test.rs

extern crate libc;

use std::os::raw::c_char;
use std::mem;
use std::slice;

pub struct CStr {
    inner: [c_char]
}

impl CStr {
    #[inline(never)]
    pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
        let len = libc::strlen(ptr);
        mem::transmute(slice::from_raw_parts(ptr, len as usize + 1))
    }
}

#[inline(never)]
pub fn hello() -> *const u8 {
    unsafe {
        let f = CStr::from_ptr(0xdeadbeefusize as *const _);
        let v: (*const u8, usize) = mem::transmute(f);
        v.0
    }
}

pub fn main() {
    println!("{:?}", hello());
}