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: mod.rs
    path of file: ./repos/Theseus/tlibc/src/stdio
    
    the code of the file until where you have to start completion: //! 

pub mod printf;
use crate::io::{StringWriter, UnsafeStringWriter};

use core::ffi::VaList;
use alloc::vec::Vec;
use libc::{c_char, c_int, size_t};


// #[no_mangle]
// pub unsafe extern "C" fn vfpri
    
// pub unsafe extern "C" fn vfprintf(file: *mut FILE, format: *const c_char, ap: VaList) -> c_int {
//     let mut file = (*file).lock();
//     if let Err(_) = file.try_set_byte_orientation_unlocked() {
//         return -1;
//     }

//     printf::printf(&mut *file, format, ap)
// }