src/test/ui/type-sizes.rs

   1 // run-pass
   2
   3 #![allow(non_camel_case_types)]
   4 #![allow(dead_code)]
   5 #![feature(never_type)]
   6
   7 use std::mem::size_of;
   8 use std::num::NonZeroU8;
   9
  10 struct t {a: u8, b: i8}
  11 struct u {a: u8, b: i8, c: u8}
  12 struct v {a: u8, b: i8, c: v2, d: u32}
  13 struct v2 {u: char, v: u8}
  14 struct w {a: isize, b: ()}
  15 struct x {a: isize, b: (), c: ()}
  16 struct y {x: isize}
  17
  18 enum e1 {
  19     a(u8, u32), b(u32), c
  20 }
  21 enum e2 {
  22     a(u32), b
  23 }
  24
  25 #[repr(C, u8)]
  26 enum e3 {
  27     a([u16; 0], u8), b
  28 }
  29
  30 struct ReorderedStruct {
  31     a: u8,
  32     b: u16,
  33     c: u8
  34 }
  35
  36 enum ReorderedEnum {
  37     A(u8, u16, u8),
  38     B(u8, u16, u8),
  39 }
  40
  41 enum ReorderedEnum2 {
  42     A(u8, u32, u8),
  43     B(u16, u8, u16, u8),
  44
  45     // 0x100 niche variants.
  46     _00, _01, _02, _03, _04, _05, _06, _07, _08, _09, _0A, _0B, _0C, _0D, _0E, _0F,
  47     _10, _11, _12, _13, _14, _15, _16, _17, _18, _19, _1A, _1B, _1C, _1D, _1E, _1F,
  48     _20, _21, _22, _23, _24, _25, _26, _27, _28, _29, _2A, _2B, _2C, _2D, _2E, _2F,
  49     _30, _31, _32, _33, _34, _35, _36, _37, _38, _39, _3A, _3B, _3C, _3D, _3E, _3F,
  50     _40, _41, _42, _43, _44, _45, _46, _47, _48, _49, _4A, _4B, _4C, _4D, _4E, _4F,
  51     _50, _51, _52, _53, _54, _55, _56, _57, _58, _59, _5A, _5B, _5C, _5D, _5E, _5F,
  52     _60, _61, _62, _63, _64, _65, _66, _67, _68, _69, _6A, _6B, _6C, _6D, _6E, _6F,
  53     _70, _71, _72, _73, _74, _75, _76, _77, _78, _79, _7A, _7B, _7C, _7D, _7E, _7F,
  54     _80, _81, _82, _83, _84, _85, _86, _87, _88, _89, _8A, _8B, _8C, _8D, _8E, _8F,
  55     _90, _91, _92, _93, _94, _95, _96, _97, _98, _99, _9A, _9B, _9C, _9D, _9E, _9F,
  56     _A0, _A1, _A2, _A3, _A4, _A5, _A6, _A7, _A8, _A9, _AA, _AB, _AC, _AD, _AE, _AF,
  57     _B0, _B1, _B2, _B3, _B4, _B5, _B6, _B7, _B8, _B9, _BA, _BB, _BC, _BD, _BE, _BF,
  58     _C0, _C1, _C2, _C3, _C4, _C5, _C6, _C7, _C8, _C9, _CA, _CB, _CC, _CD, _CE, _CF,
  59     _D0, _D1, _D2, _D3, _D4, _D5, _D6, _D7, _D8, _D9, _DA, _DB, _DC, _DD, _DE, _DF,
  60     _E0, _E1, _E2, _E3, _E4, _E5, _E6, _E7, _E8, _E9, _EA, _EB, _EC, _ED, _EE, _EF,
  61     _F0, _F1, _F2, _F3, _F4, _F5, _F6, _F7, _F8, _F9, _FA, _FB, _FC, _FD, _FE, _FF,
  62 }
  63
  64 enum EnumEmpty {}
  65
  66 enum EnumSingle1 {
  67     A,
  68 }
  69
  70 enum EnumSingle2 {
  71     A = 42 as isize,
  72 }
  73
  74 enum EnumSingle3 {
  75     A,
  76     B(!),
  77 }
  78
  79 #[repr(u8)]
  80 enum EnumSingle4 {
  81     A,
  82 }
  83
  84 #[repr(u8)]
  85 enum EnumSingle5 {
  86     A = 42 as u8,
  87 }
  88
  89 enum EnumWithMaybeUninhabitedVariant<T> {
  90     A(&'static ()),
  91     B(&'static (), T),
  92     C,
  93 }
  94
  95 enum NicheFilledEnumWithAbsentVariant {
  96     A(&'static ()),
  97     B((), !),
  98     C,
  99 }
 100
 101 enum Option2<A, B> {
 102     Some(A, B),
 103     None
 104 }
 105
 106 // Two layouts are considered for `CanBeNicheFilledButShouldnt`:
 107 //   Niche-filling:
 108 //     { u32 (4 bytes), NonZeroU8 + tag in niche (1 byte), padding (3 bytes) }
 109 //   Tagged:
 110 //     { tag (1 byte), NonZeroU8 (1 byte), padding (2 bytes), u32 (4 bytes) }
 111 // Both are the same size (due to padding),
 112 // but the tagged layout is better as the tag creates a niche with 254 invalid values,
 113 // allowing types like `Option<Option<CanBeNicheFilledButShouldnt>>` to fit into 8 bytes.
 114 pub enum CanBeNicheFilledButShouldnt {
 115     A(NonZeroU8, u32),
 116     B
 117 }
 118 pub enum AlwaysTaggedBecauseItHasNoNiche {
 119     A(u8, u32),
 120     B
 121 }
 122
 123 pub fn main() {
 124     assert_eq!(size_of::<u8>(), 1 as usize);
 125     assert_eq!(size_of::<u32>(), 4 as usize);
 126     assert_eq!(size_of::<char>(), 4 as usize);
 127     assert_eq!(size_of::<i8>(), 1 as usize);
 128     assert_eq!(size_of::<i32>(), 4 as usize);
 129     assert_eq!(size_of::<t>(), 2 as usize);
 130     assert_eq!(size_of::<u>(), 3 as usize);
 131     // Alignment causes padding before the char and the u32.
 132
 133     assert_eq!(size_of::<v>(),
 134                 16 as usize);
 135     assert_eq!(size_of::<isize>(), size_of::<usize>());
 136     assert_eq!(size_of::<w>(), size_of::<isize>());
 137     assert_eq!(size_of::<x>(), size_of::<isize>());
 138     assert_eq!(size_of::<isize>(), size_of::<y>());
 139
 140     // Make sure enum types are the appropriate size, mostly
 141     // around ensuring alignment is handled properly
 142
 143     assert_eq!(size_of::<e1>(), 8 as usize);
 144     assert_eq!(size_of::<e2>(), 8 as usize);
 145     assert_eq!(size_of::<e3>(), 4 as usize);
 146     assert_eq!(size_of::<ReorderedStruct>(), 4);
 147     assert_eq!(size_of::<ReorderedEnum>(), 6);
 148     assert_eq!(size_of::<ReorderedEnum2>(), 8);
 149
 150
 151     assert_eq!(size_of::<EnumEmpty>(), 0);
 152     assert_eq!(size_of::<EnumSingle1>(), 0);
 153     assert_eq!(size_of::<EnumSingle2>(), 0);
 154     assert_eq!(size_of::<EnumSingle3>(), 0);
 155     assert_eq!(size_of::<EnumSingle4>(), 1);
 156     assert_eq!(size_of::<EnumSingle5>(), 1);
 157
 158     assert_eq!(size_of::<EnumWithMaybeUninhabitedVariant<!>>(),
 159                size_of::<EnumWithMaybeUninhabitedVariant<()>>());
 160     assert_eq!(size_of::<NicheFilledEnumWithAbsentVariant>(), size_of::<&'static ()>());
 161
 162     assert_eq!(size_of::<Option<Option<(bool, &())>>>(), size_of::<(bool, &())>());
 163     assert_eq!(size_of::<Option<Option<(&(), bool)>>>(), size_of::<(bool, &())>());
 164     assert_eq!(size_of::<Option<Option2<bool, &()>>>(), size_of::<(bool, &())>());
 165     assert_eq!(size_of::<Option<Option2<&(), bool>>>(), size_of::<(bool, &())>());
 166
 167     assert_eq!(size_of::<CanBeNicheFilledButShouldnt>(), 8);
 168     assert_eq!(size_of::<Option<CanBeNicheFilledButShouldnt>>(), 8);
 169     assert_eq!(size_of::<Option<Option<CanBeNicheFilledButShouldnt>>>(), 8);
 170     assert_eq!(size_of::<AlwaysTaggedBecauseItHasNoNiche>(), 8);
 171     assert_eq!(size_of::<Option<AlwaysTaggedBecauseItHasNoNiche>>(), 8);
 172     assert_eq!(size_of::<Option<Option<AlwaysTaggedBecauseItHasNoNiche>>>(), 8);
 173 }