On Tue, 2009-01-27 at 06:32 +0200, Eyal Lotem wrote:
I have encountered quite a bit of bugs in foreign bindings where "Int" was used in place of "Cint".
As far as I know, no foreign function should ever take a Haskell Int, only CInts.
Would it be possible to create an empty type-class of which various C-acceptable types are instances (e.g CInt, CString) but Haskell types aren't (Ints)?
The compiler does already know which types are valid in FFI calls. The problem perhaps is that Int is one of the allowed types, it's just that on the C side the corresponding type must be 'HsInt' and not 'int'. Unfortunately the hsc2hs tool provides no support for checking C <-> Haskell type consistency. In contrast, the c2hs tool can prevent these problems because it will generate the correct ffi import types given the C headers. Duncan