[Issue 16508] Alignment of class members is not respected. Affects new, scoped and classInstanceAlignment.

d-bugmail at puremagic.com d-bugmail at puremagic.com
Sun Aug 8 16:06:38 UTC 2021


--- Comment #6 from Max Samukha <maxsamukha at gmail.com> ---
(In reply to kinke from comment #5)
> (In reply to Max Samukha from comment #4)
> > I'm curious why you chose to nitpick - it's unlikely you didn't understand
> > what I meant.
> Just stumbled upon this issue and wanted to correct this -
> `classInstanceSize` doesn't need a fix.
> > Class instance types exist implicitly and are commonly represented by
> > structs.  The return type of std.typecons.scoped is an example, as you know.
> > It is reasonable to expect arrays (and, in general, sequentially stored
> > objects) of such structs to be usable.
> A field like `align(C.alignof) void[__traits(classInstanceSize, C)] buffer`
> should make sure there's appropriate padding, solely based on the align
> declaration, which is required anyway and apparently does need fixing.

(I assume you meant align(classInstanceAlignment!C), which currently produces
wrong results due to this bug)

I'm sorry to disagree. __traits(classInstanceSize) should return the stride of
an array of class instances, similarly to what .sizeof does for structs.


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