Error code E0776

#[cmse_nonsecure_entry] functions require a C ABI

Erroneous code example:

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

fn main() {
#[no_mangle]
#[cmse_nonsecure_entry]
pub fn entry_function(input: Vec<u32>) {}
}

To fix this error, declare your entry function with a C ABI, using extern "C".