I came up with this (quite ugly) implementation:

struct Vec3 {
    union {
        float my_vec[1];
        float x;
    };

    float y;
    float z;
};
This will probably be flagged by sanitizers and some compilers as unsafe,
but I believe it's standard-compliant and does what's asked for.





On Fri, Mar 8, 2024 at 2:53 PM Jens Maurer via Std-Proposals <
std-proposals_at_[hidden]> wrote:

>
>
> On 08/03/2024 00.23, veronica alphonso via Std-Proposals wrote:
> > The issue i see about making anonymous structs/classes standard, is that
> now something as confusing as this could be allowed:
> >
> > // on the global namespace...
> > struct
> > {
> > int x;
> > };
> >
> > void foo()
> > {
> > .x = 42;
> > // what? so x is some kind of weird SDM/global now?
>
> What is "SDM"?
>
> > // what is its lifetime?
> > }
>
> We already have anonymous unions, suitably restricted to being
> members of classes only.
>
> Given those restrictions, how much of the problem space would
> anonymous structs address?
>
> Jens
>
>
> > El jue, 7 mar 2024 a las 23:17, Sebastian Wittmeier via Std-Proposals (<
> std-proposals_at_[hidden] <mailto:std-proposals_at_[hidden]>>)
> escribió:
> >
> > __
> >
> > Dear Veronica,
> >
> > what about your mentioned alternative of anonymous unions and
> structs?
> >
> > They could be made standard-compliant.
> >
> > And would need less language changes.
> >
> >
> >
> > Would they have problems with UB due to which element is the active
> one? When used in your use case?
> >
> >
> >
> > Best regards,
> >
> > Sebastian
> >
> >
> > -----Ursprüngliche Nachricht-----
> > *Von:* veronica alphonso via Std-Proposals <
> std-proposals_at_[hidden] <mailto:std-proposals_at_[hidden]>>
> > *Gesendet:* Do 07.03.2024 23:55
> > *Betreff:* [std-proposals] Subscript aliasing
> > *An:* std-proposals_at_[hidden] <mailto:
> std-proposals_at_[hidden]>;
> > *CC:* veronica alphonso <verodeving_at_[hidden] <mailto:
> verodeving_at_[hidden]>>;
> > In C++ there isn't a standard-compliant way of creating named
> aliases of c-like array elements. In certain contexts, it is preferred to
> access these these array elements with a named identifier that is bounded
> to that particular array entry, e.g:
> >
> > union
> > {
> > float my_vec[3];
> > struct
> > {
> > float x, y, z;
> > };
> > };
> >
> > However, anonymous structs/classes are only
> >
> > --
> > Std-Proposals mailing list
> > Std-Proposals_at_[hidden] <mailto:
> Std-Proposals_at_[hidden]>
> > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals <
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals>
> >
> >
> > --
> > Std-Proposals mailing list
> > Std-Proposals_at_[hidden] <mailto:
> Std-Proposals_at_[hidden]>
> > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals <
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals>
> >
> >
> --
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>

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