SCons: How to use the same builders for multiple variants (release/debug) of a program

Question

The SCons User Guide tells about the usage of Multiple Construction Environments to build build multiple versions of a single program and gives the following example:

opt = Environment(CCFLAGS = '-O2')
dbg = Environment(CCFLAGS = '-g')

o = opt.Object('foo-opt', 'foo.c')
opt.Program(o)

d = dbg.Object('foo-dbg', 'foo.c')
dbg.Program(d)

Instead of manually assigning different names to the objects compiled with different environments, VariantDir() / variant_dir sounds like a better solution...

But if I place the Program() builder inside the SConscript:

Import('env')
env.Program('foo.c')

How can I export different environments to the same SConscript file?

opt = Environment(CCFLAGS = '-O2')
dbg = Environment(CCFLAGS = '-g')

SConscript('SConscript', 'opt', variant_dir='release') #'opt' --> 'env'???
SConscript('SConscript', 'dbg', variant_dir='debug')   #'dbg' --> 'env'???

Unfortunately the discussion in the SCons Wiki does not bring more insight to this topic.

Thanks for your input!

Answer 1

SConscript is a method defined on the environment itself:

for dir, env in (('release', opt), ('debug', dbg)):
    env.SConscript('SConscript', 'env', variant_dir=dir)

And then from the SConscript you can:

Import('env')

Answer 2

Alternately, you can pass a dictionary as the exports arg to SConscript. The keys are the name the SConscript will use to import it, and the values are the objects in the SConstruct. So:

SConscript('SConscript', exports={'env': dbg}, variant_dir='debug')
SConscript('SConscript', exports={'env': opt}, variant_dir='release')

then in the SConscript Import('env') will get dbg the first time and opt the second time. This also works for exporting/importing anything else you like, not just env.

See Export() and SConscript() in the man page for more info.