Guile REPL in Rust

repl.rs

use std::ffi::CString;
use std::env;
use std::ptr;
use libc::{c_char, c_void, c_int};

#[link(name="guile-2.0")]
extern {
    fn scm_shell(argc: c_int, argv: *const *const c_char) -> c_void;
    fn scm_boot_guile(argc: c_int,
                      argv: *const *const c_char,
                      main_func: extern fn(data: *mut c_void, argc: c_int, argv: *const *const c_char) -> c_void,
                      data: *mut c_void);
}

extern "C" fn inner_main(_: *mut c_void, argc: c_int, argv: *const *const c_char) -> c_void {
    unsafe {
        scm_shell(argc, argv)
    }
}

pub fn start_repl() {
    let argv: Vec<CString> = env::args().into_iter().map(|arg| { CString::new(arg).unwrap() } ).collect();
    let args: Vec<*const c_char> = argv.into_iter().map(|arg| { arg.as_ptr() } ).collect();
    unsafe {
        scm_boot_guile(args.len() as c_int, args.as_ptr() as *const *const c_char, inner_main, ptr::null_mut())
    }
}