scons not respecting variant_dir with object files - scons

Question

For simplicity sake, I'm able to reproduce this problem I'm having with the following example...
I currently have two files, a SConstruct and a SConscript.
My directory tree is as follows:
- .
- SConstruct
- build (dir)
- dir1 (dir)
- mysrc.cpp
- proj (dir)
- SConscript
Here is the contents of my SConstruct:
SConscript('dir1/proj/SConscript', variant_dir='build/out', duplicate=0)
Here is the contents of dir1/proj/SConscript:
src = Dir('.').srcnode().abspath + '/../mysrc.cpp'
StaticLibrary('mylib', src)
When I run scons at my root directory, I see the following output
g++ -o dir1/mysrc.o -c dir1/mysrc.cpp
ar rc build/out/libmylib.a
The ar command looks great, it outputs to the variant_dir, which is build/out. The problem here is the output location of mysrc.o. It goes to dir1 instead of build/out. Why does this happen?

Answer 1

You need to specify paths to source files as though they are sitting in the variant directory path.
Change your top level SConstruct to this...
SConscript('dir1/proj/SConscript', variant_dir='build/out', src_dir='dir1', duplicate=0)
And change your dir1/proj/SConscript to this...
src = Dir('.').srcnode().abspath + '/../../build/out/mysrc.cpp'
StaticLibrary('mylib', src)
Then when you run, you will see the following.
>> scons --version
SCons by Steven Knight et al.:
script: v2.3.6.rel_2.3.5:3347:d31d5a4e74b6[MODIFIED], 2015/07/31 14:36:10, by bdbaddog on hpmicrodog
engine: v2.3.6.rel_2.3.5:3347:d31d5a4e74b6[MODIFIED], 2015/07/31 14:36:10, by bdbaddog on hpmicrodog
engine path: ['/usr/lib/scons/SCons']
Copyright (c) 2001 - 2015 The SCons Foundation
>> tree
.
├── dir1
│   ├── mysrc.cpp
│   └── proj
│   └── SConscript
└── SConstruct
2 directories, 3 files
>> scons
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
g++ -o build/out/mysrc.o -c dir1/mysrc.cpp
ar rc build/out/proj/libmylib.a build/out/mysrc.o
ranlib build/out/proj/libmylib.a
scons: done building targets.
>> tree
.
├── build
│   └── out
│   ├── mysrc.o
│   └── proj
│   └── libmylib.a
├── dir1
│   ├── mysrc.cpp
│   └── proj
│   └── SConscript
└── SConstruct
5 directories, 5 files