lib.rs

extern crate libc;
use libc::{c_double, c_void};
use std::os::raw::c_char;

#[derive(Debug)]
pub struct Tdlib {
    instance: *mut c_void
}

#[link(name = "tdjson")]
extern {
    fn td_json_client_create() -> *mut c_void;
    fn td_json_client_destroy(client: *mut c_void);
}

impl Tdlib {
    pub fn create() -> Self {
        let client = unsafe { td_json_client_create() };
        Tdlib { instance: client }
    }
}

impl Drop for Tdlib {
    fn drop(&mut self) {
        unsafe {
            println!("dropping client");
            td_json_client_destroy(self.instance);
        }
    }
}

main.rs

extern crate rust_tdlib;

use rust_tdlib::Tdlib;

fn main() {
    println!("Hello, world!");

    {
        let client = Tdlib::create();
        println!("client: {:?}", client);
        //XXX drops!
    }
    println!("ok")
}

testing.txt

# Now there's some tdlib debug output

13:24:45 qalex@qxps:~/projects/rust/rust-tdlib git [master*]
% cargo run  
    Finished dev [unoptimized + debuginfo] target(s) in 0.00s                                                                                                                                                                                  
     Running `target/debug/rust-tdlib`
Hello, world!
client: Tdlib { instance: 0x7f951b840000 }
dropping client
[ 3][t 4][1535106288.587110758][Td.cpp:4633][!Td][&td_requests] Sending update: updateAuthorizationState {
  authorization_state = authorizationStateWaitTdlibParameters {
  }
}

[ 2][t 4][1535106288.587305546][Td.cpp:4215][!Td]       ON_CLOSED
[ 3][t 4][1535106288.587322950][Td.cpp:4633][!Td][&td_requests] Sending update: updateAuthorizationState {
  authorization_state = authorizationStateClosed {
  }
}

ok