> "gcc -Wall" и Rust  не нужен.

#include<stdio.h>
int main(int argc, char** argv) {
     int (*putit)(char*) = (int (*) (char*)) (argc != 0 ? 0 : puts);
     return putit("bar");
}
$ gcc -Wall test.c && ./a.out
Segmentation fault

$ cat test.rs
use std::env;
use std::io::{Write};
fn put(foo:&[u8]) ->() {
    std::io::stdout().write_all(foo).unwrap();
}
pub fn main() {
    let putit = if env::args().len() !=0 {0} else {put};
    putit(b"hello");
}
$ rustc test.rs
error[E0308]: `if` and `else` have incompatible types
 --> tst.rs:7:52
  |
7 |     let putit = if env::args().len() !=0 {0} else {put};
  |                                           -        ^^^ expected integer, found fn item
  |                                           |
  |                                           expected because of this
  |
  = note: expected type `{integer}`
          found fn item `for<'r> fn(&'r [u8]) {put}

как скажешь.