gn: make some warning flags match gyp more closely

tools/gn/bin/gyp_flag_compare.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.
 
 """Given the output of -t commands from a ninja build for a gyp and GN generated
 build, report on differences between the command lines."""
 
 
@@ skipping 68 matching lines @@
       'depname': dep_name,
       'defines': sorted(defines),
       'include_dirs': sorted(include_dirs),  # TODO(scottmg): This is wrong.
       'dash_f': sorted(dash_f),
       'warnings': sorted(warnings),
       'other': sorted(others),
     }
   return flags_by_output
 
 
-def CompareLists(gyp, gn, name, dont_care=None):
-  """Return a report of any differences between two lists, ignoring anything
-  in |dont_care|."""
-  if not dont_care:
-    dont_care = []
+def CompareLists(gyp, gn, name, dont_care_gyp=None, dont_care_gn=None):
+  """Return a report of any differences between gyp and gn lists, ignoring
+  anything in |dont_care_{gyp|gn}| respectively."""
+  if not dont_care_gyp:
+    dont_care_gyp = []
+  if not dont_care_gn:
+    dont_care_gn = []
   output = ''
   if gyp[name] != gn[name]:
     output += '  %s differ:\n' % name
-    gyp_set = set(gyp[name]) - set(dont_care)
-    gn_set = set(gn[name]) - set(dont_care)
-    output += '    In gyp, but not in GN:\n      %s' % '\n      '.join(
-        sorted(gyp_set - gn_set)) + '\n'
-    output += '    In GN, but not in gyp:\n      %s' % '\n      '.join(
-        sorted(gn_set - gyp_set)) + '\n\n'
+    gyp_set = set(gyp[name])
+    gn_set = set(gn[name])
+    missing_in_gyp = gyp_set - gn_set
+    missing_in_gn = gn_set - gyp_set
+    missing_in_gyp -= set(dont_care_gyp)
+    missing_in_gn -= set(dont_care_gn)
+    if missing_in_gyp:
+      output += '    In gyp, but not in GN:\n      %s' % '\n      '.join(
+          sorted(missing_in_gyp)) + '\n'
+    if missing_in_gn:
+      output += '    In GN, but not in gyp:\n      %s' % '\n      '.join(
+          sorted(missing_in_gn)) + '\n\n'
   return output
 
 
 def Run(command_line):
   """Run |command_line| as a subprocess and return stdout. Raises on error."""
   return subprocess.check_output(command_line, shell=True)
 
 
 def main():
   if len(sys.argv) != 2 and len(sys.argv) != 3:
     print 'usage: %s gyp_target gn_target' % __file__
     print '   or: %s target' % __file__
     return 1
 
   if len(sys.argv) == 2:
     sys.argv.append(sys.argv[1])
 
   print >>sys.stderr, 'Regenerating...'
   # Currently only Release, non-component.
   Run('gn gen out/gn_flags --args="is_debug=false is_component_build=false"')
-  del os.environ['GYP_DEFINES']
+  os.environ.pop('GYP_DEFINES', None)
   Run('python build/gyp_chromium -Goutput_dir=out_gyp_flags -Gconfig=Release')
   gn = Run('ninja -C out/gn_flags -t commands %s' % sys.argv[2])
   gyp = Run('ninja -C out_gyp_flags/Release -t commands %s' % sys.argv[1])
   all_gyp_flags = GetFlags(gyp.splitlines())
   all_gn_flags = GetFlags(gn.splitlines())
   gyp_files = set(all_gyp_flags.keys())
   gn_files = set(all_gn_flags.keys())
   different_source_list = gyp_files != gn_files
   if different_source_list:
     print 'Different set of sources files:'
     print '  In gyp, not in GN:\n    %s' % '\n    '.join(
         sorted(gyp_files - gn_files))
     print '  In GN, not in gyp:\n    %s' % '\n    '.join(
         sorted(gn_files - gyp_files))
     print '\nNote that flags will only be compared for files in both sets.\n'
   file_list = gyp_files & gn_files
   files_with_given_differences = {}
   for filename in sorted(file_list):
     gyp_flags = all_gyp_flags[filename]
     gn_flags = all_gn_flags[filename]
     differences = CompareLists(gyp_flags, gn_flags, 'dash_f')
-    differences += CompareLists(gyp_flags, gn_flags, 'defines', dont_care=[
-        '-DENABLE_PRE_SYNC_BACKUP',
-        '-DENABLE_WEBRTC=1',
-        '-DUSE_LIBJPEG_TURBO=1',
-        '-DUSE_PANGO=1',
-        '-DUSE_SYMBOLIZE',
+    differences += CompareLists(gyp_flags, gn_flags, 'defines')
+    differences += CompareLists(gyp_flags, gn_flags, 'include_dirs')
+    differences += CompareLists(gyp_flags, gn_flags, 'warnings', dont_care_gn=[
+        # More conservative warnings in GN we consider to be OK.
+        '-Wendif-labels',
+        '-Wextra',
+        '-Wsign-compare',
         ])
-    differences += CompareLists(gyp_flags, gn_flags, 'include_dirs')
-    differences += CompareLists(gyp_flags, gn_flags, 'warnings')
     differences += CompareLists(gyp_flags, gn_flags, 'other')
     if differences:
       files_with_given_differences.setdefault(differences, []).append(filename)
 
   for diff, files in files_with_given_differences.iteritems():
     print '\n'.join(sorted(files))
     print diff
 
   return 1 if files_with_given_differences or different_source_list else 0
 
 
 if __name__ == '__main__':
   sys.exit(main())