Enable GN ASAN builds for Linux

tools/gn.py

 #!/usr/bin/env python
 # Copyright 2016 The Dart 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.
 
 import argparse
 import multiprocessing
 import os
 import subprocess
 import sys
@@ skipping 69 matching lines @@
     pub = pub + ".bat"
   gn_args['dart_host_pub_exe'] = os.path.join(
       DART_ROOT, 'tools', 'sdks', host_os, 'dart-sdk', 'bin', pub)
 
   # For Fuchsia support, the default is to not compile in the root
   # certificates.
   gn_args['dart_use_fallback_root_certificates'] = True
 
   gn_args['dart_zlib_path'] = "//runtime/bin/zlib"
 
-  gn_args['dart_use_tcmalloc'] = gn_args['target_os'] == 'linux'
+  # Use tcmalloc only when targeting Linux and when not using ASAN.
+  gn_args['dart_use_tcmalloc'] = (gn_args['target_os'] == 'linux'
+                                  and not args.asan)
 
   gn_args['is_debug'] = mode == 'debug'
   gn_args['is_release'] = mode == 'release'
   gn_args['is_product'] = mode == 'product'
   gn_args['dart_debug'] = mode == 'debug'
 
   # This setting is only meaningful for Flutter. Standalone builds of the VM
   # should leave this set to 'develop', which causes the build to defer to
   # 'is_debug', 'is_release' and 'is_product'.
   gn_args['dart_runtime_mode'] = 'develop'
 
   # TODO(zra): Investigate using clang with these configurations.
   has_clang = (host_os != 'win'
                and args.os not in ['android']
                and not gn_args['target_cpu'].startswith('arm')
                and not gn_args['target_cpu'].startswith('mips'))
   gn_args['is_clang'] = args.clang and has_clang
 
+  gn_args['is_asan'] = args.asan and gn_args['is_clang']
+
   if args.target_sysroot:
     gn_args['target_sysroot'] = args.target_sysroot
 
   if args.toolchain_prefix:
     gn_args['toolchain_prefix'] = args.toolchain_prefix
 
   goma_dir = os.environ.get('GOMA_DIR')
   goma_home_dir = os.path.join(os.getenv('HOME', ''), 'goma')
   if args.goma and goma_dir:
     gn_args['use_goma'] = True
@@ skipping 72 matching lines @@
       type=str,
       help='Target OSs (comma-separated).',
       metavar='[all,host,android]',
       default='host')
   parser.add_argument('--arch', '-a',
       type=str,
       help='Target architectures (comma-separated).',
       metavar='[all,ia32,x64,simarm,arm,simarmv6,armv6,simarmv5te,armv5te,'
               'simmips,mips,simarm64,arm64,simdbc,armsimdbc]',
       default='x64')
+  parser.add_argument('--asan',
+      help='Build with ASAN',
+      default=False,
+      action='store_true')
   parser.add_argument('--goma',
       help='Use goma',
       default=True,
       action='store_true')
   parser.add_argument('--no-goma',
       help='Disable goma',
       dest='goma',
       action='store_false')
   parser.add_argument('--clang',
       help='Use Clang',
@@ skipping 71 matching lines @@
       return 1
 
   endtime = time.time()
   if args.verbose:
     print ("GN Time: %.3f seconds" % (endtime - starttime))
   return 0
 
 
 if __name__ == '__main__':
     sys.exit(main(sys.argv))