lib.rs

#![feature(libc)]
extern crate libc;

use libc::*;
use std::ffi::{CStr, CString};

#[repr(C)]
pub struct SampleStruct {
   i: i32,
   b: bool,
   s: *const c_char
}

#[no_mangle]
pub extern fn create_sample_struct() -> *mut SampleStruct {
    let b = Box::new(SampleStruct {
        i: 1,
        b: true,
        s: CString::new("hello").unwrap().into_raw()
    });

    Box::into_raw(b)
}

#[no_mangle]
pub extern fn free_sample_struct(s: *mut SampleStruct) {
    unsafe {
        drop(Box::from_raw(s));
    }
}