Tell ocamlbuild where to find module - linker

Question

I have an OCaml project, for which I use ocamlbuild.
In this project, I have two subprojects, subproject1 and subproject2.
subproject2 needs to use a module called Module from subproject1.
To sum up, I have the following structure:
project/
|
|-- subproject1
| |
| |-- module.ml
|
|-- subproject2
|
|-- main.ml
If module.ml were located in subproject2, next to main.ml, I'd simply use the open directive in subproject2/main.ml:
(*subproject2/main.ml *)
open Module
But since module.ml is located in subproject1, how can I tell ocamlbuild to open subproject1/module.ml?

Answer 1

While I haven't found any straightforward way to include or directly link a source file, I've come up with a way to effectively include a module from a sibling directory.
Once again, here is the structure of the project:
project/
|
|-- subproject1
| |
| |-- module.ml
|
|-- subproject2
|
|-- main.ml
From the project directory, the following ocamlbuild command will compile the whole project, with subproject2/main.ml as target, and subproject2/_build/ as output build directory:
ocamlbuild -I subproject1 subproject2/_build/ subproject2/main.byte
The expected main.byte file will however be output as subproject2/_build/subproject2/main.byte, so manual link editing will be necessary to end up with the usual main.byte symlink in subproject2.
Since I like being able to use make, I wrote the following Makefile in subproject2/, so as to compile subproject2/ by simply running make from the inside, as make is supposed to work.
all:
# Move to project/
cd ..;\
# Run the ocamlbuild command
ocamlbuild -I subproject1 subproject2/_build/ subproject2/main.byte\
# Go back into subproject2
cd subproject2;\
# Try to remove the existing symlink, mute stderr, and continue on error
rm main.byte 2> /dev/null || true;\
# Create the desired symlink
ln -s _build/subproject2/main.byte main.byte