You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: strlen_on_c_strings.rs
    path of file: ./repos/rust-clippy/tests/ui
    
    the code of the file until where you have to start completion: #![warn(clippy::strlen_on_c_strings)]
#![allow(dead_code, clippy::manual_c_str_literals)]
#![feature(rustc_private)]
extern crate libc;

#[allow(unused)]
use libc::strlen;
use std::ffi::{CStr, CString};

fn main() {
    // CString
    let cstring = CString::new("foo").expect("CString::new failed");
    let _ = unsafe { libc::strlen(cstring.as_ptr()) };

    // CStr
    let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
    let _ = unsafe { libc::strlen(cstr.a
    
fn main() {
    // CString
    let cstring = CString::new("foo").expect("CString::new failed");
    let _ = unsafe { libc::strlen(cstring.as_ptr()) };

    // CStr
    let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
    let _ = unsafe { libc::strlen(cstr.as_ptr()) };

    let _ = unsafe { strlen(cstr.as_ptr()) };

    let pcstr: *const &CStr = &cstr;
    let _ = unsafe { strlen((*pcstr).as_ptr()) };

    unsafe fn unsafe_identity<T>(x: T) -> T {
        x
    }
    let _ = unsafe { strlen(unsafe_identity(cstr).as_ptr()) };
    let _ = unsafe { strlen(unsafe { unsafe_identity(cstr) }.as_ptr()) };

    let f: unsafe fn(_) -> _ = unsafe_identity;
    let _ = unsafe { strlen(f(cstr).as_ptr()) };
}