src/test/run-pass/fat-ptr-cast.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 #![feature(core)]
  12
  13 use std::mem;
  14 use std::raw;
  15
  16 trait Foo {
  17     fn foo(&self) {}
  18 }
  19
  20 struct Bar;
  21
  22 impl Foo for Bar {}
  23
  24 fn main() {
  25     // Test we can turn a fat pointer to array back into a thin pointer.
  26     let a: *const [i32] = &[1, 2, 3];
  27     let b = a as *const [i32; 2];
  28     unsafe {
  29         assert!(*b == [1, 2]);
  30     }
  31
  32     // Test conversion to an address (usize).
  33     let a: *const [i32; 3] = &[1, 2, 3];
  34     let b: *const [i32] = a;
  35     assert!(a as usize == b as usize);
  36
  37     // And conversion to a void pointer/address for trait objects too.
  38     let a: *mut Foo = &mut Bar;
  39     let b = a as *mut ();
  40     let c = a as usize;
  41
  42     let d = unsafe {
  43         let r: raw::TraitObject = mem::transmute(a);
  44         r.data
  45     };
  46
  47     assert!(b == d);
  48     assert!(c == d as usize);
  49 }