Mirrors/servo
1
0
Fork 0
mirror of https://github.com/servo/servo.git synced 2025-08-07 06:25:32 +01:00
Code Issues Projects Releases Packages Wiki Activity

Use pointer casts instead of tramsutes to raw::TraitObject

Browse source 
Casting `*const T` to `*const U` with `U: Sized` is allowed even if `T: ?Sized`.
This safely extracts the data pointer out of a trait object,
without relying on the memory representation of trait objects.
This commit is contained in:
Simon Sapin 2017-10-13 21:55:11 +02:00
parent 78aaa85aec
commit e7c53d4ca2
3 changed files with 10 additions and 52 deletions
Download patch file Download diff file Expand all files Collapse all files

29
tests/unit/layout/lib.rs
View file

@ -2,36 +2,7 @@
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#![feature(raw)]
extern crate layout;
#[macro_use] extern crate size_of_test;
#[cfg(all(test, target_pointer_width = "64"))] mod size_of;
use std::mem;
use std::ptr;
use std::raw;
#[test]
fn test_trait_object_layout() {
assert_eq!(mem::size_of::<raw::TraitObject>(), mem::size_of::<layout::TraitObject>());
let null: *mut () = ptr::null_mut();
let a = raw::TraitObject {
data: null,
vtable: null,
};
let b = layout::TraitObject {
data: null,
vtable: null,
};
fn offset<T, U>(struct_: &T, field: &U) -> usize {
let addr_struct = struct_ as *const T as usize;
let addr_field = field as *const U as usize;
addr_field - addr_struct
}
assert_eq!(offset(&a, &a.data), offset(&b, &b.data));
assert_eq!(offset(&a, &a.vtable), offset(&b, &b.vtable));
}