Interfacing Haskell and C++

Question

I'd like to call some Haskell functions in a c++ program.

In order to do so, i have applied these instructions and adapted them to my code and system.

What I have for the moment is the following:

Main.cpp
Shared header and cpp files
makefile
cpp/
- some cpp and header files
haskell/
- hello.hs

The make file is the following:

CPP_SOURCES = main.cpp textures.cpp cpp/game.cpp \
cpp/piece.cpp cpp/factories.cpp cpp/utils.cpp
HASKELL_SOURCES = haskell/hello.hs

all: main; ./main

main: $(CPP_SOURCES) HaskellPart.o; g++ \
    -lsfml-graphics \
    -lsfml-window \
    -lsfml-system \
    -I/usr/lib/ghc/include \
    -liconv \
    -I/usr/lib/ghc/ghc-8.0.1/include \
    -L/usr/lib/ghc/ghc-8.0.1 \
    -L/usr/lib/ghc/rts \
    -lHSrts \
    -L/usr/lib/ghc/base-4.9.0.0 \
    -lHSbase-4.9.0.0 \
    -L/usr/lib/ghc/ghc-prim-0.5.0.0 \
    -lHSghc-prim-0.5.0.0 \
    -L/usr/lib/ghc/integer-gmp-1.0.0.1 \
    -lHSinteger-gmp-1.0.0.1 \
    -lHSghc-prim-0.5.0.0 \
    -fno-stack-protector \
    -Wall \
    -o main $(CPP_SOURCES) haskell/hello.o

HaskellPart.o: $(HASKELL_SOURCES); ghc -fforce-recomp -fPIC $(HASKELL_SOURCES)

clean: ; rm -rf main && rm -rf haskell/*.o && \
rm -rf haskell/*.hi && rm -rf haskell/*_stub.h

What I have done is:

add -I/usr/lib/ghc/include to allow g++ to find HsFFI.h
update the librairies paths
add -fPIC to the ghc arguments to avoid symbol errors.

However, I end up with the following output:

    $ make
ghc -fforce-recomp -fPIC haskell/hello.hs
[1 of 1] Compiling Hello            ( haskell/hello.hs, haskell/hello.o )
g++ \
-lsfml-graphics \
-lsfml-window \
-lsfml-system \
-I/usr/lib/ghc/include \
 -liconv \
-L/usr/lib/ghc/rts \
-lHSrts \
-L/usr/lib/ghc/base-4.9.0.0 \
-lHSbase-4.9.0.0 \
-L/usr/lib/ghc/ghc-prim-0.5.0.0 \
-lHSghc-prim-0.5.0.0 \
-L/usr/lib/ghc/integer-gmp-1.0.0.1 \
-lHSinteger-gmp-1.0.0.1 \
-lHSghc-prim-0.5.0.0 \
 -fno-stack-protector \
 -Wall \
 -o main main.cpp textures.cpp cpp/game.cpp cpp/piece.cpp cpp/factories.cpp cpp/utils.cpp haskell/hello.o
/tmp/ccHPRuDY.o: In function `main':
main.cpp:(.text+0x358): undefined reference to `hs_init'
main.cpp:(.text+0x375): undefined reference to `hs_exit'
haskell/hello.o: In function `sRs_info':
/tmp/ghc9fcb_0/ghc_7.o:(.text+0x2e): undefined reference to `newCAF'
/tmp/ghc9fcb_0/ghc_7.o:(.text+0x3e): undefined reference to `stg_bh_upd_frame_info'
/tmp/ghc9fcb_0/ghc_7.o:(.text+0x54): undefined reference to `ghczmprim_GHCziCString_unpackCStringzh_closure'
/tmp/ghc9fcb_0/ghc_7.o:(.text+0x5d): undefined reference to `stg_ap_n_fast'
/tmp/ghc9fcb_0/ghc_7.o:(.text+0x96): undefined reference to `newCAF'
/tmp/ghc9fcb_0/ghc_7.o:(.text+0xa6): undefined reference to `stg_bh_upd_frame_info'
/tmp/ghc9fcb_0/ghc_7.o:(.text+0xbc): undefined reference to `base_SystemziIO_putStrLn_closure'
/tmp/ghc9fcb_0/ghc_7.o:(.text+0xc5): undefined reference to `stg_ap_p_fast'
haskell/hello.o: In function `helloFromHaskell':
(.text+0xd8): undefined reference to `rts_lock'
haskell/hello.o: In function `helloFromHaskell':
(.text+0xee): undefined reference to `base_GHCziTopHandler_runIO_closure'
haskell/hello.o: In function `helloFromHaskell':
(.text+0xf9): undefined reference to `rts_apply'
haskell/hello.o: In function `helloFromHaskell':
(.text+0x10f): undefined reference to `rts_evalIO'
haskell/hello.o: In function `helloFromHaskell':
(.text+0x122): undefined reference to `rts_checkSchedStatus'
haskell/hello.o: In function `helloFromHaskell':
(.text+0x12e): undefined reference to `rts_unlock'
haskell/hello.o: In function `stginit_export_Hello_zdfstableZZC0ZZCmainZZCHelloZZChelloFromHaskell':
ghc_3.c:(.text+0x144): undefined reference to `foreignExportStablePtr'
haskell/hello.o: In function `sRs_closure':
/tmp/ghc9fcb_0/ghc_7.o:(.data+0x40): undefined reference to `stg_IND_STATIC_info'
haskell/hello.o: In function `rHM_closure':
/tmp/ghc9fcb_0/ghc_7.o:(.data+0x60): undefined reference to `ghczmprim_GHCziTypes_TrNameS_static_info'
haskell/hello.o: In function `rI0_closure':
/tmp/ghc9fcb_0/ghc_7.o:(.data+0x70): undefined reference to `ghczmprim_GHCziTypes_TrNameS_static_info'
/tmp/ghc9fcb_0/ghc_7.o:(.data+0x80): undefined reference to `ghczmprim_GHCziTypes_Module_static_info'
haskell/hello.o: In function `SRD_srt':
/tmp/ghc9fcb_0/ghc_7.o:(.data.rel.ro+0x0): undefined reference to `ghczmprim_GHCziCString_unpackCStringzh_closure'
/tmp/ghc9fcb_0/ghc_7.o:(.data.rel.ro+0x8): undefined reference to `base_SystemziIO_putStrLn_closure'
collect2: error: ld returned 1 exit status
makefile:17: recipe for target 'main' failed
make: *** [main] Error 1

Any idea of what I am doing wrong ?

Thank you!

EDIT :

According to n.m answer, I changed the order of g++ arguments. Here's the new makefile:

CPP_SOURCES = main.cpp textures.cpp cpp/game.cpp cpp/piece.cpp cpp/factories.cpp cpp/utils.cpp
HASKELL_SOURCES = haskell/hello.hs
CFLAGS = -Wall -g -fno-stack-protector

all: main; ./main

main: $(CPP_SOURCES) HaskellPart.o; g++ \
    $(CFLAGS) -o main $(CPP_SOURCES) haskell/hello.o \
    -lsfml-graphics \
    -lsfml-window \
    -lsfml-system \
    -I/usr/lib/ghc/include \
    -liconv \
    -I/usr/lib/ghc/ghc-8.0.1/include \
    -L/usr/lib/ghc/ghc-8.0.1 \
    -L/usr/lib/ghc/base-4.9.0.0 \
    -lHSbase-4.9.0.0 \
    -L/usr/lib/ghc/ghc-prim-0.5.0.0 \
    -lHSghc-prim-0.5.0.0 \
    -L/usr/lib/ghc/integer-gmp-1.0.0.1 \
    -lHSinteger-gmp-1.0.0.1 \
    -lHSghc-prim-0.5.0.0 \
    -L/usr/lib/ghc/rts \
    -lHSrts \

HaskellPart.o: $(HASKELL_SOURCES); ghc -fforce-recomp -fPIC $(HASKELL_SOURCES)

clean: ; rm -rf main && rm -rf haskell/*.o && rm -rf haskell/*.hi && rm -rf haskell/*_stub.h

But it raised another error:

/usr/bin/ld: /usr/lib/ghc/rts/libHSrts.a(Itimer.o): undefined reference to symbol 'timer_settime@@GLIBC_2.3.3'

According to this thread, I added -lrt but got:

/usr/bin/ld: /usr/lib/ghc/rts/libHSrts.a(Linker.o): undefined reference to symbol 'dlsym@@GLIBC_2.2.5'

So according to this thread I added -ldl and now it's a big mess...

EDIT : BOUNTY

Guys I'm adding a bounty spending a large proportion of my low amount of reputation because I can't manage to make this work and really need this.

This is for a school related project but I have to precise that this is not cheating as subject only says: "write a large program in c++ and write the same program in haskell".

Making a common graphical interface for both programs is my decision and is out of the scope of the coursework.

Beside that, I think there a lack of documentation on this subject on internet, my teacher told me he never managed to do it so it would be helpful to have a constructed answer on the configuration of g++ with Haskell Foreign Export.

Thanks you for your help.

You have removed the last -lHSghc-prim-x.y.z parameter. Please consider restoring it, despite having another -lHSghc-prim-x.y.z upper in the list. — n. m. could be an AI, Mar 23 '17 at 13:40
Done. I edited my post with the new output, but it look identical. Thanks — Maxime VAST, Mar 23 '17 at 13:48
Just noticed you have all the libraries before all the objects/source files in your compilation command. **This is wrong and won't work**. See [this question and answer](http://stackoverflow.com/questions/45135/why-does-the-order-in-which-libraries-are-linked-sometimes-cause-errors-in-gcc). I also think you need to move HSrts down the chain of libraries in the link line. It probably should be the last library in the list. — n. m. could be an AI, Mar 26 '17 at 06:14
If you really need this to work, I highly recommend you write a C wrapper of the functions you really need. Then, it is relatively easier to call Haskell from C and then C++ from C (there will be more examples online of the former, and the latter it not. very difficult). — Alec, Mar 27 '17 at 15:49
@alec Using C would introduce a third language and I'm not allowed to. Moreover, it must be possible to achieve what I want by compiling Haskell and c++ together. I can't believe that it hasn't been done. I'm sure having a constructed answer on this thread would help others. — Maxime VAST, Mar 29 '17 at 16:34
@MaximeVAST This sort of thing tends to get hairy (source: I did this a couple months ago with Haskell/Java). Perhaps you would be willing to rephrase your question? Right now, you don't really have an [MVCE](https://stackoverflow.com/help/mcve). It would maybe be a good idea to include a minimal Haskell/C++ program that isn't working - that way we have _something_ to try to fix. Right now, you are the only person who can iterate. — Alec, Mar 29 '17 at 16:42
@alec. Got it ! here's the MVCE question: [link](http://stackoverflow.com/questions/43100934/calling-haskell-from-c) — Maxime VAST, Mar 29 '17 at 18:06
Link to my answer on your second version of this question. http://stackoverflow.com/a/43107962/7720738 — James Burton, Mar 30 '17 at 03:39

score 4 · Accepted Answer · answered Mar 30 '17 at 03:42

Tried just linking to my answer on your other version of this question but it decided to automatically make it a comment... Not particularly helpful because people who find this thread in the future might just see it as unanswered so I'll paste the full answer instead.

Not sure whether that's actually in your file or whether it's just in the version you put in your question but "// hello.hs" won't compile. Comments are -- in Haskell not //.

Anyway on to the interesting part...

First you need to import the HsFFI.h header file into your C++ code.

#include <iostream>
#include "Hello_stub.h"
#include <HsFFI.h>

Then use ghc to link the files after compiling them. Open a command prompt / terminal and navigate the directory containing your C++ and Haskell files. Then run the following commands:

ghc -c -XForeignFunctionInterface -O hello.hs
g++ -c -O main.cpp -I "C:\Program Files\Haskell Platform\7.10.3\lib\include"                         
ghc -no-hs-main hello.o main.o -lstdc++

The filepath in the second command is to the directory containing the HsFFI.h file.

Running main then outputs:

Hello from C++
Hello from Haskell

Interfacing Haskell and C++

1 Answers1

Linked