FFI question -- was: [Haskell-cafe] New slogan for haskell.org

Duncan Coutts duncan.coutts at worc.ox.ac.uk
Wed Dec 19 22:41:21 EST 2007

On Wed, 2007-12-19 at 19:07 -0800, Don Stewart wrote:

> There are three approaches, depending on the size of your project.
>     Write your ow FFI decls manually.
>         - Good when you have a small job
>         - and the C types are simple
>         - example:
>             strlen
>     Use hsc2hs:
>         - good for more complex C code. Scales nicely. But a bit tedious.
>         - examples: 
>             pcre.h
>             X11.h
>     Use c2hs:
>         - more automated than hsc2hs
>         - less common

The latest version is available on hackage :-)

>         - scriptable
>         - examples:
>             gtk2hs
> I use hsc2hs mostly.

The main advantage of c2hs over hsc2hs is that c2hs generates the
correct Haskell types of foreign imports by looking at the C types in
the header file. This guarantees cross language type safety for function
calls. It also eliminates the need to write foreign imports directly
which saves a lot of code. hsc2hs provides no help for writing function

The main disadvantage of c2hs compared to hsc2hs is that c2hs's support
for marshaling structures is less than stellar while hsc2hs is pretty
good at that.

In gtk2hs we use both. We use c2hs for all function calls and we use
hsc2hs to help us write Storable instances for a few structures.

Both are supported by Cabal.


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