1 The `ffi_pure` attribute was used on a non-foreign function.
3 Erroneous code example:
13 The `ffi_pure` attribute can only be used on foreign functions which do not have
14 side effects or infinite loops:
21 pub fn strlen(s: *const i8) -> isize;
26 You can find more information about it in the [unstable Rust Book].
28 [unstable Rust Book]: https://doc.rust-lang.org/unstable-book/language-features/ffi-pure.html