[Haskell-beginners] Linking C++ in Cabal - repository Link

[Leonhard Applis]

Ups, in my mailing list the links have disappeared.
Just in case:  


The minimal reproducing repository: 

https://github.com/Twonki/HaskellForeingCPPMinimal

The repository from Aditya Siram with C and makefile: 

https://github.com/deech/CPlusPlusBindings

best
Leonhard



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On Monday, May 25, 2020 2:00 PM, <beginners-request at haskell.org> wrote:

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> 1.  Linking C++ in Cabal (Leonhard Applis)
>     

> 

> 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:
> 51wOfngyX74dYjJRw6hibqw07vGHvvSYPD_f3f2-_F7hG0k0GwWf2Xv4g7LyeZNyn_vR28s6GIbd3e-78_TapNIEo_tJZ-2fTViOmkQYOnM=@protonmail.com
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> Content-Type: text/plain; charset="utf-8"
> 

> 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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