rust/example/mini_core_hello_world.rs

// Adapted from https://github.com/sunfishcode/mir2cranelift/blob/master/rust-examples/nocore-hello-world.rs

#![feature(no_core, unboxed_closures, start, lang_items, box_syntax, slice_patterns, never_type, linkage)]
#![no_core]
#![allow(dead_code)]

extern crate mini_core;

use mini_core::*;
use mini_core::libc::*;

unsafe extern "C" fn my_puts(s: *const u8) {
    puts(s);
}

#[lang = "termination"]
trait Termination {
    fn report(self) -> i32;
}

impl Termination for () {
    fn report(self) -> i32 {
        unsafe {
            NUM = 6 * 7 + 1 + (1u8 == 1u8) as u8; // 44
            *NUM_REF as i32
        }
    }
}

trait SomeTrait {
    fn object_safe(&self);
}

impl SomeTrait for &'static str {
    fn object_safe(&self) {
        unsafe {
            puts(*self as *const str as *const u8);
        }
    }
}

struct NoisyDrop {
    text: &'static str,
    inner: NoisyDropInner,
}

struct NoisyDropInner;

impl Drop for NoisyDrop {
    fn drop(&mut self) {
        unsafe {
            puts(self.text as *const str as *const u8);
        }
    }
}

impl Drop for NoisyDropInner {
    fn drop(&mut self) {
        unsafe {
            puts("Inner got dropped!\0" as *const str as *const u8);
        }
    }
}

impl SomeTrait for NoisyDrop {
    fn object_safe(&self) {}
}

enum Ordering {
    Less = -1,
    Equal = 0,
    Greater = 1,
}

#[lang = "start"]
fn start<T: Termination + 'static>(
    main: fn() -> T,
    argc: isize,
    argv: *const *const u8,
) -> isize {
    if argc == 3 {
        unsafe { puts(*argv); }
        unsafe { puts(*((argv as usize + intrinsics::size_of::<*const u8>()) as *const *const u8)); }
        unsafe { puts(*((argv as usize + 2 * intrinsics::size_of::<*const u8>()) as *const *const u8)); }
    }

    main().report();
    0
}

static mut NUM: u8 = 6 * 7;
static NUM_REF: &'static u8 = unsafe { &NUM };

macro_rules! assert {
    ($e:expr) => {
        if !$e {
            panic(&(stringify!(! $e), file!(), line!(), 0));
        }
    };
}

macro_rules! assert_eq {
    ($l:expr, $r: expr) => {
        if $l != $r {
            panic(&(stringify!($l != $r), file!(), line!(), 0));
        }
    }
}

struct Unique<T: ?Sized> {
    pointer: *const T,
    _marker: PhantomData<T>,
}

impl<T: ?Sized, U: ?Sized> CoerceUnsized<Unique<U>> for Unique<T> where T: Unsize<U> {}

fn take_f32(_f: f32) {}
fn take_unique(_u: Unique<()>) {}

fn return_u128_pair() -> (u128, u128) {
    (0, 0)
}

fn call_return_u128_pair() {
    return_u128_pair();
}

fn main() {
    take_unique(Unique {
        pointer: 0 as *const (),
        _marker: PhantomData,
    });
    take_f32(0.1);

    call_return_u128_pair();

    let slice = &[0, 1] as &[i32];
    let slice_ptr = slice as *const [i32] as *const i32;

    // FIXME On macOS statics and promoted constants have the wrong alignment. This causes this
    // assertion to fail.
    if cfg!(not(target_os = "macos")) {
        assert_eq!(slice_ptr as usize % 4, 0);
    }

    //return;

    unsafe {
        printf("Hello %s\n\0" as *const str as *const i8, "printf\0" as *const str as *const i8);

        let hello: &[u8] = b"Hello\0" as &[u8; 6];
        let ptr: *const u8 = hello as *const [u8] as *const u8;
        puts(ptr);

        let world: Box<&str> = box "World!\0";
        puts(*world as *const str as *const u8);
        world as Box<dyn SomeTrait>;

        assert_eq!(intrinsics::bitreverse(0b10101000u8), 0b00010101u8);

        assert_eq!(intrinsics::bswap(0xabu8), 0xabu8);
        assert_eq!(intrinsics::bswap(0xddccu16), 0xccddu16);
        assert_eq!(intrinsics::bswap(0xffee_ddccu32), 0xccdd_eeffu32);
        assert_eq!(intrinsics::bswap(0x1234_5678_ffee_ddccu64), 0xccdd_eeff_7856_3412u64);

        assert_eq!(intrinsics::size_of_val(hello) as u8, 6);

        let chars = &['C', 'h', 'a', 'r', 's'];
        let chars = chars as &[char];
        assert_eq!(intrinsics::size_of_val(chars) as u8, 4 * 5);

        let a: &dyn SomeTrait = &"abc\0";
        a.object_safe();

        assert_eq!(intrinsics::size_of_val(a) as u8, 16);
        assert_eq!(intrinsics::size_of_val(&0u32) as u8, 4);

        assert_eq!(intrinsics::min_align_of::<u16>() as u8, 2);
        assert_eq!(intrinsics::min_align_of_val(&a) as u8, intrinsics::min_align_of::<&str>() as u8);

        assert!(!intrinsics::needs_drop::<u8>());
        assert!(intrinsics::needs_drop::<NoisyDrop>());

        Unique {
            pointer: 0 as *const &str,
            _marker: PhantomData,
        } as Unique<dyn SomeTrait>;

        struct MyDst<T: ?Sized>(T);

        intrinsics::size_of_val(&MyDst([0u8; 4]) as &MyDst<[u8]>);

        struct Foo {
            x: u8,
            y: !,
        }

        unsafe fn zeroed<T>() -> T {
            intrinsics::init::<T>()
        }

        unsafe fn uninitialized<T>() -> T {
            MaybeUninit { uninit: () }.value
        }

        zeroed::<(u8, u8)>();
        #[allow(unreachable_code)]
        {
            if false {
                zeroed::<!>();
                zeroed::<Foo>();
                uninitialized::<Foo>();
            }
        }
    }

    let _ = box NoisyDrop {
        text: "Boxed outer got dropped!\0",
        inner: NoisyDropInner,
    } as Box<dyn SomeTrait>;

    const FUNC_REF: Option<fn()> = Some(main);
    match FUNC_REF {
        Some(_) => {},
        None => assert!(false),
    }

    match Ordering::Less {
        Ordering::Less => {},
        _ => assert!(false),
    }

    [NoisyDropInner, NoisyDropInner];

    let x = &[0u32, 42u32] as &[u32];
    match x {
        [] => assert_eq!(0u32, 1),
        [_, ref y @ ..] => assert_eq!(&x[1] as *const u32 as usize, &y[0] as *const u32 as usize),
    }

    assert_eq!(((|()| 42u8) as fn(()) -> u8)(()), 42);

    extern {
        #[linkage = "weak"]
        static ABC: *const u8;
    }

    {
        extern {
            #[linkage = "weak"]
            static ABC: *const u8;
        }
    }

    unsafe { assert_eq!(ABC as usize, 0); }

    &mut (|| Some(0 as *const ())) as &mut dyn FnMut() -> Option<*const ()>;

    let f = 1000.0;
    assert_eq!(f as u8, 255);
    let f2 = -1000.0;
    assert_eq!(f2 as i8, -128);
    assert_eq!(f2 as u8, 0);

    static ANOTHER_STATIC: &u8 = &A_STATIC;
    assert_eq!(*ANOTHER_STATIC, 42);

    check_niche_behavior();
}

// Copied ui/issues/issue-61696.rs

pub enum Infallible {}

// The check that the `bool` field of `V1` is encoding a "niche variant"
// (i.e. not `V1`, so `V3` or `V4`) used to be mathematically incorrect,
// causing valid `V1` values to be interpreted as other variants.
pub enum E1 {
    V1 { f: bool },
    V2 { f: Infallible },
    V3,
    V4,
}

// Computing the discriminant used to be done using the niche type (here `u8`,
// from the `bool` field of `V1`), overflowing for variants with large enough
// indices (`V3` and `V4`), causing them to be interpreted as other variants.
pub enum E2<X> {
    V1 { f: bool },

    /*_00*/ _01(X), _02(X), _03(X), _04(X), _05(X), _06(X), _07(X),
    _08(X), _09(X), _0A(X), _0B(X), _0C(X), _0D(X), _0E(X), _0F(X),
    _10(X), _11(X), _12(X), _13(X), _14(X), _15(X), _16(X), _17(X),
    _18(X), _19(X), _1A(X), _1B(X), _1C(X), _1D(X), _1E(X), _1F(X),
    _20(X), _21(X), _22(X), _23(X), _24(X), _25(X), _26(X), _27(X),
    _28(X), _29(X), _2A(X), _2B(X), _2C(X), _2D(X), _2E(X), _2F(X),
    _30(X), _31(X), _32(X), _33(X), _34(X), _35(X), _36(X), _37(X),
    _38(X), _39(X), _3A(X), _3B(X), _3C(X), _3D(X), _3E(X), _3F(X),
    _40(X), _41(X), _42(X), _43(X), _44(X), _45(X), _46(X), _47(X),
    _48(X), _49(X), _4A(X), _4B(X), _4C(X), _4D(X), _4E(X), _4F(X),
    _50(X), _51(X), _52(X), _53(X), _54(X), _55(X), _56(X), _57(X),
    _58(X), _59(X), _5A(X), _5B(X), _5C(X), _5D(X), _5E(X), _5F(X),
    _60(X), _61(X), _62(X), _63(X), _64(X), _65(X), _66(X), _67(X),
    _68(X), _69(X), _6A(X), _6B(X), _6C(X), _6D(X), _6E(X), _6F(X),
    _70(X), _71(X), _72(X), _73(X), _74(X), _75(X), _76(X), _77(X),
    _78(X), _79(X), _7A(X), _7B(X), _7C(X), _7D(X), _7E(X), _7F(X),
    _80(X), _81(X), _82(X), _83(X), _84(X), _85(X), _86(X), _87(X),
    _88(X), _89(X), _8A(X), _8B(X), _8C(X), _8D(X), _8E(X), _8F(X),
    _90(X), _91(X), _92(X), _93(X), _94(X), _95(X), _96(X), _97(X),
    _98(X), _99(X), _9A(X), _9B(X), _9C(X), _9D(X), _9E(X), _9F(X),
    _A0(X), _A1(X), _A2(X), _A3(X), _A4(X), _A5(X), _A6(X), _A7(X),
    _A8(X), _A9(X), _AA(X), _AB(X), _AC(X), _AD(X), _AE(X), _AF(X),
    _B0(X), _B1(X), _B2(X), _B3(X), _B4(X), _B5(X), _B6(X), _B7(X),
    _B8(X), _B9(X), _BA(X), _BB(X), _BC(X), _BD(X), _BE(X), _BF(X),
    _C0(X), _C1(X), _C2(X), _C3(X), _C4(X), _C5(X), _C6(X), _C7(X),
    _C8(X), _C9(X), _CA(X), _CB(X), _CC(X), _CD(X), _CE(X), _CF(X),
    _D0(X), _D1(X), _D2(X), _D3(X), _D4(X), _D5(X), _D6(X), _D7(X),
    _D8(X), _D9(X), _DA(X), _DB(X), _DC(X), _DD(X), _DE(X), _DF(X),
    _E0(X), _E1(X), _E2(X), _E3(X), _E4(X), _E5(X), _E6(X), _E7(X),
    _E8(X), _E9(X), _EA(X), _EB(X), _EC(X), _ED(X), _EE(X), _EF(X),
    _F0(X), _F1(X), _F2(X), _F3(X), _F4(X), _F5(X), _F6(X), _F7(X),
    _F8(X), _F9(X), _FA(X), _FB(X), _FC(X), _FD(X), _FE(X), _FF(X),

    V3,
    V4,
}

fn check_niche_behavior () {
    if let E1::V2 { .. } = (E1::V1 { f: true }) {
        unsafe { intrinsics::abort(); }
    }

    if let E2::V1 { .. } = E2::V3::<Infallible> {
        unsafe { intrinsics::abort(); }
    }
}