Function core::mem::align_of_val_raw
source · 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)Expand description
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
isSized
, 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
. - 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.
- 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
§Examples
#![feature(layout_for_ptr)]
use std::mem;
assert_eq!(4, unsafe { mem::align_of_val_raw(&5i32) });
Run