[Haskell-beginners] Linking C++ in Cabal

[鲍凯文]

Hi,

Would it be possible to upload your full repo somewhere so people could see
everything and possibly reproduce this?

Thanks,

toz

On Mon, May 25, 2020 at 5:03 AM <beginners-request at haskell.org> wrote:

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>    1.  Linking C++ in Cabal (Leonhard Applis)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Sun, 24 May 2020 16:30:22 +0000
> From: Leonhard Applis <Leonhard.Applis at protonmail.com>
> To: "beginners at haskell.org" <beginners at haskell.org>
> Subject: [Haskell-beginners] Linking C++ in Cabal
> Message-ID:
>
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>
> Hello,
>
> I want to use a foreign C++ Function in a Haskell Library, and the Library
> in a Haskell Program.
> The C++ function is separate in a file and I have a header file.
> I made a minimal reproducing repository.
>
> The closes I have found is this repository which wraps the c++ in c and
> makes a full library, needing a makefile etc.
> So while I think I'd get it working like that, it looks to be quite a lot
> to do for my simple task.
>
> the repository structure looks as follows:
>
> Projekt
>
> -   cpp-src
>
> -   some.cpp
> -   some.h
>
> -   lib-src
>
> -   CPPLib.hs
>
> -   program-src
>
> -   program.hs
>
> -   project.cabal
>
>
>
> And my (currently failing) project.cabal the following:
>
> cabal-version:  3.0
> name: cpp_lib
> [...]
> library
> exposed-modules: CPPLib
> other-extensions: ForeignFunctionInterface
> build-depends: base
> hs-source-dirs: lib-src
> default-language: Haskell2010
> include-dirs: ./cpp-src
> cxx-sources: ./cpp-src/some.cpp
> install-includes: ./cpp-src/some.h
>
> executable CPPApp
> main-is: program.hs
> default-language: Haskell2010
> build-depends: HaskellForeignCPP,
> base
> hs-source-dirs: program-src
>
> The some.cpp is trivial for this case lets assume its a function multiply
> :: Int -> Int -> Int, and both .cpp and .h are well-formed and don't have
> further dependencies.
>
> The library compiles fine, but when building the executable it fails
> telling me
>
> collect2: error: ld returned 1 exit status
> `gcc' failed in phase `Linker'. (Exit code: 1)
>
> Can someone help me out?
> I find very little documentation on this topic.
>
> I know there is Inline-CPP which would help as well, but I just very much
> like the idea of having a nice separate file and interface for modularity.
>
> best
> Leonhard
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