i use green-card with ghc's FFI export to sth like

Haskell -----> C ------> Haskell

the program is just arithmatic operations. the program "seg fault" in the callback from C to Haskell. anyone whether it is a bug?

There aren't any known bugs, but there are many known pitfalls. You'll need to give us more information, at least: the code that causes the crash (preferably a small example), the exact GHC command lines used to compile it, your GHC version, your machine and OS version. Cheers, Simon