[Haskell-cafe] make an PrimMonad-wrapped FFI call

Hello haskellers, I'm writing FFI bindings to C library which uses some allocations across functions call, for example: int *alloc_buf(void); void free_buf(int *); So I need to use newForeignPtr to make sure buffer will be free'd when all pointers to it get collected. But what if I want to do this in PrimMonad (say, ST) and not IO (returned by newForeignPtr)? Thanks.