This is a small repo in which I'm trying to set up a realistic Haskell project and link FFI binaries (in this case Rust, but it could be anything) into it with minimal pain.
Resources used:
This pretty much just works, with a couple downsides:
- Whatever file actually includes the FFI library complains because "loading static libraries is not supported in this configuration".
I think this is purely a language server issue, as the build itself works.
This is being worked around by telling cargo to build both a dynamic and static library- but this may not be ideal;
in particular I'm unsure how to force it to statically link if both are available.
- The file must be linked from an abolute path, so the FFI target needs to be installed in a global place.
Output:
; cabal clean && cabal run
Resolving dependencies...
Build profile: -w ghc-9.0.2 -O0
In order, the following will be built (use -v for more details):
- haskellrustlink-0.1.0.0 (lib:extlib) (first run)
- haskellrustlink-0.1.0.0 (lib) (first run)
- haskellrustlink-0.1.0.0 (exe:demo) (first run)
Configuring library 'extlib' for haskellrustlink-0.1.0.0..
Preprocessing library 'extlib' for haskellrustlink-0.1.0.0..
Building library 'extlib' for haskellrustlink-0.1.0.0..
[1 of 2] Compiling Extlib.Internal ( extlib/Extlib/Internal.hs, /Users/jessica/projects/scratch/haskellrustlink/dist-newstyle/build/aarch64-osx/ghc-9.0.2/haskellrustlink-0.1.0.0/l/extlib/noopt/build/extlib/Extlib/Internal.o, /Users/jessica/projects/scratch/haskellrustlink/dist-newstyle/build/aarch64-osx/ghc-9.0.2/haskellrustlink-0.1.0.0/l/extlib/noopt/build/extlib/Extlib/Internal.dyn_o )
[2 of 2] Compiling Extlib ( extlib/Extlib.hs, /Users/jessica/projects/scratch/haskellrustlink/dist-newstyle/build/aarch64-osx/ghc-9.0.2/haskellrustlink-0.1.0.0/l/extlib/noopt/build/extlib/Extlib.o, /Users/jessica/projects/scratch/haskellrustlink/dist-newstyle/build/aarch64-osx/ghc-9.0.2/haskellrustlink-0.1.0.0/l/extlib/noopt/build/extlib/Extlib.dyn_o )
Configuring library for haskellrustlink-0.1.0.0..
Preprocessing library for haskellrustlink-0.1.0.0..
Building library for haskellrustlink-0.1.0.0..
[1 of 1] Compiling Lib ( src/Lib.hs, /Users/jessica/projects/scratch/haskellrustlink/dist-newstyle/build/aarch64-osx/ghc-9.0.2/haskellrustlink-0.1.0.0/noopt/build/Lib.o, /Users/jessica/projects/scratch/haskellrustlink/dist-newstyle/build/aarch64-osx/ghc-9.0.2/haskellrustlink-0.1.0.0/noopt/build/Lib.dyn_o )
Configuring executable 'demo' for haskellrustlink-0.1.0.0..
Preprocessing executable 'demo' for haskellrustlink-0.1.0.0..
Building executable 'demo' for haskellrustlink-0.1.0.0..
[1 of 1] Compiling Main ( app/Main.hs, /Users/jessica/projects/scratch/haskellrustlink/dist-newstyle/build/aarch64-osx/ghc-9.0.2/haskellrustlink-0.1.0.0/x/demo/noopt/build/demo/demo-tmp/Main.o )
Linking /Users/jessica/projects/scratch/haskellrustlink/dist-newstyle/build/aarch64-osx/ghc-9.0.2/haskellrustlink-0.1.0.0/x/demo/noopt/build/demo/demo ...
Hello, Haskell
Hello from Rust!
Hello through Rust
3 doubled is: 6The attempt was to get this to replicate a non-trivial project and quarantine the language server error.
app/Main.hs: The binary entry point. Depends onsrc/Lib.hs.src/Lib.hs: The library. Depends onextlib/Extlib.hs.extlib/Extlib.hs: A wrapper for the FFI layer to hide FFI types. Depends onextlib/Extlib/Internal.hs.extlib/Extlib/Internal.hs: The actual file that calls into the FFI binary.extlib/hello: The Rust library being FFI'd into.
extlib has its own library extlib entry in the Cabal file:
this uses the "convenience libraries" feature of Cabal.
- Force the Haskell binary to be statically linked.
- Make the build script put the Rust binary somewhere global but system independent for building.
- Make a test matrix including Windows so I can validate how that works.
Things I'd like to do, but may not be easily doable:
- Somehow work around the language server error without building a
cdylib.