Error code E0724
#[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(); } }