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()
-- AmirSzekely
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)
-- MattDoar