1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
// run-pass
// Test structs with always-unsized fields.
#![allow(warnings)]
#![feature(unsize, ptr_metadata)]
use std::mem;
use std::ptr;
use std::slice;
struct Foo<T> {
f: [T],
}
struct Bar {
f1: usize,
f2: [usize],
}
struct Baz {
f1: usize,
f2: str,
}
trait Tr {
fn foo(&self) -> usize;
}
struct St {
f: usize,
}
impl Tr for St {
fn foo(&self) -> usize {
self.f
}
}
struct Qux<'a> {
f: Tr + 'a,
}
pub fn main() {
let _: &Foo<f64>;
let _: &Bar;
let _: &Baz;
let _: Box<Foo<i32>>;
let _: Box<Bar>;
let _: Box<Baz>;
let _ = mem::size_of::<Box<Foo<u8>>>();
let _ = mem::size_of::<Box<Bar>>();
let _ = mem::size_of::<Box<Baz>>();
unsafe {
struct Foo_<T> {
f: [T; 3],
}
let data: Box<Foo_<i32>> = Box::new(Foo_ { f: [1, 2, 3] });
let x: &Foo<i32> = mem::transmute(ptr::slice_from_raw_parts(&*data, 3));
assert_eq!(x.f.len(), 3);
assert_eq!(x.f[0], 1);
struct Baz_ {
f1: usize,
f2: [u8; 5],
}
let data: Box<_> =
Box::new(Baz_ { f1: 42, f2: ['a' as u8, 'b' as u8, 'c' as u8, 'd' as u8, 'e' as u8] });
let x: &Baz = mem::transmute(ptr::slice_from_raw_parts(&*data, 5));
assert_eq!(x.f1, 42);
let chs: Vec<char> = x.f2.chars().collect();
assert_eq!(chs.len(), 5);
assert_eq!(chs[0], 'a');
assert_eq!(chs[1], 'b');
assert_eq!(chs[2], 'c');
assert_eq!(chs[3], 'd');
assert_eq!(chs[4], 'e');
struct Qux_ {
f: St,
}
let obj: Box<St> = Box::new(St { f: 42 });
let obj: &Tr = &*obj;
let data: Box<_> = Box::new(Qux_ { f: St { f: 234 } });
let x: &Qux = &*ptr::from_raw_parts::<Qux>((&*data as *const _).cast(), ptr::metadata(obj));
assert_eq!(x.f.foo(), 234);
}
}
|
