Why can't we derive struct's?
schveiguy at gmail.com
Thu Dec 20 14:55:45 UTC 2018
On 12/20/18 3:15 AM, Manu wrote:
> On Wed, Dec 19, 2018 at 7:45 PM Walter Bright via Digitalmars-d
> <digitalmars-d at puremagic.com> wrote:
>> On 12/19/2018 5:40 PM, Manu wrote:
>> > static if (Base.tupleof.length == 0)
>> static if (Base.sizeof == 0)
> Empty struct has sizeof == 1 no? It certainly takes that many bytes as
> a member, and that 1 byte is naturally padded out to the alignment of
> the following member.
Yes, it does take 1 byte. I believe the reasoning was so it could have a
unique address and be used in an array.
It's the same in C++ as well, according to the Internet (except for the
base class optimization allowance). Note that C++ compilers aren't
*required* to implement this.
The difference between inheritance and manual inheritance (i.e. alias
this and a member), is that with true inheritance there is no member
that has to have it's own distinct address, so it's allowed to take up 0
But I would expect your boilerplate could be handled via mixin template
pretty easily, then it becomes:
That it takes up the one alias this slot is a bummer, but really we
should implement multiple-alias-this and that problem would be solved.
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