Question

I have a C++ project builds with Scons. At first I have only the optimized version to compile, it works fine. Then I also need a debug version, then I add another environment for it. Here is the Scons code:

env = Environment()

opt = env.Clone(CCFLAGS=['-pthread', '-O3', '-Wall'])
opt_objs = opt.Glob('src/*.cpp')
prog = opt.Program('prog', opt_objs)

dbg = env.Clone(CCFLAGS=['-pthread', '-Wall', '-g', '-O0'])
dbg_objs = dbg.Glob('src/*.cpp')
dbg_prog = dbg.Program('dbg_prog', dbg_objs)

With this code, I ran into error:

scons: *** Two environments with different actions were specified for the same target: 
src/CometReadService.o

As you can see, those .o files targets created by opt.Glob(‘src/.cpp’) and dbg.Glob(‘src/.cpp’) exactly same name. By reading the document Multiple Construction Environments I know I can rename the object like “opt.Object(‘xxx-opt’, ‘xxx.c’)”, but however, it is Glob not Object. How can I solve this problem?

Answer 1

The scons manual describes how to use the VariantDir function (or argument when adding SConscripts) to set up different build directories. At its simplest, VariantDir separates the build output from the source files, but it can also be used to separate the build output of different environments.

env = Environment()

opt = env.Clone(CCFLAGS=['-pthread', '-O3', '-Wall'])
opt.VariantDir('gen-opt', 'src', duplicate=0)
opt_objs = opt.Glob('gen-opt/*.cpp')
prog = opt.Program('prog', opt_objs)

dbg = env.Clone(CCFLAGS=['-pthread', '-Wall', '-g', '-O0'])
dbg.VariantDir('gen-dbg', 'src', duplicate=0)
dbg_objs = dbg.Glob('gen-dbg/*.cpp')
dbg_prog = dbg.Program('dbg_prog', dbg_objs)

Using VariantDir can take some experimentation. For instance, note that the Glob argument has changed — without the duplicate=0 parameter, the default behavior is for VariantDir to duplicate the source files in the build directory.