Why compare `align_of`?

[rise0chen]

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Test {
    a: u8,
    b: u8,
    c: u8,
    d: u8,
}
fn main() {
    println!("align: {}", core::mem::align_of::<Test>());
    println!("size: {}", core::mem::size_of::<Test>());
}

Size of the struct is 4, align of the struct is 1. The condition is not met.

[rise0chen]

I think Atomic<Test > can be converted to AtomicU32

[Amanieu]

You can use #[repr(align(4))] on your struct to ensure the alignment is sufficient. This is required since this crate will unsafely access your struct as an AtomicU32.

[rise0chen]

transmute don't require alignment, how about replace transmute_copy by transmute?

[Amanieu]

This crate isn't actually transmuting though, it's casting a pointer to your type to a pointer to AtomicU32 and accessing it as an AtomicU32 in-place. This requires that your type be suitably aligned for an AtomicU32.