I’ve done something like this before to call Haskell from C++ (in [0]), so that I could build my GUI using Qt. It worked pretty well, except that I ran into various difficult-to-resolve linking problems on both Windows and Linux. After a year or two of trying to maintain it, I gave up and switched to a protocol where both sides pass JSON over stdin/stdout. This particular piece of software doesn’t require a huge amount of communication or shared data, so it works well enough.

The really nice thing about the original interop code, though, is that GHC’s new WASM backend uses essentially the same foreign function interface to export functions to JavaScript. So with only some minor modifications, I was able to get the same program working on a webpage [1], which I think is pretty cool.

[0] https://github.com/bradrn/brassica, and see in particular the old version of https://github.com/bradrn/brassica/blob/93d4353c5736018ec094...

[1] At the risk of DDOS’ing my poor little home server: https://bradrn.com/brassica/