Make landmines work on the first landmine.

build/landmines.py

 #!/usr/bin/env python
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 This script runs every build as a hook. If it detects that the build should
 be clobbered, it will touch the file <build_dir>/.landmine_triggered. The
 various build scripts will then check for the presence of this file and clobber
 accordingly. The script will also emit the reasons for the clobber to stdout.
@@ skipping 40 matching lines @@
 
 
 def set_up_landmines(target, new_landmines):
   """Does the work of setting, planting, and triggering landmines."""
   out_dir = get_target_build_dir(landmine_utils.builder(), target)
 
   landmines_path = os.path.join(out_dir, '.landmines')
   if not os.path.exists(out_dir):
     return
 
-  if os.path.exists(landmines_path):
-    triggered = os.path.join(out_dir, '.landmines_triggered')
-    with open(landmines_path, 'r') as f:
-      old_landmines = f.readlines()
-    if old_landmines != new_landmines:
-      old_date = time.ctime(os.stat(landmines_path).st_ctime)
-      diff = difflib.unified_diff(old_landmines, new_landmines,
-          fromfile='old_landmines', tofile='new_landmines',
-          fromfiledate=old_date, tofiledate=time.ctime(), n=0)
+  # Make sure the landmines tracker exists.
+  open(landmines_path, 'a').close()
 
-      with open(triggered, 'w') as f:
-        f.writelines(diff)
-    elif os.path.exists(triggered):
-      # Remove false triggered landmines.
-      os.remove(triggered)
+  triggered = os.path.join(out_dir, '.landmines_triggered')
+  with open(landmines_path, 'r') as f:
+    old_landmines = f.readlines()
+  if old_landmines != new_landmines:
+    old_date = time.ctime(os.stat(landmines_path).st_ctime)
+    diff = difflib.unified_diff(old_landmines, new_landmines,
+        fromfile='old_landmines', tofile='new_landmines',
+        fromfiledate=old_date, tofiledate=time.ctime(), n=0)
+
+    with open(triggered, 'w') as f:
+      f.writelines(diff)
+    print "Setting landmine: %s" % triggered

[Jakob Kummerow, 2014/07/23 11:05:48]

are you keeping these print statements intentionally?

+    print "Reason:\n%s" % diff
+  elif os.path.exists(triggered):
+    # Remove false triggered landmines.
+    os.remove(triggered)
+    print "Removing landmine: %s" % triggered
   with open(landmines_path, 'w') as f:
     f.writelines(new_landmines)
 
 
 def process_options():
   """Returns a list of landmine emitting scripts."""
   parser = optparse.OptionParser()
   parser.add_option(
       '-s', '--landmine-scripts', action='append',
       default=[os.path.join(SRC_DIR, 'build', 'get_landmines.py')],
@@ skipping 34 matching lines @@
     landmines.extend([('%s\n' % l.strip()) for l in output.splitlines()])
 
   for target in ('Debug', 'Release'):
     set_up_landmines(target, landmines)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())