[Haskell-cafe] C++ interface with Haskell

[Bulat Ziganshin]

Hello Isaac,

Friday, April 18, 2008, 7:27:56 PM, you wrote:

absolutely true! it's required if you use new/delete and other things
supported by c++ RTS

> if you'd normally be linking using g++, you'll need (IIRC) -lstdc++ 
> added to linking-ghc's command line

> Alfonso Acosta wrote:
>> Although you could use gcc to link the code I wouldn't recommend it
>> (mainly for the problems you are currently having)
>> 
>> SImply call GHC to compile both the C and Haskell code. It will take
>> care of finding the headers and supplying the necessary linker
>> arguments.
>> 
>> ghc -ffi -c   foo.hs myfoo_c.c
>> 
>> BTW, you don't need to compile viaC
>> 
>> 2008/4/17 Miguel Lordelo <miguellordelo at gmail.com>:
>>> Well Isaac...I became now a little bit smarter then yesterday!!!
>>>
>>> I show you the example that I found and on which I?m working with.
>>>
>>> File: foo.hs
>>> module Foo where
>>>
>>> foreign export ccall foo :: Int -> IO Int
>>>
>>> foo :: Int -> IO Int
>>> foo n = return (length (f n))
>>>
>>> f :: Int -> [Int]
>>> f 0 = []
>>> f n = n:(f (n-1))
>>>
>>> To get the C wrapper you insert the following command:
>>> ghc -ffi -fvia-C -C foo.hs
>>>
>>>  After execution you will have these following additional files:
>>>
>>> foo.hc
>>> foo.hi
>>> foo_stub.c
>>> foo_stub.h
>>> foo_stub.o
>>>
>>> What I did next was to create a file named: myfoo_c.c, where I will call the
>>> foo function (implemented in Haskell).
>>>  (you can see this example on
>>> http://www.haskell.org/ghc/docs/latest/html/users_guide/ffi-ghc.html )
>>> But the problem is to compile with gcc (must I put any flag or whatever set
>>> something)
>>>
>>> The gcc output is:
>>> myfoo_c.c:2:19: error: HsFFI.h: No such file or directory
>>>
>>> I downloaded this header file from: (I know that is not the correct way, but
>>> it was the only idea that occurs at the moment)
>>> http://www.koders.com/c/fidD0593B84C41CA71319BB079EFD0A2C80211C9337.aspx
>>>
>>> I compiled again and the following return error appears:
>>> myfoo_c.c:(.text+0x1c): undefined reference to `hs_init'
>>> myfoo_c.c:(.text+0x31): undefined reference to `foo'
>>> myfoo_c.c:(.text+0x50): undefined reference to `hs_exit'
>>>  collect2: ld returned 1 exit status
>>>
>>> These functions are necessary to setup GHC runtime (see:
>>> http://www.haskell.org/ghc/docs/latest/html/users_guide/ffi-ghc.html )
>>>
>>> What I want to know is how to compile myfoo_c.c?! Is it with GCC or GHC?!
>>>
>>> Chears,
>>> Miguel Lordelo.
>>>
>>>
>>>
>>>
>>> On Wed, Apr 16, 2008 at 9:16 PM, Isaac Dupree <isaacdupree at charter.net>
>>> wrote:
>>>
>>>> perhaps
>>>>
>>>> haskell:
>>>> foreign export "foo_func" foo :: Int -> IO Int
>>>> -- I forget the rest of the syntax here
>>>>
>>>> C++:
>>>>
>>>> extern "C" {
>>>> int foo_func(int i);
>>>> }
>>>>
>>>> int some_cplusplus_function() {
>>>>  int bat = 3;
>>>>  int blah = foo_func(bat);
>>>>  return blah;
>>>> }
>>>>
>>>>
>>>> Is that all you need to do?
>>>>
>>>>
>>>> Miguel Lordelo wrote:
>>>>
>>>>>
>>>>>
>>>>> Hi all,
>>>>>
>>>>> Well...somehow I'm a beginner in Haskell. But actually my interest in
>>>>> Haskell will increase if it is possible to call a haskell function in
>>> C++.
>>>>> Something like GreenCard ( http://www.haskell.org/greencard/ )
>>> simplifying
>>>>> the task of interfacing Haskell programs to external libraries
>>> (usually).
>>>>> But is there also a task to interface a foreign language with Haskell,
>>> but
>>>>> calling Haskell functions. Or c2hs which is an interface generator that
>>>>> simplifies the development of Haskell bindings to C libraries.
>>>>>
>>>>> I want to know this, because in my company some guys are doing some
>>> testing
>>>>> with Frotran and MatLab and I want to show them the power of haskell and
>>> the
>>>>> software which we are using is implemented in C++ (there is the reason
>>> to
>>>>> make Haskel -> C++).
>>>>>
>>>>> I read somewhere that the only way for C++ calling a haskell function is
>>> to
>>>>> create a binding between Haskell and C and from C to C++, but a easy
>>> "Hello
>>>>> World" example was not there.
>>>>> Unfortunatelly I couldn't found anything usefull, like an complete
>>> example,
>>>>> or how to compile the code from haskell to C to C++.
>>>>>
>>>>> Can sombody help me, please :P
>>>>>
>>>>> Chears,
>>>>> Miguel Lordelo.
>>>>>
>>>>>
>>>>>
>>>>> ------------------------------------------------------------------------
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Haskell-Cafe mailing list
>>>>> Haskell-Cafe at haskell.org
>>>>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>>>>>
>>>>
>>>
>>> _______________________________________________
>>>  Haskell-Cafe mailing list
>>>  Haskell-Cafe at haskell.org
>>>  http://www.haskell.org/mailman/listinfo/haskell-cafe
>>>
>>>
>> 

> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe


-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin at gmail.com