[libfuzzer] support of custom libfuzzer options via .options file.

testing/libfuzzer/gen_fuzzer_runner.py

 #!/usr/bin/python
 #
 # Copyright (c) 2015 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.
 
 """Generate .sh runner for libfuzzer test.
 
 Invoked by GN from fuzzer_test.gni.
 """
 
 import argparse
 import os
 import sys
 
 
-parser = argparse.ArgumentParser(description="Generate fuzzer launcher.")
-parser.add_argument('--fuzzer', required=True)
-parser.add_argument('--launcher', required=True)
-parser.add_argument('--dict', required=True)
-args = parser.parse_args()
-
-out = open(args.launcher, 'w')
-out.write("""#!/bin/bash
+LAUNCHER_TEMPLATE = """#!/bin/bash
 set -ue
 DIR=$(dirname $0)
-$DIR/%(fuzzer)s -dict=$DIR/%(dict)s $*
-""" % { "fuzzer": args.fuzzer, "dict": args.dict })
-out.close()
+$DIR/%(fuzzer)s %(arguments)s
+"""
 
-os.chmod(args.launcher, os.stat(args.launcher).st_mode | 0o111) # chmod a+x
+
+def buildFuzzerArguments(args):

[Oliver Chang, 2016/02/18 22:31:42]

nit: follow chromium python style guide
(https://www.chromium.org/chromium-os/python-style-guidelines) and NameLikeThis
(first letter capitalised).

+  fuzzer_arguments = ""
+  if args.dict:
+    fuzzer_arguments += "-dict=$DIR/%(dict)s " % { "dict": args.dict }
+
+  fuzzer_arguments += "$*"
+
+  # Put custom parameters after $* to overwrite default values from ClusterFuzz.

[Oliver Chang, 2016/02/18 22:31:42]

Why do we want to override values from ClusterFuzz?

If specifying the same argument again overwrites the previous value, I think it
would be useful for someone (not just ClusterFuzz) to be able to override a
specific default when running this wrapper.

+  if args.params:
+    fuzzer_arguments += " %(params)s" % { "params": args.params[1 : -1]}

[Oliver Chang, 2016/02/18 22:31:42]

why is the quoting in fuzzer_test.gni necessary if you are removing it here in
args.params[1 : -1] ? Does GN quote the strings for you?

+
+  return fuzzer_arguments
+
+
+def main():
+  parser = argparse.ArgumentParser(description="Generate fuzzer launcher.")
+  parser.add_argument('--fuzzer', required=True)
+  parser.add_argument('--launcher', required=True)
+  parser.add_argument('--dict', required=False)
+  parser.add_argument('--params', required=False)
+  args = parser.parse_args()
+
+  fuzzer_arguments = buildFuzzerArguments(args)
+
+  launcher_source_code = LAUNCHER_TEMPLATE % {"fuzzer": args.fuzzer,
+                                              "arguments": fuzzer_arguments}
+
+  out = open(args.launcher, 'w')
+  out.write(launcher_source_code)
+  out.close()
+
+  os.chmod(args.launcher, os.stat(args.launcher).st_mode | 0o111) # chmod a+x
+
+
+if __name__ == '__main__':
+  main()