deps += ParseLine(line, new_target)
+      new_target = line.endswith('\\')
+
+  # For every depenency found output a dummy target with no rules
+  for dep in deps:
+    outlines.append('%s:\n' % dep)
+
+  with open(filename, 'w') as outfile:
+    for line in outlines:
+      outfile.write(line)
+
+
+def main(argv):
+  usage = "usage: %prog [options] <dep_file ...>"
+  parser = optparse.OptionParser(usage=usage, description=__doc__)
+  args = parser.parse_args(argv)[1]
+  if not args:
+    raise parser.error('expected one or more files as arguments')
+  for arg in args:
+    FixupDepFile(arg)
+
+
+if __name__ == '__main__':
+  try:
+    sys.exit(main(sys.argv[1:]))
+  except Error as e:
+    sys.stderr.write('%s: %s\n' % (os.path.basename(__file__), e))
+    sys.exit(1)