I found the error [HklFactory 0xb7772920,HklFactory 0xb7772a6c,HklFactory 0xb7772a98,HklFactory 0xb7772ac4,HklFactory 0xb7772bf8,HklFactory 0xb7772ef8,HklFactory 0xb77734f0,HklFactory 0xb7773524,HklFactory 0xb77736c0,HklFactory 0xb7773784,HklFactory 0xb77738a8,HklFactory 0xb77738dc,HklFactory 0xb7773908,HklFactory 0xb77739cc] ["TwoC","E4CH","SOLEIL MARS","E4CV","K4CV","E6C","SOLEIL SIRIUS KAPPA","K6C","PETRA3 P09 EH2","SOLEIL SIRIUS TURRET","SOLEIL SIXS MED2+3","SOLEIL SIXS MED1+2","SOLEIL SIXS MED2+2","ZAXIS"] the signature of the C methode was wrong Ptr HklFactory -> HklFactory foreign import ccall unsafe "hkl.h hkl_factory_name_get" c_hkl_factory_name_get :: HklFactory -> IO CString thanks for your help ;)