SConscript in different directory to source files

I'm building code with multiple environments, outputting to multiple target directories. The natural way to manage this seems to be with variant directories. So I might want to build the same set of files multiple times with different options and different VariantDirs. So I want to be able to have multiple SConscript files in different locations, all referring back to the same source directory.

One option I've tried is to do this:

SConstruct
src/test.cpp
src/magic/SConscript

This is my SConstruct:

env = Environment()

SConscript('src/magic/SConscript',
    variant_dir = 'build/src',
    src_dir = 'src',
    exports={'env':env},
    duplicate=0)

and this is src/magic/SConscript:

Import('env')

source = 'test.cpp'

env.Object(source)

I get this output:

scons: *** [build/src/magic/test.o] Source `src/magic/test.cpp' not found, needed by target `build/src/magic/test.o'.

This looks like both the variant_dir and src_dir are not being respected by Object, since neither mention magic at all.

Have I misunderstood how variant_dir/src_dir are meant to work, and what is the best way to build the same set of files with different targets?

Solution

Your file/folder hierarchy doesn't fit the build specification in your SConstruct/SConscript files. Note how file paths in SCons are usually relative to the location of the current SConscript, so:

source = 'test.cpp'
env.Object(source)

in src/magic/SConscript gets expanded to src/magic/test.cpp...which obviously doesn't exist. You could use ../test.cpp as filename, or move the SConscript one up from src/magic to the src folder directly.

Some further remarks:

1.) When you specify a path for the name of the SConscript file in the SConscript call:

SConscript('src/SConscript',
    variant_dir = 'build',
    exports={'env':env},
    duplicate=0)

SCons will automatically derive the src_dir argument from the path of the first argument.

2.) Please check out the chapter 14 "Hierarchical Builds" in the UserGuide ( http://www.scons.org/doc/production/HTML/scons-user.html ).