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#![feature(alloc_error_hook, allocator_api)]
use std::alloc::{AllocError, Allocator, Layout, System, set_alloc_error_hook};
use std::collections::VecDeque;
use std::panic::{AssertUnwindSafe, catch_unwind};
use std::ptr::NonNull;
#[test]
#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
fn test_shrink_to_unwind() {
// This tests that `shrink_to` leaves the deque in a consistent state when
// the call to `RawVec::shrink_to_fit` unwinds. The code is adapted from #123369
// but changed to hopefully not have any UB even if the test fails.
struct BadAlloc;
unsafe impl Allocator for BadAlloc {
fn allocate(&self, l: Layout) -> Result<NonNull<[u8]>, AllocError> {
// We allocate zeroed here so that the whole buffer of the deque
// is always initialized. That way, even if the deque is left in
// an inconsistent state, no uninitialized memory should be accessed.
System.allocate_zeroed(l)
}
unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
unsafe { System.deallocate(ptr, layout) }
}
unsafe fn shrink(
&self,
_ptr: NonNull<u8>,
_old_layout: Layout,
_new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
Err(AllocError)
}
}
set_alloc_error_hook(|_| panic!("alloc error"));
let mut v = VecDeque::with_capacity_in(15, BadAlloc);
v.push_back(1);
v.push_front(2);
// This should unwind because it calls `BadAlloc::shrink` and then `handle_alloc_error` which unwinds.
assert!(catch_unwind(AssertUnwindSafe(|| v.shrink_to_fit())).is_err());
// This should only pass if the deque is left in a consistent state.
assert_eq!(v, [2, 1]);
}
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