Skip COFF timestamp difference.

tools/determinism/compare_build_artifacts.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 """Compare the artifacts from two builds."""
 
 import difflib
 import json
 import optparse
@@ skipping 427 matching lines @@
 
 def diff_binary(first_filepath, second_filepath, file_len):
   """Returns a compact binary diff if the diff is small enough."""
   CHUNK_SIZE = 32
   MAX_STREAMS = 10
   diffs = 0
   streams = []
   offset = 0
   with open(first_filepath, 'rb') as lhs:
     with open(second_filepath, 'rb') as rhs:
+      # Skip part of Win32 COFF header if timestamps are different.
+      #
+      # COFF header:
+      #   0 -  1: magic.
+      #   2 -  3: # sections.
+      #   4 -  7: timestamp.
+      #   ....
+      COFF_HEADER_TO_COMPARE_SIZE = 8
+      if (sys.platform == 'win32' and first_filepath.endswith('.obj')
+          and file_len > COFF_HEADER_TO_COMPARE_SIZE):
+        rhs_data = rhs.read(COFF_HEADER_TO_COMPARE_SIZE)
+        lhs_data = lhs.read(COFF_HEADER_TO_COMPARE_SIZE)
+        if lhs_data[0:4] == rhs_data[0:4] and lhs_data[4:8] != rhs_data[4:8]:
+          offset += COFF_HEADER_TO_COMPARE_SIZE
+        else:
+          lhs.seek(0)
+          rhs.seek(0)
+
       while True:
         lhs_data = lhs.read(CHUNK_SIZE)
         rhs_data = rhs.read(CHUNK_SIZE)
         if not lhs_data:
           break
         if lhs_data != rhs_data:
           diffs += sum(l != r for l, r in zip(lhs_data, rhs_data))
           if streams is not None:
             if len(streams) < MAX_STREAMS:
               streams.append((offset, lhs_data, rhs_data))
@@ skipping 94 matching lines @@
       # for this case.
       print 'deps on %s are different: %s' % (
           target, set(first_deps).symmetric_difference(set(second_deps)))
       continue
     max_filepath_len = max(len(n) for n in first_deps)
     for d in first_deps:
       first_file = os.path.join(first_dir, d)
       second_file = os.path.join(second_dir, d)
       result = compare_files(first_file, second_file)
       if result:
-        print('%-*s: %s' % (max_filepath_len, d, result))
+        print('  %-*s: %s' % (max_filepath_len, d, result))
 
 
 def compare_build_artifacts(first_dir, second_dir, target_platform,
                             recursive=False):
   """Compares the artifacts from two distinct builds."""
   if not os.path.isdir(first_dir):
     print >> sys.stderr, '%s isn\'t a valid directory.' % first_dir
     return 1
   if not os.path.isdir(second_dir):
     print >> sys.stderr, '%s isn\'t a valid directory.' % second_dir
@@ skipping 85 matching lines @@
     parser.error('--target-platform is required')
 
   return compare_build_artifacts(os.path.abspath(options.first_build_dir),
                                  os.path.abspath(options.second_build_dir),
                                  options.target_platform,
                                  options.recursive)
 
 
 if __name__ == '__main__':
   sys.exit(main())