[Boost-build] Muktiple depoendent projects vs. boost build MkDir

From: Mat Marcus (mat-lists_at_[hidden])
Date: 2008-04-07 16:09:42

I am having some difficulty figuring out how to get boost build to do
my bidding. Perhaps someone here can help. I have to completely
separate project directory trees which I'll call tree1 and tree2. Each
of these trees has at least the following files at the top level. Here
is an abstracted picture of my directory structure:

tree1
  - project-root.jam
  - boost-build.jam
  - Jamfile.v2
  - deep hierarchy of subdirectories some of which contain there own
Jamfile.v2's

tree2 (optional, depends on tree1 relative location and artifacts)
  - project-root.jam
  - boost-build.jam
  - Jamfile.v2
  - deep hierarchy of subdirectories some of which contain there own
Jamfile.v2's

built_artifacts:
  - Build dir used by both tree1 and tree2 Jamfiles

tree2, if present, expects to be located as a peer to tree1 in the
directory structure. Furthermore, built artifacts (from either tree)
are to be located in built_artifacts. tree2 depends on some of the
artifacts in tree1. Users of tree1 can "build the world" by invoking
bjam when the working directory is tree1. Jamfiles in tree2 contain
relative references to projects in tree1.

Now I can pose my question.  I would like for users of tree2 to be
able to build both tree1 and tree2 by simply invoking bjam when the
working directory is set to tree2. In order to make this possible,
tree2/Jamfile.v2 contains a statement along the lines of build_project
../tree1 . This seems to work fine in case tree1 is already built. But
if a user sets the working directory to tree2 and invokes bjam when
the built_artifacts directory doesn't yet exist, then strange things
begin to happen. As far as I can tell, what happens is that first
tree1 is built successfully, but as boost build reaches the point
where it tries to create tree2 artifacts I receive errors such as:

MkDir1 ..\built_artifacts
A subdirectory or file ..\built_artifacts already exists.

    mkdir "..\built_artifacts"

...failed MkDir1 ..\built_artifacts...

If I run bjam again from the same location, the build continues
successfully for a while. After several invocations of bjam all
targets are built successfully.

In the past I've spent a bit of time debugging this (on mac, win,
cygwin), and it seems the issue relates to a combination of the fact
that mkdir returns an error code when it tries to create a directory
that already exists, and the fact that boost build asks for the same
dir to be created at two different points in the build process under
the above configuration.

For now I provide a thing wrapper script around bjam that will execute
it multiple times. But the error output doesn't make a good impression
on my library users so I'd really like to find a better solution. Can
anyone here advise me?

Thanks,
Mat