How to Use Haskell's Stack Build Tool to Export a Library to Be Consumed by C/C++?

Question

Suppose one is using the stackbuild tool to make a Haskell library (importing packages from Hackage, and so forth) to be used with a C/C++ project in which main is located in C/C++.

Supposing your project is named Lib.hs (which uses external libraries from hackage), is there a way to use stack to export your Lib.o, Lib.hi, and Lib_stub.h to be consumed by a C/C++ compiler like gcc or g++?

EDIT: A related question might be: "how can one use Stack as a build tool to be used with a Haskell & C/C++ project in which main is located in C/C++?

EDIT2: Upon reflection, one way to solve this problem would be to use Stack as usual, but migrate your C/C++ main function to Haskell. Is this the best way to do it? Are there huge performance costs to this or anything I should be aware of?

Answer 1

Stack can't really do this on its own.

There's support for generating so called "foreign libraries" added to Cabal, but it's not in a released version, yet. See commit 382143 This will produce a shared library that dynamically links against the dynamic versions of each Haskell package used.

You can build your package with stack and then after the fact you can assemble a single native library. In the Galua project we do this with a custom Setup.hs and a separate linking script.

The result of this linking process is that you get a standalone statically linked library suitable for inclusion in a C project: libgalua.a.

Do note that for creating standalone libraries on Linux suitable for being linked into a shared library that you'll need to recompile GHC to generate PIC static libraries (macOS does this by default).