Error code E0724

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

#[ffi_returns_twice] was used on something other than a foreign function declaration.

Erroneous code example:

#![allow(unused)]
#![feature(ffi_returns_twice)]
#![crate_type = "lib"]

fn main() {
#[ffi_returns_twice] // error!
pub fn foo() {}
}

#[ffi_returns_twice] can only be used on foreign function declarations. For example, we might correct the previous example by declaring the function inside of an extern block.

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

fn main() {
extern "C" {
   #[ffi_returns_twice] // ok!
   pub fn foo();
}
}