investigate `Box::new_in` issue with custom allocator

[hannahfluch]

Creating a new box on the heap with a reference to the global allocator panics with the following error message:

unsafe precondition(s) violated: ptr::read requires that the pointer argument is aligned and non-null

_ = Box::new_in(0, &Global);

Passing the global allocator directly makes the allocation work smoothly:
_ = Box::new_in(0, Global);

The problem may be related to this or this issue. Although, they have seemingly been resolved.

Testing with this heap allocator does not solve the problem.

[hannahfluch]

Using this heap allocator does not fix the problem either. The issue does not exist in a different no-std environment.

[hannahfluch]

The panic occurs during the Box::assume_init() call. While calling Box::into_raw_with_allocator() .

[hannahfluch]

minimal reproduction:

fn test_alloc<A: Allocator>(myalloc: A) -> A {
    unsafe { core::ptr::read(&myalloc) }
}

successful:

 _ = test_alloc(Global);

panic:

_ = test_alloc(&Global);

[hannahfluch]

The issue is a misaligned kernel stack.

[hannahfluch]

This will be fixed as part of #5

[hannahfluch]

d0de740 resolves this and will be merged into main.