Enabling splitting building with snapshots in to building the mksnapshot...

Enabling splitting building with snapshots in to building the mksnapshot executable and building with a snapshot to facilitate building for ARM with a crosstool compiler.
Review URL: http://codereview.chromium.org/19014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1188 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

SConstruct

@@ -303,7 +303,7 @@ SIMPLE_OPTIONS = {
     'help': 'the architecture to build for'
   },
   'snapshot': {
-    'values': ['on', 'off'],
+    'values': ['on', 'off', 'nobuild'],
     'default': 'off',
     'help': 'build using snapshots for faster start-up'
   },
@@ -396,13 +396,15 @@ class BuildContext(object):
 
   def __init__(self, options, env_overrides, samples):
     self.library_targets = []
+    self.mksnapshot_targets = []
     self.cctest_targets = []
     self.sample_targets = []
     self.d8_targets = []
     self.options = options
     self.env_overrides = env_overrides
     self.samples = samples
-    self.use_snapshot = (options['snapshot'] == 'on')
+    self.use_snapshot = (options['snapshot'] != 'off')
+    self.build_snapshot = (options['snapshot'] == 'on')
     self.flags = None
 
   def AddRelevantFlags(self, initial, flags):
@@ -496,6 +498,7 @@ def BuildSpecific(env, mode, env_overrides):
 
   context.flags = {
     'v8': v8_flags,
+    'mksnapshot': v8_flags,
     'jscre': jscre_flags,
     'dtoa': dtoa_flags,
     'cctest': cctest_flags,
@@ -509,13 +512,15 @@ def BuildSpecific(env, mode, env_overrides):
   env['LIBRARY'] = library_name
 
   # Build the object files by invoking SCons recursively.  
-  (object_files, shell_files) = env.SConscript(
+  (object_files, shell_files, mksnapshot) = env.SConscript(
     join('src', 'SConscript'),
     build_dir=join('obj', target_id),
     exports='context',
     duplicate=False
   )
 
+  context.mksnapshot_targets.append(mksnapshot)
+
   # Link the object files into a library.
   env.Replace(**context.flags['v8'])
   context.ApplyEnvOverrides(env)
@@ -570,6 +575,7 @@ def Build():
   SourceSignatures(env['sourcesignatures'])
 
   libraries = []
+  mksnapshots = []
   cctests = []
   samples = []
   d8s = []
@@ -577,11 +583,13 @@ def Build():
   for mode in modes:
     context = BuildSpecific(env.Copy(), mode, env_overrides)
     libraries += context.library_targets
+    mksnapshots += context.mksnapshot_targets
     cctests += context.cctest_targets
     samples += context.sample_targets
     d8s += context.d8_targets
 
   env.Alias('library', libraries)
+  env.Alias('mksnapshot', mksnapshots)
   env.Alias('cctests', cctests)
   env.Alias('sample', samples)
   env.Alias('d8', d8s)

src/SConscript

@@ -150,18 +150,20 @@ def ConfigureObjectFiles():
 
   # Create snapshot if necessary.
   empty_snapshot_obj = context.ConfigureObject(env, 'snapshot-empty.cc')
+  mksnapshot_src = 'mksnapshot.cc'
+  mksnapshot = env.Program('mksnapshot', [mksnapshot_src, libraries_obj, non_snapshot_files, empty_snapshot_obj], PDB='mksnapshot.exe.pdb')
   if context.use_snapshot:
-    mksnapshot_src = 'mksnapshot.cc'
-    mksnapshot = env.Program('mksnapshot', [mksnapshot_src, libraries_obj, non_snapshot_files, empty_snapshot_obj], PDB='mksnapshot.exe.pdb')
-    snapshot_cc = env.Snapshot('snapshot.cc', mksnapshot, LOGFILE=File('snapshot.log').abspath)
+    if context.build_snapshot:
+      snapshot_cc = env.Snapshot('snapshot.cc', mksnapshot, LOGFILE=File('snapshot.log').abspath)
+    else:
+      snapshot_cc = Command('snapshot.cc', [], [])
     snapshot_obj = context.ConfigureObject(env, snapshot_cc, CPPPATH=['.'])
     libraries_obj = context.ConfigureObject(env, libraries_empty_src, CPPPATH=['.'])
   else:
     snapshot_obj = empty_snapshot_obj
-
   library_objs = [non_snapshot_files, libraries_obj, snapshot_obj]
-  return (library_objs, d8_objs)
+  return (library_objs, d8_objs, [mksnapshot])
 
 
-(library_objs, d8_objs) = ConfigureObjectFiles()
-Return('library_objs d8_objs')
+(library_objs, d8_objs, mksnapshot) = ConfigureObjectFiles()
+Return('library_objs d8_objs mksnapshot')