File: enum-layout-optimization.rs

package info (click to toggle)
rustc-web 1.78.0%2Bdfsg1-2~deb12u3
  • links: PTS, VCS
  • area: main
  • in suites: bookworm
  • size: 1,245,420 kB
  • sloc: xml: 147,985; javascript: 18,022; sh: 11,083; python: 10,265; ansic: 6,172; cpp: 5,023; asm: 4,390; makefile: 4,269
file content (50 lines) | stat: -rw-r--r-- 1,205 bytes parent folder | download | duplicates (6)
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
//@ run-pass
// Test that we will do various size optimizations to enum layout, but
// *not* if `#[repr(u8)]` or `#[repr(C)]` is passed. See also #40029.

#![allow(dead_code)]

use std::mem;

enum Nullable<T> {
    Alive(T),
    Dropped,
}

#[repr(u8)]
enum NullableU8<T> {
    Alive(T),
    Dropped,
}

#[repr(C)]
enum NullableC<T> {
    Alive(T),
    Dropped,
}

struct StructNewtype<T>(T);

#[repr(C)]
struct StructNewtypeC<T>(T);

enum EnumNewtype<T> { Variant(T) }

#[repr(u8)]
enum EnumNewtypeU8<T> { Variant(T) }

#[repr(C)]
enum EnumNewtypeC<T> { Variant(T) }

fn main() {
    assert!(mem::size_of::<Box<i32>>() == mem::size_of::<Nullable<Box<i32>>>());
    assert!(mem::size_of::<Box<i32>>() < mem::size_of::<NullableU8<Box<i32>>>());
    assert!(mem::size_of::<Box<i32>>() < mem::size_of::<NullableC<Box<i32>>>());

    assert!(mem::size_of::<i32>() == mem::size_of::<StructNewtype<i32>>());
    assert!(mem::size_of::<i32>() == mem::size_of::<StructNewtypeC<i32>>());

    assert!(mem::size_of::<i32>() == mem::size_of::<EnumNewtype<i32>>());
    assert!(mem::size_of::<i32>() < mem::size_of::<EnumNewtypeU8<i32>>());
    assert!(mem::size_of::<i32>() < mem::size_of::<EnumNewtypeC<i32>>());
}