Error code E0776

Note: this error code is no longer emitted by the compiler.

#[cmse_nonsecure_entry] functions require a C ABI

Erroneous code example:

#![feature(cmse_nonsecure_entry)]

#[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".