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

Donn, Arjun, Alexey, Ian, Thanks, all, for your suggestions. At Mon, 26 Jan 2015 08:29:24 -0800, Donn Cave wrote:

Quoth Richard Lewis , ...

...

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.

Yes, so it turns out the problem was that my wrapper .h was including one of the headers of the third party library which, in turn, was including vector. But I've managed to arrange it so that I don't need to include that third party header anymore so gcc can compile my translation unit without problems.

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.

The challenge with Cabal now is to get it to link my .a library with the libHSMyLibrary.a that GHC creates. It seems, from what I've read [1], that there is no Cabal hook into the linker so it may involve quite a bit of work in the Setup.hs file. I was just following up a suggestion [2] that (I think), if the .a file Cabal has created for my wrapper static library is in the same directory as, um, not sure what--output libHSMyLibrary.a? gcc working directory?--and if its name is of the form "libxxx.a", then it may be possible to add -lmylib to gcc's options, and gcc will pick it up. Anyway, I altered my Setup.hs to do this, putting libmylib.a in dist/build and dynamically adding /path/to/dist/build to the "extra-libraries" option, but nm still reports that the resulting libHSMyLibrary.a does not contain libmylib.a (or would it be mylib.o?). This might be a discussion for a new thread, however. The immediate problem of how to compile the C wrapper is now fixed. Richard [1] http://stackoverflow.com/questions/18543228/statically-linking-a-c-library-w... [2] https://www.haskell.org/pipermail/haskell-cafe/2006-June/016022.html