Function align_of_val_raw

pub const unsafe fn align_of_val_raw<T: ?Sized>(val: *const T) -> usize

🔬This is a nightly-only experimental API. (layout_for_ptr #69835)

Returns the ABI-required minimum alignment of the type of the value that val points to in bytes.

Every reference to a value of the type T must be a multiple of this number.

Safety

This function is only safe to call if the following conditions hold:

• If T is Sized, this function is always safe to call.
• If the unsized tail of T is:
  • a slice, then the length of the slice tail must be an initialized integer, and the size of the entire value (dynamic tail length + statically sized prefix) must fit in isize. For the special case where the dynamic tail length is 0, this function is safe to call.
  • a trait object, then the vtable part of the pointer must point to a valid vtable acquired by an unsizing coercion, and the size of the entire value (dynamic tail length + statically sized prefix) must fit in isize.
  • an (unstable) extern type, then this function is always safe to call, but may panic or otherwise return the wrong value, as the extern type’s layout is not known. This is the same behavior as align_of_val on a reference to a type with an extern type tail.
  • otherwise, it is conservatively not allowed to call this function.

Examples

#![feature(layout_for_ptr)]
use std::mem;

assert_eq!(4, unsafe { mem::align_of_val_raw(&5i32) });