.o could be COFF object.

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 434 matching lines @@
   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')
+      if (sys.platform == 'win32'
+          and os.path.splitext(first_filepath)[1] in ('.obj', '.o')

[M-A Ruel, 2016/09/13 14:20:22]

I would prefer '.o', '.obj' so they are in order.

[Yoshisato Yanagisawa, 2016/09/14 01:04:36]

Done.

           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:
@@ skipping 209 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())