foo.c

int pants() {
  char *foo = crud();
  printf("Crud: %s\n", foo);
  rust_free(foo);

}

foo.rs

#[no_mangle]
pub extern fn crud() -> *const u8 {
  Box::new("Hello!\0").as_ptr()
}


#[no_mangle]
pub extern fn rust_free(mem : *mut u8) {
  unsafe {
    drop(Box::from_raw(mem));
  }
}