ffi_status ffi_prep_cif_var(ffi_cif *cif, ffi_abi abi, unsigned int nfixedargs, unsigned int ntotalargs, ffi_type *rtype, ffi_type **atypes)
ffi_status ffi_prep_closure_loc(ffi_closure *closure, ffi_cif *cif, void(*fun)(ffi_cif *, void *, void **, void *), void *user_data, void *codeloc)