SCons: modify intermediate builder calls

Question

Is it possible to change the calls to intermediate builders, e.g. by passing a target prefix, to avoid environment conflicts?

As an example, suppose you want to use a source file for two different libraries using different compiler macros like this:

env.Library('libraryA', 'source.c', CCFLAGS=['-DCONFIG_X'])
env.Library('libraryB', 'source.c', CCFLAGS=['-DCONFIG_Y'])

SCons detects a conflict, because the Library-Builder invokes the Object-Builder to compile the source file first with different CCFlags.

The obvious solution is to split the compilation from the linking, like this:

objectA = env.Object('objectA', 'source.c', CCFLAGS=['-DCONFIG_X'])
objectB = env.Object('objectB', 'source.c', CCFLAGS=['-DCONFIG_y'])
env.Library('libraryA', objectA)
env.Library('libraryB', objectB)

I was wondering if there is a more elegant way, which would be especially useful if there are multiple files used as source.

Thanks!

Answer 1

This could be achieved using the SCons VariantDir() function, which will place the build targets in a subdirectory.

Here's an example:

VariantDir('buildA', '.', duplicate=0)
VariantDir('buildB', '.', duplicate=0)

env.Library('libraryA', 'buildA/source.c', CCFLAGS=['-DCONFIG_X'])
env.Library('libraryB', 'buildB/source.c', CCFLAGS=['-DCONFIG_Y'])

This will build a different version of source.c in both buildA and buildB. Although the actual source.c source file is not in those build directories, you refer to it as if it was, so SCons knows where to put the output.

There's a better description for the VariantDir() function in the SCons man pages.

Answer 2

VariantDir() is the right general answer, but for simple cases you can use OBJPREFIX to put the objs for a given target in a subdir or just make them unique.

env.Library('libraryA', 'source.c', CCFLAGS=['-DCONFIG_X'], OBJPREFIX='libA-')