SCons Dynamic Construction Variable

Question

I would like to have a dynamic environmental variable in SCons.

Example: Add -DFILE_NAME=file.c to the build command.

env['FILE_NAME'] = ['${str($TARGET).upper()}']
env.Append(CPPDEFINES={'FILE_NAME': '$FILE_NAME'})

I'm not sure if this is possible but the documentation with _concat, source or the older documentation for CCPDBFLAGS makes it seem like it might be.

Using SCons 3.1.1

Answer 1

This is actually a bug. A workaround is below.

import hashlib

env = Environment(platform='darwin')
env['CC'] = 'clang'

# env.Append(CPPDEFINES={'SOURCE': '$SOURCE'})
# env.Append(CPPDEFINES={'TARGET': '$TARGET'})

def fileHashGenerator(env, target, source):
    print("'%s' '%s' '%s'" % (env, target, source))
    if source:
        print("has source")

        fileHash = int(hashlib.sha1(source.path.encode()).hexdigest(), 16) % (10 ** 8)
        print(fileHash)
        h = (fileHash).to_bytes(8, byteorder='big').hex()
        print(h)
        return h
    else:
        print("No target", type(target))
    return 'NOTHING'

env['FILE_HASH'] = '${fileHashGenerator(__env__,TARGET,SOURCE)}'

# env.Append(CPPDEFINES={'FILE_HASH': '$FILE_HASH'})
env.Append(CPPFLAGS=['-DFILE_HASH=$FILE_HASH'])
env.Append(CPPFLAGS=['-DFILE_TARGET=${TARGET}'])
env.Append(CPPFLAGS=['-DFILE_SOURCE=$SOURCE'])
env['fileHashGenerator'] = fileHashGenerator

env.Program('main', ['main.c'])

Don't use CPPDEFINES, instead append it to CPPFLAGS. Thanks @bdbaddog for the assist in the SCons discord.