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 . -- [:MattDoar]  . -- [[MattDoar]]

The function presented here is useful if:

  • You've got one environment used to create many targets (too many to start messing with).
  • The environment is configured differently for different platforms/compilers/etc.
  • Some platforms/compilers/etc. need an additional source file to be compiled in order to work properly. This can be, for example, a replacement for a library that is not available on a certain platform.

This function wraps a given emitter with another emitter that adds another file to the source nodes.

Replaceable emitters (as of SCons 0.96.90):

  • PROGEMITTER - emitter for Program builder

  • SHLIBEMITTER - emitter for SharedLibrary builder

  • LIBEMITTER - emitter for Library builder

The Function

   1 def add_file_to_emitter(env, emitter_name, file):
   2   try:
   3     original_emitter = env[emitter_name]
   4     if type(original_emitter) == list:
   5       original_emitter = original_emitter[0]
   6   except KeyError:
   7     original_emitter = None
   8   def emitter(target, source, env):
   9     if original_emitter:
  10       target, source = original_emitter(target, source, env)
  11     return target, source + [file]
  12   env[emitter_name] = emitter

Example Usage

In this example, the environment is searched for a library called somelib. If this library is not found, add_file_to_emitter is called to add somelibreplacement.c to every program built using the environment.

   1 env = Environment()
   2 conf = env.Configure()
   3 if not conf.CheckLib('somelib'):
   4   add_file_to_emitter(env, 'PROGEMITTER', File('somelibreplacement.c'))
   5 conf.Finish()

Changing the Emitter for StaticObject

If you want to change where a builder finds its C/C++ source files, you want to change the emitter for the StaticObject builder, aka Object. Unfortunately, there is no OBJEMITTER currently defined, but another way to do it is shown below.

   1 # Assuming the BUILD_DIR is set to the location of the generated files
   2 # and some other generated files are in OTHER_BUILD_DIR
   3 def my_emitter(target, source, env):
   4     ''' Tell SCons about the locations of some generated files. This could
   5         be any emitter you want'''
   6     if os.path.exists(source[0].path):
   7         # The source file was generated in the local build directory
   8         return (target, source)
   9     altSrcName = source[0].abspath.replace(env['BUILD_DIR'] + os.sep, '')
  10     if os.path.exists(altSrcName):
  11         # The source file is in the source directory
  12         return (target, altSrcName)
  13     # Assume that the source file is in the other generated files build directory
  14     altSrcName = "%s/%s%s" % (File('#'), env['OTHER_BUILD_DIR'],
  15                   source[0].path.replace(env['OTHER_BUILD_DIR'], ''))
  16     return (target, altSrcName)
  17 # This is the part where we override the emitter for the Object builder
  18 from SCons.Tool import createObjBuilders
  19 # Get the underlying builder objects
  20 static_obj, shared_obj = createObjBuilders(env)
  21 # Now SCons can find .cpp files in different locations
  22 static_obj.add_emitter('.cpp', my_emitter)

AddFilesDynamically (last edited 2008-03-12 02:47:13 by localhost)