sync.rs

use alloc::sync::*;
use std::alloc::{AllocError, Allocator, Layout};
use std::any::Any;
use std::clone::Clone;
use std::mem::MaybeUninit;
use std::option::Option::None;
use std::ptr::NonNull;
use std::sync::Mutex;
use std::sync::atomic::Ordering::*;
use std::sync::atomic::{self, AtomicUsize};
use std::sync::mpsc::channel;
use std::thread;

struct Canary(*mut AtomicUsize);

impl Drop for Canary {
    fn drop(&mut self) {
        unsafe {
            match *self {
                Canary(c) => {
                    (*c).fetch_add(1, SeqCst);
                }
            }
        }
    }
}

struct AllocCanary<'a>(&'a AtomicUsize);

impl<'a> AllocCanary<'a> {
    fn new(counter: &'a AtomicUsize) -> Self {
        counter.fetch_add(1, SeqCst);
        Self(counter)
    }
}

unsafe impl Allocator for AllocCanary<'_> {
    fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
        std::alloc::Global.allocate(layout)
    }

    unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
        unsafe { std::alloc::Global.deallocate(ptr, layout) }
    }
}

impl Clone for AllocCanary<'_> {
    fn clone(&self) -> Self {
        Self::new(self.0)
    }
}

impl Drop for AllocCanary<'_> {
    fn drop(&mut self) {
        self.0.fetch_sub(1, SeqCst);
    }
}

#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn manually_share_arc() {
    let v = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
    let arc_v = Arc::new(v);

    let (tx, rx) = channel();

    let _t = thread::spawn(move || {
        let arc_v: Arc<Vec<i32>> = rx.recv().unwrap();
        assert_eq!((*arc_v)[3], 4);
    });

    tx.send(arc_v.clone()).unwrap();

    assert_eq!((*arc_v)[2], 3);
    assert_eq!((*arc_v)[4], 5);
}

#[test]
fn test_arc_get_mut() {
    let mut x = Arc::new(3);
    *Arc::get_mut(&mut x).unwrap() = 4;
    assert_eq!(*x, 4);
    let y = x.clone();
    assert!(Arc::get_mut(&mut x).is_none());
    drop(y);
    assert!(Arc::get_mut(&mut x).is_some());
    let _w = Arc::downgrade(&x);
    assert!(Arc::get_mut(&mut x).is_none());
}

#[test]
fn weak_counts() {
    assert_eq!(Weak::weak_count(&Weak::<u64>::new()), 0);
    assert_eq!(Weak::strong_count(&Weak::<u64>::new()), 0);

    let a = Arc::new(0);
    let w = Arc::downgrade(&a);
    assert_eq!(Weak::strong_count(&w), 1);
    assert_eq!(Weak::weak_count(&w), 1);
    let w2 = w.clone();
    assert_eq!(Weak::strong_count(&w), 1);
    assert_eq!(Weak::weak_count(&w), 2);
    assert_eq!(Weak::strong_count(&w2), 1);
    assert_eq!(Weak::weak_count(&w2), 2);
    drop(w);
    assert_eq!(Weak::strong_count(&w2), 1);
    assert_eq!(Weak::weak_count(&w2), 1);
    let a2 = a.clone();
    assert_eq!(Weak::strong_count(&w2), 2);
    assert_eq!(Weak::weak_count(&w2), 1);
    drop(a2);
    drop(a);
    assert_eq!(Weak::strong_count(&w2), 0);
    assert_eq!(Weak::weak_count(&w2), 0);
    drop(w2);
}

#[test]
fn try_unwrap() {
    let x = Arc::new(3);
    assert_eq!(Arc::try_unwrap(x), Ok(3));
    let x = Arc::new(4);
    let _y = x.clone();
    assert_eq!(Arc::try_unwrap(x), Err(Arc::new(4)));
    let x = Arc::new(5);
    let _w = Arc::downgrade(&x);
    assert_eq!(Arc::try_unwrap(x), Ok(5));
}

#[test]
#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
fn into_inner() {
    for _ in 0..100
    // ^ Increase chances of hitting potential race conditions
    {
        let x = Arc::new(3);
        let y = Arc::clone(&x);
        let r_thread = std::thread::spawn(|| Arc::into_inner(x));
        let s_thread = std::thread::spawn(|| Arc::into_inner(y));
        let r = r_thread.join().expect("r_thread panicked");
        let s = s_thread.join().expect("s_thread panicked");
        assert!(
            matches!((r, s), (None, Some(3)) | (Some(3), None)),
            "assertion failed: unexpected result `{:?}`\
            \n  expected `(None, Some(3))` or `(Some(3), None)`",
            (r, s),
        );
    }

    let x = Arc::new(3);
    assert_eq!(Arc::into_inner(x), Some(3));

    let x = Arc::new(4);
    let y = Arc::clone(&x);
    assert_eq!(Arc::into_inner(x), None);
    assert_eq!(Arc::into_inner(y), Some(4));

    let x = Arc::new(5);
    let _w = Arc::downgrade(&x);
    assert_eq!(Arc::into_inner(x), Some(5));
}

#[test]
fn into_from_raw() {
    let x = Arc::new(Box::new("hello"));
    let y = x.clone();

    let x_ptr = Arc::into_raw(x);
    drop(y);
    unsafe {
        assert_eq!(**x_ptr, "hello");

        let x = Arc::from_raw(x_ptr);
        assert_eq!(**x, "hello");

        assert_eq!(Arc::try_unwrap(x).map(|x| *x), Ok("hello"));
    }
}

#[test]
fn test_into_from_raw_unsized() {
    use std::fmt::Display;
    use std::string::ToString;

    let arc: Arc<str> = Arc::from("foo");

    let ptr = Arc::into_raw(arc.clone());
    let arc2 = unsafe { Arc::from_raw(ptr) };

    assert_eq!(unsafe { &*ptr }, "foo");
    assert_eq!(arc, arc2);

    let arc: Arc<dyn Display> = Arc::new(123);

    let ptr = Arc::into_raw(arc.clone());
    let arc2 = unsafe { Arc::from_raw(ptr) };

    assert_eq!(unsafe { &*ptr }.to_string(), "123");
    assert_eq!(arc2.to_string(), "123");
}

#[test]
fn into_from_weak_raw() {
    let x = Arc::new(Box::new("hello"));
    let y = Arc::downgrade(&x);

    let y_ptr = Weak::into_raw(y);
    unsafe {
        assert_eq!(**y_ptr, "hello");

        let y = Weak::from_raw(y_ptr);
        let y_up = Weak::upgrade(&y).unwrap();
        assert_eq!(**y_up, "hello");
        drop(y_up);

        assert_eq!(Arc::try_unwrap(x).map(|x| *x), Ok("hello"));
    }
}

#[test]
fn test_into_from_weak_raw_unsized() {
    use std::fmt::Display;
    use std::string::ToString;

    let arc: Arc<str> = Arc::from("foo");
    let weak: Weak<str> = Arc::downgrade(&arc);

    let ptr = Weak::into_raw(weak.clone());
    let weak2 = unsafe { Weak::from_raw(ptr) };

    assert_eq!(unsafe { &*ptr }, "foo");
    assert!(weak.ptr_eq(&weak2));

    let arc: Arc<dyn Display> = Arc::new(123);
    let weak: Weak<dyn Display> = Arc::downgrade(&arc);

    let ptr = Weak::into_raw(weak.clone());
    let weak2 = unsafe { Weak::from_raw(ptr) };

    assert_eq!(unsafe { &*ptr }.to_string(), "123");
    assert!(weak.ptr_eq(&weak2));
}

#[test]
fn test_cowarc_clone_make_mut() {
    let mut cow0 = Arc::new(75);
    let mut cow1 = cow0.clone();
    let mut cow2 = cow1.clone();

    assert!(75 == *Arc::make_mut(&mut cow0));
    assert!(75 == *Arc::make_mut(&mut cow1));
    assert!(75 == *Arc::make_mut(&mut cow2));

    *Arc::make_mut(&mut cow0) += 1;
    *Arc::make_mut(&mut cow1) += 2;
    *Arc::make_mut(&mut cow2) += 3;

    assert!(76 == *cow0);
    assert!(77 == *cow1);
    assert!(78 == *cow2);

    // none should point to the same backing memory
    assert!(*cow0 != *cow1);
    assert!(*cow0 != *cow2);
    assert!(*cow1 != *cow2);
}

#[test]
fn test_cowarc_clone_unique2() {
    let mut cow0 = Arc::new(75);
    let cow1 = cow0.clone();
    let cow2 = cow1.clone();

    assert!(75 == *cow0);
    assert!(75 == *cow1);
    assert!(75 == *cow2);

    *Arc::make_mut(&mut cow0) += 1;
    assert!(76 == *cow0);
    assert!(75 == *cow1);
    assert!(75 == *cow2);

    // cow1 and cow2 should share the same contents
    // cow0 should have a unique reference
    assert!(*cow0 != *cow1);
    assert!(*cow0 != *cow2);
    assert!(*cow1 == *cow2);
}

#[test]
fn test_cowarc_clone_weak() {
    let mut cow0 = Arc::new(75);
    let cow1_weak = Arc::downgrade(&cow0);

    assert!(75 == *cow0);
    assert!(75 == *cow1_weak.upgrade().unwrap());

    *Arc::make_mut(&mut cow0) += 1;

    assert!(76 == *cow0);
    assert!(cow1_weak.upgrade().is_none());
}

#[test]
fn test_live() {
    let x = Arc::new(5);
    let y = Arc::downgrade(&x);
    assert!(y.upgrade().is_some());
}

#[test]
fn test_dead() {
    let x = Arc::new(5);
    let y = Arc::downgrade(&x);
    drop(x);
    assert!(y.upgrade().is_none());
}

#[test]
fn weak_self_cyclic() {
    struct Cycle {
        x: Mutex<Option<Weak<Cycle>>>,
    }

    let a = Arc::new(Cycle { x: Mutex::new(None) });
    let b = Arc::downgrade(&a.clone());
    *a.x.lock().unwrap() = Some(b);

    // hopefully we don't double-free (or leak)...
}

#[test]
fn drop_arc() {
    let mut canary = AtomicUsize::new(0);
    let x = Arc::new(Canary(&mut canary as *mut AtomicUsize));
    drop(x);
    assert!(canary.load(Acquire) == 1);
}

#[test]
fn drop_arc_weak() {
    let mut canary = AtomicUsize::new(0);
    let arc = Arc::new(Canary(&mut canary as *mut AtomicUsize));
    let arc_weak = Arc::downgrade(&arc);
    assert!(canary.load(Acquire) == 0);
    drop(arc);
    assert!(canary.load(Acquire) == 1);
    drop(arc_weak);
}

#[test]
fn test_strong_count() {
    let a = Arc::new(0);
    assert!(Arc::strong_count(&a) == 1);
    let w = Arc::downgrade(&a);
    assert!(Arc::strong_count(&a) == 1);
    let b = w.upgrade().expect("");
    assert!(Arc::strong_count(&b) == 2);
    assert!(Arc::strong_count(&a) == 2);
    drop(w);
    drop(a);
    assert!(Arc::strong_count(&b) == 1);
    let c = b.clone();
    assert!(Arc::strong_count(&b) == 2);
    assert!(Arc::strong_count(&c) == 2);
}

#[test]
fn test_weak_count() {
    let a = Arc::new(0);
    assert!(Arc::strong_count(&a) == 1);
    assert!(Arc::weak_count(&a) == 0);
    let w = Arc::downgrade(&a);
    assert!(Arc::strong_count(&a) == 1);
    assert!(Arc::weak_count(&a) == 1);
    let x = w.clone();
    assert!(Arc::weak_count(&a) == 2);
    drop(w);
    drop(x);
    assert!(Arc::strong_count(&a) == 1);
    assert!(Arc::weak_count(&a) == 0);
    let c = a.clone();
    assert!(Arc::strong_count(&a) == 2);
    assert!(Arc::weak_count(&a) == 0);
    let d = Arc::downgrade(&c);
    assert!(Arc::weak_count(&c) == 1);
    assert!(Arc::strong_count(&c) == 2);

    drop(a);
    drop(c);
    drop(d);
}

#[test]
fn show_arc() {
    let a = Arc::new(5);
    assert_eq!(format!("{a:?}"), "5");
}

// Make sure deriving works with Arc<T>
#[derive(Eq, Ord, PartialEq, PartialOrd, Clone, Debug, Default)]
struct _Foo {
    inner: Arc<i32>,
}

#[test]
fn test_unsized() {
    let x: Arc<[i32]> = Arc::new([1, 2, 3]);
    assert_eq!(format!("{x:?}"), "[1, 2, 3]");
    let y = Arc::downgrade(&x.clone());
    drop(x);
    assert!(y.upgrade().is_none());
}

#[test]
fn test_maybe_thin_unsized() {
    // If/when custom thin DSTs exist, this test should be updated to use one
    use std::ffi::CStr;

    let x: Arc<CStr> = Arc::from(c"swordfish");
    assert_eq!(format!("{x:?}"), "\"swordfish\"");
    let y: Weak<CStr> = Arc::downgrade(&x);
    drop(x);

    // At this point, the weak points to a dropped DST
    assert!(y.upgrade().is_none());
    // But we still need to be able to get the alloc layout to drop.
    // CStr has no drop glue, but custom DSTs might, and need to work.
    drop(y);
}

#[test]
fn test_from_owned() {
    let foo = 123;
    let foo_arc = Arc::from(foo);
    assert!(123 == *foo_arc);
}

#[test]
fn test_new_weak() {
    let foo: Weak<usize> = Weak::new();
    assert!(foo.upgrade().is_none());
}

#[test]
fn test_ptr_eq() {
    let five = Arc::new(5);
    let same_five = five.clone();
    let other_five = Arc::new(5);

    assert!(Arc::ptr_eq(&five, &same_five));
    assert!(!Arc::ptr_eq(&five, &other_five));
}

#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn test_weak_count_locked() {
    let mut a = Arc::new(atomic::AtomicBool::new(false));
    let a2 = a.clone();
    let t = thread::spawn(move || {
        // Miri is too slow
        let count = if cfg!(miri) { 1000 } else { 1000000 };
        for _i in 0..count {
            Arc::get_mut(&mut a);
        }
        a.store(true, SeqCst);
    });

    while !a2.load(SeqCst) {
        let n = Arc::weak_count(&a2);
        assert!(n < 2, "bad weak count: {}", n);
        #[cfg(miri)] // Miri's scheduler does not guarantee liveness, and thus needs this hint.
        std::hint::spin_loop();
    }
    t.join().unwrap();
}

#[test]
fn test_from_str() {
    let r: Arc<str> = Arc::from("foo");

    assert_eq!(&r[..], "foo");
}

#[test]
fn test_copy_from_slice() {
    let s: &[u32] = &[1, 2, 3];
    let r: Arc<[u32]> = Arc::from(s);

    assert_eq!(&r[..], [1, 2, 3]);
}

#[test]
fn test_clone_from_slice() {
    #[derive(Clone, Debug, Eq, PartialEq)]
    struct X(u32);

    let s: &[X] = &[X(1), X(2), X(3)];
    let r: Arc<[X]> = Arc::from(s);

    assert_eq!(&r[..], s);
}

#[test]
#[should_panic]
fn test_clone_from_slice_panic() {
    use std::string::{String, ToString};

    struct Fail(u32, String);

    impl Clone for Fail {
        fn clone(&self) -> Fail {
            if self.0 == 2 {
                panic!();
            }
            Fail(self.0, self.1.clone())
        }
    }

    let s: &[Fail] =
        &[Fail(0, "foo".to_string()), Fail(1, "bar".to_string()), Fail(2, "baz".to_string())];

    // Should panic, but not cause memory corruption
    let _r: Arc<[Fail]> = Arc::from(s);
}

#[test]
fn test_from_box() {
    let b: Box<u32> = Box::new(123);
    let r: Arc<u32> = Arc::from(b);

    assert_eq!(*r, 123);
}

#[test]
fn test_from_box_str() {
    use std::string::String;

    let s = String::from("foo").into_boxed_str();
    let r: Arc<str> = Arc::from(s);

    assert_eq!(&r[..], "foo");
}

#[test]
fn test_from_box_slice() {
    let s = vec![1, 2, 3].into_boxed_slice();
    let r: Arc<[u32]> = Arc::from(s);

    assert_eq!(&r[..], [1, 2, 3]);
}

#[test]
fn test_from_box_trait() {
    use std::fmt::Display;
    use std::string::ToString;

    let b: Box<dyn Display> = Box::new(123);
    let r: Arc<dyn Display> = Arc::from(b);

    assert_eq!(r.to_string(), "123");
}

#[test]
fn test_from_box_trait_zero_sized() {
    use std::fmt::Debug;

    let b: Box<dyn Debug> = Box::new(());
    let r: Arc<dyn Debug> = Arc::from(b);

    assert_eq!(format!("{r:?}"), "()");
}

#[test]
fn test_from_vec() {
    let v = vec![1, 2, 3];
    let r: Arc<[u32]> = Arc::from(v);

    assert_eq!(&r[..], [1, 2, 3]);
}

#[test]
fn test_downcast() {
    use std::any::Any;

    let r1: Arc<dyn Any + Send + Sync> = Arc::new(i32::MAX);
    let r2: Arc<dyn Any + Send + Sync> = Arc::new("abc");

    assert!(r1.clone().downcast::<u32>().is_err());

    let r1i32 = r1.downcast::<i32>();
    assert!(r1i32.is_ok());
    assert_eq!(r1i32.unwrap(), Arc::new(i32::MAX));

    assert!(r2.clone().downcast::<i32>().is_err());

    let r2str = r2.downcast::<&'static str>();
    assert!(r2str.is_ok());
    assert_eq!(r2str.unwrap(), Arc::new("abc"));
}

#[test]
fn test_array_from_slice() {
    let v = vec![1, 2, 3];
    let r: Arc<[u32]> = Arc::from(v);

    let a: Result<Arc<[u32; 3]>, _> = r.clone().try_into();
    assert!(a.is_ok());

    let a: Result<Arc<[u32; 2]>, _> = r.clone().try_into();
    assert!(a.is_err());
}

#[test]
fn test_arc_cyclic_with_zero_refs() {
    struct ZeroRefs {
        inner: Weak<ZeroRefs>,
    }
    let zero_refs = Arc::new_cyclic(|inner| {
        assert_eq!(inner.strong_count(), 0);
        assert!(inner.upgrade().is_none());
        ZeroRefs { inner: Weak::new() }
    });

    assert_eq!(Arc::strong_count(&zero_refs), 1);
    assert_eq!(Arc::weak_count(&zero_refs), 0);
    assert_eq!(zero_refs.inner.strong_count(), 0);
    assert_eq!(zero_refs.inner.weak_count(), 0);
}

#[test]
fn test_arc_new_cyclic_one_ref() {
    struct OneRef {
        inner: Weak<OneRef>,
    }
    let one_ref = Arc::new_cyclic(|inner| {
        assert_eq!(inner.strong_count(), 0);
        assert!(inner.upgrade().is_none());
        OneRef { inner: inner.clone() }
    });

    assert_eq!(Arc::strong_count(&one_ref), 1);
    assert_eq!(Arc::weak_count(&one_ref), 1);

    let one_ref2 = Weak::upgrade(&one_ref.inner).unwrap();
    assert!(Arc::ptr_eq(&one_ref, &one_ref2));

    assert_eq!(Arc::strong_count(&one_ref), 2);
    assert_eq!(Arc::weak_count(&one_ref), 1);
}

#[test]
fn test_arc_cyclic_two_refs() {
    struct TwoRefs {
        inner1: Weak<TwoRefs>,
        inner2: Weak<TwoRefs>,
    }
    let two_refs = Arc::new_cyclic(|inner| {
        assert_eq!(inner.strong_count(), 0);
        assert!(inner.upgrade().is_none());

        let inner1 = inner.clone();
        let inner2 = inner1.clone();

        TwoRefs { inner1, inner2 }
    });

    assert_eq!(Arc::strong_count(&two_refs), 1);
    assert_eq!(Arc::weak_count(&two_refs), 2);

    let two_refs1 = Weak::upgrade(&two_refs.inner1).unwrap();
    assert!(Arc::ptr_eq(&two_refs, &two_refs1));

    let two_refs2 = Weak::upgrade(&two_refs.inner2).unwrap();
    assert!(Arc::ptr_eq(&two_refs, &two_refs2));

    assert_eq!(Arc::strong_count(&two_refs), 3);
    assert_eq!(Arc::weak_count(&two_refs), 2);
}

/// Test for Arc::drop bug (https://github.com/rust-lang/rust/issues/55005)
#[test]
#[cfg(miri)] // relies on Stacked Borrows in Miri
fn arc_drop_dereferenceable_race() {
    // The bug seems to take up to 700 iterations to reproduce with most seeds (tested 0-9).
    for _ in 0..750 {
        let arc_1 = Arc::new(());
        let arc_2 = arc_1.clone();
        let thread = thread::spawn(|| drop(arc_2));
        // Spin a bit; makes the race more likely to appear
        let mut i = 0;
        while i < 256 {
            i += 1;
        }
        drop(arc_1);
        thread.join().unwrap();
    }
}

#[test]
fn arc_doesnt_leak_allocator() {
    let counter = AtomicUsize::new(0);

    {
        let arc: Arc<dyn Any + Send + Sync, _> = Arc::new_in(5usize, AllocCanary::new(&counter));
        drop(arc.downcast::<usize>().unwrap());

        let arc: Arc<dyn Any + Send + Sync, _> = Arc::new_in(5usize, AllocCanary::new(&counter));
        drop(unsafe { arc.downcast_unchecked::<usize>() });

        let arc = Arc::new_in(MaybeUninit::<usize>::new(5usize), AllocCanary::new(&counter));
        drop(unsafe { arc.assume_init() });

        let arc: Arc<[MaybeUninit<usize>], _> =
            Arc::new_zeroed_slice_in(5, AllocCanary::new(&counter));
        drop(unsafe { arc.assume_init() });
    }

    assert_eq!(counter.load(SeqCst), 0);
}