use std::cell::Cell;
use std::ffi::c_char;
thread_local! { static CALLS: Cell<i32> = const { Cell::new(0) }; }
#[unsafe(no_mangle)]
pub extern "C" fn goose_init(_argc: i32, _argv: *mut *mut c_char) {
    CALLS.with(|calls| calls.set(100)); // this example's startup state only
}
/// Safety: length must point to a live, writable, aligned i64.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn hello_world(length: *mut i64) -> *const u8 {
    CALLS.with(|calls| calls.set(calls.get() + 1));
    const MESSAGE: &[u8] = b"Hello, world!";
    unsafe { *length = MESSAGE.len() as i64; }
    MESSAGE.as_ptr() // static bytes, not NUL-terminated
}
#[unsafe(export_name = "c_add")]
pub extern "C" fn add(a: i32, b: i32) -> i32 { a + b }

fn main() {
    goose_init(0,std::ptr::null_mut()); let mut length=0_i64;
    // SAFETY: length is a valid writable local; the result is static MESSAGE bytes.
    let pointer=unsafe {hello_world(&mut length)};
    let message=unsafe {std::slice::from_raw_parts(pointer,usize::try_from(length).unwrap())};
    assert_eq!(message,b"Hello, world!");assert_eq!(CALLS.with(Cell::get),101);
    use std::io::Write;let mut out=std::io::stdout().lock();out.write_all(message).unwrap();writeln!(&mut out).unwrap();
    writeln!(&mut out,"{}",add(20,22)).unwrap();
}