Fiddle::Function.new

static VALUE
initialize(int argc, VALUE argv[], VALUE self)
{
    ffi_cif * cif;
    VALUE ptr, arg_types, ret_type, abi, kwargs;
    VALUE name = Qnil;
    VALUE need_gvl = Qfalse;
    int c_ret_type;
    bool is_variadic = false;
    ffi_abi c_ffi_abi;
    void *cfunc;

    rb_scan_args(argc, argv, "31:", &ptr, &arg_types, &ret_type, &abi, &kwargs);
    rb_iv_set(self, "@closure", ptr);

    if (!NIL_P(kwargs)) {
        enum {
            kw_name,
            kw_need_gvl,
            kw_max_,
        };
        static ID kw[kw_max_];
        VALUE args[kw_max_];
        if (!kw[0]) {
            kw[kw_name] = rb_intern_const("name");
            kw[kw_need_gvl] = rb_intern_const("need_gvl");
        }
        rb_get_kwargs(kwargs, kw, 0, kw_max_, args);
        if (args[kw_name] != Qundef) {
            name = args[kw_name];
        }
        if (args[kw_need_gvl] != Qundef) {
            need_gvl = args[kw_need_gvl];
        }
    }
    rb_iv_set(self, "@name", name);
    rb_iv_set(self, "@need_gvl", need_gvl);

    ptr = rb_Integer(ptr);
    cfunc = NUM2PTR(ptr);
    PTR2NUM(cfunc);
    c_ffi_abi = NIL_P(abi) ? FFI_DEFAULT_ABI : NUM2INT(abi);
    abi = INT2FIX(c_ffi_abi);
    ret_type = rb_fiddle_type_ensure(ret_type);
    c_ret_type = NUM2INT(ret_type);
    (void)INT2FFI_TYPE(c_ret_type); /* raise */
    ret_type = INT2FIX(c_ret_type);

    arg_types = normalize_argument_types("argument types",
                                         arg_types,
                                         &is_variadic);
#ifndef HAVE_FFI_PREP_CIF_VAR
    if (is_variadic) {
        rb_raise(rb_eNotImpError,
                 "ffi_prep_cif_var() is required in libffi "
                 "for variadic arguments");
    }
#endif

    rb_iv_set(self, "@ptr", ptr);
    rb_iv_set(self, "@argument_types", arg_types);
    rb_iv_set(self, "@return_type", ret_type);
    rb_iv_set(self, "@abi", abi);
    rb_iv_set(self, "@is_variadic", is_variadic ? Qtrue : Qfalse);

    TypedData_Get_Struct(self, ffi_cif, &function_data_type, cif);
    cif->arg_types = NULL;

    return self;
}