[Scons-users] Modifying the provided environment in an emitter?

[Andrew C. Morrow]

Hi Bill -

That was a minimal example, to demonstrate my intent, but what I want to do
is a little more complex.

In one case, I want to run a transform over any arguments passed in to a
Program, SharedLibrary, etc. call:

If the user writes:

prog = env.Program(
    target="foo",
    source=[...],
    LIBS=[
        "thing/foo",
        "place/bar",
)

I want a chance to re-write the LIBS for these targets based on project
specific rules, so that this is as if the user wrote:

prog = env.Program(
    target="foo",
    source=[...],
    LIBS=[
        "thing/foo_actual_uglified_name",
        "place/bar_actual_uglified_name",
)


 Another example would be something like this:

    def compiling_target_emitter(target, source, env):
        targetbase = str(target[0].get_subst_proxy().filebase)
        targetbase = targetbase.upper() # possibly more complex
transformations in practice
        env.AppendUnique(CPPDEFINES=['COMPILING_' + targetbase])
        return target, source

Here, I want every SharedLibrary or LoadableModule to automatically have
COMPILING_$TARGET.filebase set in CPPDEFINES when it is built, as part of
managing symbol visibility, and I don't want every user who writes a
declaration for a library to know how to get it right, I want it to happen
automatically. Also, there doesn't seem to be a SHCPPDEFINES...

However, since it appears that all targets don't get a private env unless
there is an override in the declaration, that this approach may not be
viable.

Thanks,
Andrew

On Fri, Apr 21, 2017 at 7:00 PM, Bill Deegan <bill at baddogconsulting.com>
wrote:

> Andrew,
>
> I'm not sure why you wouldn't just do:
> env['LIBS'] = env.get('LIBS',[])
> env.AppendUnique('LIBS','foo')
>
> Why do this in the emitter, instead of in the environment?
>
> -Bill
>
>
> On Fri, Apr 21, 2017 at 2:29 PM, Andrew C. Morrow <
> andrew.c.morrow at gmail.com> wrote:
>
>>
>> Hi all -
>>
>> Is it legit to modify the passed in env in an emitter?
>>
>>     def add_lib_foo_emitter(target, source, env):
>>         libs = env.get('LIBS', [])
>>         libs.append('foo')
>>         env['LIBS'] = libs
>>         return (target, source)
>>
>>     def add_emitter(builder):
>>         base_emitter = builder.emitter
>>         new_emitter = SCons.Builder.ListEmitter([add_lib_foo_emitter,
>> base_emitter])
>>         builder.emitter = new_emitter
>>
>>     target_builders = ['Program', 'SharedLibrary', 'LoadableModule',
>> 'StaticLibrary']
>>     for builder in target_builders:
>>         add_emitter(env['BUILDERS'][builder])
>>
>> I've found myself wanting to do this with increasing frequency, but am
>> unclear on whether this is acceptable. It appears to work, but the
>> documentation doesn't seem to offer any clear guidance that I've found on
>> whether it is guaranteed to work. If so (which would be great!), am I
>> guaranteed that the modification of env is scoped only to the passed in
>> targets?
>>
>> Thanks,
>> Andrew
>>
>>
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>>
>>
>
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