// run-pass
// alloc::heap::reallocate test.
//
// Ideally this would be revised to use no_std, but for now it serves
// well enough to reproduce (and illustrate) the bug from #16687.

#![feature(allocator_api)]
#![feature(slice_ptr_get)]

use std::alloc::{handle_alloc_error, Allocator, Global, Layout};
use std::ptr::{self, NonNull};

fn main() {
    unsafe {
        assert!(test_triangle());
    }
}

unsafe fn test_triangle() -> bool {
    static COUNT: usize = 16;
    let mut ascend = vec![ptr::null_mut(); COUNT];
    let ascend = &mut *ascend;
    static ALIGN: usize = 1;

    // Checks that `ascend` forms triangle of ascending size formed
    // from pairs of rows (where each pair of rows is equally sized),
    // and the elements of the triangle match their row-pair index.
    unsafe fn sanity_check(ascend: &[*mut u8]) {
        for i in 0..COUNT / 2 {
            let (p0, p1, size) = (ascend[2 * i], ascend[2 * i + 1], idx_to_size(i));
            for j in 0..size {
                assert_eq!(*p0.add(j), i as u8);
                assert_eq!(*p1.add(j), i as u8);
            }
        }
    }

    static PRINT: bool = false;

    unsafe fn allocate(layout: Layout) -> *mut u8 {
        if PRINT {
            println!("allocate({:?})", layout);
        }

        let ptr = Global.allocate(layout).unwrap_or_else(|_| handle_alloc_error(layout));

        if PRINT {
            println!("allocate({:?}) = {:?}", layout, ptr);
        }

        ptr.as_mut_ptr()
    }

    unsafe fn deallocate(ptr: *mut u8, layout: Layout) {
        if PRINT {
            println!("deallocate({:?}, {:?}", ptr, layout);
        }

        Global.deallocate(NonNull::new_unchecked(ptr), layout);
    }

    unsafe fn reallocate(ptr: *mut u8, old: Layout, new: Layout) -> *mut u8 {
        if PRINT {
            println!("reallocate({:?}, old={:?}, new={:?})", ptr, old, new);
        }

        let memory = if new.size() > old.size() {
            Global.grow(NonNull::new_unchecked(ptr), old, new)
        } else {
            Global.shrink(NonNull::new_unchecked(ptr), old, new)
        };

        let ptr = memory.unwrap_or_else(|_| handle_alloc_error(new));

        if PRINT {
            println!("reallocate({:?}, old={:?}, new={:?}) = {:?}", ptr, old, new, ptr);
        }
        ptr.as_mut_ptr()
    }

    fn idx_to_size(i: usize) -> usize {
        (i + 1) * 10
    }

    // Allocate pairs of rows that form a triangle shape.  (Hope is
    // that at least two rows will be allocated near each other, so
    // that we trigger the bug (a buffer overrun) in an observable
    // way.)
    for i in 0..COUNT / 2 {
        let size = idx_to_size(i);
        ascend[2 * i] = allocate(Layout::from_size_align(size, ALIGN).unwrap());
        ascend[2 * i + 1] = allocate(Layout::from_size_align(size, ALIGN).unwrap());
    }

    // Initialize each pair of rows to distinct value.
    for i in 0..COUNT / 2 {
        let (p0, p1, size) = (ascend[2 * i], ascend[2 * i + 1], idx_to_size(i));
        for j in 0..size {
            *p0.add(j) = i as u8;
            *p1.add(j) = i as u8;
        }
    }

    sanity_check(&*ascend);
    test_1(ascend); // triangle -> square
    test_2(ascend); // square -> triangle
    test_3(ascend); // triangle -> square
    test_4(ascend); // square -> triangle

    for i in 0..COUNT / 2 {
        let size = idx_to_size(i);
        deallocate(ascend[2 * i], Layout::from_size_align(size, ALIGN).unwrap());
        deallocate(ascend[2 * i + 1], Layout::from_size_align(size, ALIGN).unwrap());
    }

    return true;

    // Test 1: turn the triangle into a square (in terms of
    // allocation; initialized portion remains a triangle) by
    // realloc'ing each row from top to bottom, and checking all the
    // rows as we go.
    unsafe fn test_1(ascend: &mut [*mut u8]) {
        let new_size = idx_to_size(COUNT - 1);
        let new = Layout::from_size_align(new_size, ALIGN).unwrap();
        for i in 0..COUNT / 2 {
            let (p0, p1, old_size) = (ascend[2 * i], ascend[2 * i + 1], idx_to_size(i));
            assert!(old_size < new_size);
            let old = Layout::from_size_align(old_size, ALIGN).unwrap();

            ascend[2 * i] = reallocate(p0, old.clone(), new.clone());
            sanity_check(&*ascend);

            ascend[2 * i + 1] = reallocate(p1, old.clone(), new.clone());
            sanity_check(&*ascend);
        }
    }

    // Test 2: turn the square back into a triangle, top to bottom.
    unsafe fn test_2(ascend: &mut [*mut u8]) {
        let old_size = idx_to_size(COUNT - 1);
        let old = Layout::from_size_align(old_size, ALIGN).unwrap();
        for i in 0..COUNT / 2 {
            let (p0, p1, new_size) = (ascend[2 * i], ascend[2 * i + 1], idx_to_size(i));
            assert!(new_size < old_size);
            let new = Layout::from_size_align(new_size, ALIGN).unwrap();

            ascend[2 * i] = reallocate(p0, old.clone(), new.clone());
            sanity_check(&*ascend);

            ascend[2 * i + 1] = reallocate(p1, old.clone(), new.clone());
            sanity_check(&*ascend);
        }
    }

    // Test 3: turn triangle into a square, bottom to top.
    unsafe fn test_3(ascend: &mut [*mut u8]) {
        let new_size = idx_to_size(COUNT - 1);
        let new = Layout::from_size_align(new_size, ALIGN).unwrap();
        for i in (0..COUNT / 2).rev() {
            let (p0, p1, old_size) = (ascend[2 * i], ascend[2 * i + 1], idx_to_size(i));
            assert!(old_size < new_size);
            let old = Layout::from_size_align(old_size, ALIGN).unwrap();

            ascend[2 * i + 1] = reallocate(p1, old.clone(), new.clone());
            sanity_check(&*ascend);

            ascend[2 * i] = reallocate(p0, old.clone(), new.clone());
            sanity_check(&*ascend);
        }
    }

    // Test 4: turn the square back into a triangle, bottom to top.
    unsafe fn test_4(ascend: &mut [*mut u8]) {
        let old_size = idx_to_size(COUNT - 1);
        let old = Layout::from_size_align(old_size, ALIGN).unwrap();
        for i in (0..COUNT / 2).rev() {
            let (p0, p1, new_size) = (ascend[2 * i], ascend[2 * i + 1], idx_to_size(i));
            assert!(new_size < old_size);
            let new = Layout::from_size_align(new_size, ALIGN).unwrap();

            ascend[2 * i + 1] = reallocate(p1, old.clone(), new.clone());
            sanity_check(&*ascend);

            ascend[2 * i] = reallocate(p0, old.clone(), new.clone());
            sanity_check(&*ascend);
        }
    }
}