[Scons-users] Changing VariantDir in an SConscript file

[Bill Deegan]

the lib_b should have been:
lib_B = env_B.Library('Build/B/lib_B', ['Build/B/src/common.c', 'Build/B/
src/impl_B.c'])

(Thanks to mwichmann for pointing that out... need more coffee apparently..)

On Mon, Nov 15, 2021 at 11:38 AM Bill Deegan <bill at baddogconsulting.com>
wrote:

> Luke,
>
> VariantDir()'s seem to be one of the harder to grasp concepts in SCons so
> you're in good company.
> Assuming your Library() statements are in the same SConscript, you'd need
> to change them as follows
>
> lib_A = env_A.Library('Build/A/lib_A', ['Build/A/src/common.c', 'Build/A/
> src/impl_A.c'])
> lib_B = env_B.Library('Build/B/lib_B', ['Build/A/src/common.c', 'Build/A/
> src/impl_B.c'])
>
> Just adding a VariantDir() to an Environment() doesn't do anything to any
> builders you use with that environment.
>
> All you're doing with any VariantDir() statement is telling SCons that for
> example Build/A should be treated as if it was '.'.
> So any files you reference relative to Build/A, if they don't exist in
> Build/A, SCons should also look in .
>
> So for Build/A/src/common.c SCons should first look at that location, then
> it should look at ./src/commmon.c
>
> Is that any clearer?
> -Bill
>
>
> On Mon, Nov 15, 2021 at 9:54 AM Luke Tunmer <luke.tunmer at gmail.com> wrote:
>
>> Hi all,
>>
>> I'm trying to understand why calling VariantDir on my environment within
>> an SConstript file doesn't do what I thought it would. I suspect it's my
>> understanding that is broken, and if so, I'm looking for advice for how to
>> do this properly.
>>
>> My top level SConstruct file started the ball rolling with a variant_dir
>> that encapsulates all the different configurations that this system can be
>> built to ensure each configuration is built into a unique build folder
>> location (I turn duplicate off).
>>
>> Deep down in the tree in a particular SConscript file I need to compile
>> some C files two different ways which target the C compiler optimizer for
>> the particular CPU on which it will run (the embedded system is a multicore
>> one with at least 5 different CPU types). Some of these C files will be
>> running on different cores.
>>
>> I thought I could clone the environment two ways and modify the
>> VariantDir of each:
>>
>> Import('env')
>>
>> env_A = env.Clone()
>> env_A.VariantDir('build/A', '.', duplicate=0)
>> # add various CC flags to env_A
>>
>> env_B = env.Clone()
>> env_B.VariantDir('build/B', '.', duplicate=0)
>> # add different CC flags to env_B
>>
>> And then I would like to be able to specify the two different libraries
>> that need to be built at this level in the tree:
>>
>> lib_A = env_A.Library('lib_A', ['src/common.c', 'src/impl_A.c'])
>> lib_B = env_B.Library('lib_B', ['src/common.c', 'src/impl_B.c'])
>>
>> and then common.c will be compiled two ways into different build folders,
>> and the appropriate one included in each library. However, the change to
>> the VariantDir of each environment seems to make no difference at all: it
>> uses the build folder specified right at the top of the tree for both the
>> .o files and for the .lib files that it makes.
>>
>> Any help in my understanding of how VariantDir is supposed to work, and
>> what it is actually doing is appreciated. Or, of course, any information on
>> the proper way to achieve this result would be great.
>>
>> Regards,
>> Luke
>>
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>>
>
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