Re[2]: [Haskell-cafe] C++ interface with Haskell
Hello Miguel,
Friday, April 18, 2008, 7:06:07 PM, you wrote:
you may look into my freearc.org project
overall, nothing complex as far as you got it :) i use
ghc -c c_file.cpp
ghc --make main.hs c_file.o
in order to call from C++ to Haskell or vice versa you should define
function in C++ as having extern C linkage. i recommend you to
declare function in header file which is able to compile either in C++
mode (used in first step) or C mode (used in second step, when
compiling main.hs):
#ifdef __cplusplus
extern C {
#endif
void myfunc(void);
#ifdef __cplusplus
}
#endif
then you use either foreign import haskell statement to use C++ func
from haskell or foreign export for other way. i also recommend you
to use main procedure written in haskell and run from this procedure
your main C function - this is the simplest way to initialize Haskell
runtime system. that's all
Thanks,
I found on one site how to compile after creating the stub files with GHC:
First step:
ghc -c -ffi haskell_file.hs
Second step - here it is important to know and write where are the ghc
libraries:
gcc -I /usr/local/lib/ghc-5.04.3/include -c C_file.c
After that it is important to link my creted C_file with the stub file and
compile it:
ghc -no-hs-main -o C_file C_file.o haskell_file.o haskell_file_stub.o
The final result is C_file execution file...just enter C_file and the program
is running correctly.
This information: how to compile and to link C with Haskell and to
call a Haskell funtion from C was quite difficult.
But here is my result of googling throw the internet and to find something
usefull.
Next challange: link C++ with C and creating a usefull documentation and put
it online!
Ciao,
Miguel Lordelo.
On Fri, Apr 18, 2008 at 3:33 PM, Alfonso Acosta [EMAIL PROTECTED] 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 [EMAIL PROTECTED]:
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 [EMAIL PROTECTED]
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
Re[2]: [Haskell-cafe] C++ interface with Haskell
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 [EMAIL PROTECTED]:
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 [EMAIL PROTECTED]
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.
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Best regards,
Bulatmailto:[EMAIL PROTECTED]
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Re: Re[2]: [Haskell-cafe] C++ interface with Haskell
To threadjack a little bit, I've been interfacing haskell with c++. It gets awkward when the c++ structures use STL types like string and vector. Of course those are too complex for haskell to marshal to. What I've been doing is defining an XMarshal variant of the X c++ class, that uses plain c arrays. Then I marshal to that, and construct the c++ object properly from XMarshal in the c-c++ wrapper layer. On a few occasions, when the c++ class is really big and only has one STL member, I make a partially constructed c++ object, pass the array separately, and then construct the proper c++ class from the broken haskell generated one. Possibly dangerous as all get-out because I'm dealing with unconstructed c++ objects, but it seems to work. Passing back to haskell is easier since I can use *vec.begin(), which according to the internet should be safe because STL guarantees that vector contents are contiguous. I'm only saved by the fact that I don't have that many different kinds of classes to pass. This would be much more drudgery if I had more. Does anyone have a better solution or convention for marshalling c++ objects? I've also noticed warnings from g++ about hsc2hs's use of the OFFSETOF macro on c++ classes, but some googling of g++ mailing lists implied that it's harmless if you don't have virtual bases, and what sane person does, so I suppress it now :) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] C++ interface with Haskell
qdunkan: To threadjack a little bit, I've been interfacing haskell with c++. It gets awkward when the c++ structures use STL types like string and vector. Of course those are too complex for haskell to marshal to. What I've been doing is defining an XMarshal variant of the X c++ class, that uses plain c arrays. Then I marshal to that, and construct the c++ object properly from XMarshal in the c-c++ wrapper layer. On a few occasions, when the c++ class is really big and only has one STL member, I make a partially constructed c++ object, pass the array separately, and then construct the proper c++ class from the broken haskell generated one. Possibly dangerous as all get-out because I'm dealing with unconstructed c++ objects, but it seems to work. Passing back to haskell is easier since I can use *vec.begin(), which according to the internet should be safe because STL guarantees that vector contents are contiguous. I'm only saved by the fact that I don't have that many different kinds of classes to pass. This would be much more drudgery if I had more. Does anyone have a better solution or convention for marshalling c++ objects? I've also noticed warnings from g++ about hsc2hs's use of the OFFSETOF macro on c++ classes, but some googling of g++ mailing lists implied that it's harmless if you don't have virtual bases, and what sane person does, so I suppress it now :) Would someone like to summarise the current approaches to combining Haskell C++ on the Haskell wiki, even if just in bullet points? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
