# Error code E0778

The `instruction_set` attribute was malformed.

Erroneous code example:

    #![feature(isa_attribute)]

    #[instruction_set()] // error: expected one argument
    pub fn something() {}
    fn main() {}

The parenthesized `instruction_set` attribute requires the parameter to be specified:

    #![allow(unused)]
    #![feature(isa_attribute)]

    fn main() {
    #[cfg_attr(target_arch="arm", instruction_set(arm::a32))]
    fn something() {}
    }

or:

    #![allow(unused)]
    #![feature(isa_attribute)]

    fn main() {
    #[cfg_attr(target_arch="arm", instruction_set(arm::t32))]
    fn something() {}
    }

For more information see the `instruction_set` attribute section of the Reference.