Add landmines support.

build/landmines.py

Index: build/landmines.py
diff --git a/build/landmines.py b/build/landmines.py
new file mode 100755
index 0000000000000000000000000000000000000000..2b3d7753c0db9fe26b1b9e659a0b8600bbadc287
--- /dev/null
+++ b/build/landmines.py
@@ -0,0 +1,129 @@
+#!/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.
+
+A landmine is tripped when a builder checks out a different revision, and the
+diff between the new landmines and the old ones is non-null. At this point, the
+build is clobbered.
+"""
+
+import difflib
+import logging
+import optparse
+import os
+import sys
+import subprocess
+import time
+
+import landmine_utils
+
+
+SRC_DIR = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))
+
+
+def get_target_build_dir(build_tool, target):
+  """
+  Returns output directory absolute path dependent on build and targets.
+  Examples:
+    r'c:\b\build\slave\win\build\src\out\Release'
+    '/mnt/data/b/build/slave/linux/build/src/out/Debug'
+    '/b/build/slave/ios_rel_device/build/src/xcodebuild/Release-iphoneos'
+
+  Keep this function in sync with tools/build/scripts/slave/compile.py
+  """
+  ret = None
+  if build_tool == 'xcode':
+    ret = os.path.join(SRC_DIR, 'xcodebuild', target)
+  elif build_tool in ['make', 'ninja', 'ninja-ios']:  # TODO: Remove ninja-ios.
+    ret = os.path.join(SRC_DIR, 'out', target)
+  elif build_tool in ['msvs', 'vs', 'ib']:
+    ret = os.path.join(SRC_DIR, 'build', target)
+  else:
+    raise NotImplementedError('Unexpected GYP_GENERATORS (%s)' % build_tool)
+  return os.path.abspath(ret)
+
+
+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)
+
+      with open(triggered, 'w') as f:
+        f.writelines(diff)
+    elif os.path.exists(triggered):
+      # Remove false triggered landmines.
+      os.remove(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')],
+      help='Path to the script which emits landmines to stdout. The target '
+           'is passed to this script via option -t. Note that an extra '
+           'script can be specified via an env var EXTRA_LANDMINES_SCRIPT.')
+  parser.add_option('-v', '--verbose', action='store_true',
+      default=('LANDMINES_VERBOSE' in os.environ),
+      help=('Emit some extra debugging information (default off). This option '
+          'is also enabled by the presence of a LANDMINES_VERBOSE environment '
+          'variable.'))
+
+  options, args = parser.parse_args()
+
+  if args:
+    parser.error('Unknown arguments %s' % args)
+
+  logging.basicConfig(
+      level=logging.DEBUG if options.verbose else logging.ERROR)
+
+  extra_script = os.environ.get('EXTRA_LANDMINES_SCRIPT')
+  if extra_script:
+    return options.landmine_scripts + [extra_script]
+  else:
+    return options.landmine_scripts
+
+
+def main():
+  landmine_scripts = process_options()
+
+  if landmine_utils.builder() in ('dump_dependency_json', 'eclipse'):
+    return 0
+
+  landmines = []
+  for s in landmine_scripts:
+    proc = subprocess.Popen([sys.executable, s], stdout=subprocess.PIPE)
+    output, _ = proc.communicate()
+    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())