On Sat, 2010-12-11 at 16:23 +0100, Erik Hesselink wrote:
Hi,
I'm trying to write a Storable instance for timespec using c2hs. Since timespec is defined something like:
struct timespec { time_t tv_sec; long tv_nsec; };
I've defined the following in Haskell:
#include
#c typedef struct timespec timespec_t; #endc
data TimeSpec = TimeSpec { seconds :: CTime , nanoseconds :: CLong }
instance Storable TimeSpec where peek t = TimeSpec <$> {#get timespec_t->tv_sec #} t <*> {#get timespec_t->tv_nsec#} t ...
However, this fails to compile. For tv_sec, c2hs generates "peekByteOff ptr 0 :: IO CLong" instead of "IO CTime". Why is this? Am I doing something wrong, or is there a bug/missing feature in c2hs?
It's because c2hs can see that time_t is in fact a typedef for long, and long translates to CLong. What is missing is a way to tell c2hs that we want to translate certain C typedefs to specific Haskell types, and not to chase the typedef chain all the way down to a primitive type. Duncan