CODEWITHSUNDEEP
chaskell
Elliot Gorokhovsky
Elliot Gorokhovsky

Reputation: 3762

Trying to export a Haskell lib for C

I copied the example code in the Haskell FFI guide as a first step to exporting my Haskell program as a C library, but can't get it to compile. I have 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))

This successfuly compiled to foo_stub.h and foo_stub.o. Here's foo_stub.h:

#include "HsFFI.h"
#ifdef __cplusplus
extern "C" {
#endif
extern HsInt foo(HsInt a1);
#ifdef __cplusplus
}
#endif

But then my C program didn't compile:

#include "foo_stub.h"
main() { foo(1); } // I realize this is probably wrong, and would also like advice on doing this part correctly, but note the error is not here.

error:

gcc foo.c
In file included from foo.c:1:0:
foo_stub.h:1:19: fatal error: HsFFI.h: No such file or directory
 #include "HsFFI.h"
                   ^
compilation terminated.

I assume I'm missing some header files or haven't pointed gcc to them correctly. I can provide more information if necessary. Any ideas on how to fix this?

Upvotes: 1

Views: 890

Answers (1)

crockeea
crockeea

Reputation: 21811

I found "HsFFI.h" at /usr/local/lib/ghc-7.10.2/include/HsFFI.h. You should be able to direct GCC to look there with the -I option. More information here.

Upvotes: 6

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