On Friday, 27 June 2025 at 19:55:30 UTC, WraithGlade wrote:
Thanks for responding to my question and for your time, etc.
I was aware of `align` but as far as I am aware it is
orthogonal to what I'm asking about. The Andrei book says that
D automatically rearranges members of `class`s in memory to
avoid wasting memory due to padding between members whose width
is less than the native CPU word size alignment, whereas
`struct`s are left as is (meaning the members aren't reordered
for alignment padding optimization).
The `align` command specifies alignments but doesn't seem
relevant to automatic rearranging of members for classes.
I'm not sure if D does that or not anymore, since (as you said)
it has been a long while since that book was published.
I think you're referring to [this description in the
spec](https://dlang.org/spec/class.html#fields):
The D compiler is free to rearrange the order of fields in a
class to optimally pack them. Consider the fields much like the
local variables in a function - the compiler assigns some to
registers and shuffles others around all to get the optimal
stack frame layout. This frees the code designer to organize
the fields in a manner that makes the code more readable rather
than being forced to organize it according to machine
optimization rules. Explicit control of field layout is
provided by struct/union types, not classes.
