Re: [Haskell-cafe] Wrapping a C++ library

Arjun, I'm not an expert in writing Haskell binding but pretty much experienced in C/low-level stuff. You shouldn't force compilation of .c files with g++. Instead, you should keep your wrapping functions as extern "C" and place their implementation in .cpp file (which of course should be compiled with g++). Don't forget to link to C++ runtime library (-lstdc++). There is also a wiki page[1] that describes how to call C++ from Haskell. Best regards, Alexey [1]: https://wiki.haskell.org/CPlusPlusFromHaskell 2015-01-26 23:27 GMT+02:00 Arjun Comar :

Richard, If you create a straight C header that's able to call into the C++ library then what you're trying to do will work. This is the standard (though frustrating) approach to using C++ libraries within Haskell. I can send you an example cabal file for building the Haskell code against the C headers and archives if you'd like. There isn't much more to it than what you're already doing though. The key is that the headers have to be pure C and you have to force cabal to build the C code with g++ (since the implementing .c files will necessarily make C++ calls).

Thanks, Arjun

On Mon, Jan 26, 2015 at 11:29 AM, Donn Cave wrote:

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Quoth Richard Lewis , ...

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There's a specific question here which goes something like: how do I get hsc2hs to compile code that uses STL headers?

For me, that would be the first thing to fix. Use #ifdef __cplusplus, or just reorganize, so the hsc2hs-generated files are just C. You wrote your wrapper library for the C++ part, and if the callers need to be C++ it kind of defeats the purpose.

From there, I would have guessed "extra-libraries: stdc++" would do it, (assuming you have also arranged to get your wrapper library in there), but I'm no cabal expert. I use C++ more or less like you're doing, so there's hope, but I haven't gotten around to the cabal part of the exercise.

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