Understanding Rust Error E0781

Rust Error E0781 Summary

Rust error E0781 occurs when the C-cmse-nonsecure-call ABI is not used with function pointers. The ABI should be used by casting function pointers to specific addresses.

Example of Erroneous Code

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

fn main() {
    pub extern "C-cmse-nonsecure-call" fn test() {}
}

The Code Fix

The correct way to use the C-cmse-nonsecure-call ABI in Rust is by casting function pointers to specific addresses.

Correct Code Example

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

extern "C-cmse-nonsecure-call" fn test();

fn main() {
    let test_fn_ptr: unsafe extern "C-cmse-nonsecure-call" fn() = test;
    unsafe { test_fn_ptr() };
}

How to Avoid E0781

To avoid encountering Rust error E0781, always ensure that you are using the C-cmse-nonsecure-call ABI with function pointers. Cast the function pointers to specific addresses instead of using them directly as function signatures.

Summary

Remember, Rust error E0781 occurs when the C-cmse-nonsecure-call ABI is used incorrectly. You should use this ABI with function pointers, casting them to specific addresses. By adhering to this practice, you can easily avoid this error in your Rust programs.