How can I force the SConscript builder to change directory?

Question

currently I'm trying to port a million-sloc legacy project from dull .cmd scripts to SCons. Parts of it are VC++, others are Delphi. Creating SConscripts for the C++ pieces was a breeze.

To build the delphi part I've written a very simple builder which detects whether it is a program or library project. Calling the builder after chaining via SConscript makes scons to call dcc32 $subdir/project.dpr what misleads dcc32 to look for units in the current directory instead of the $subdir.

Is there a way to tell scons to enter the $subdir before executing commands residing in the sconscript or should I fix it within the builder?

Thank you in advance

Answer 1

SCons already changes to the directory of sub-directory SConscripts when reading them, so it looks like the problem is going to have to be fixed in the actual builder.

Once the scripts are parsed, and SCons is running the build commands, it stays in the top-level directory. Commands are then issued using path names relative to that top-level directory. The way to change this behavior is to use the chdir keyword in your Builder.

The example from the scons man page is as follows:

b = Builder(action='build < ${SOURCE.file} > ${TARGET.file}',
            chdir=1)
env = Environment(BUILDERS = {'MyBuild' : b})
env.MyBuild('sub/dir/foo.out', 'sub/dir/foo.in')

You need to specify the .file component as the use of chdir does not change the names passed to the builder, i.e. they are still relative to the top-level directory.