It is just to following the C++ practise to avoid adding keywords.

It makes sense though if one thinks of it refers to the original function that is unimplemented, and is easy to remember.

It is useful to override global operator new when using a GC.

> On 20 Mar 2025, at 19:11, Thiago Macieira via Std-Proposals <std-proposals_at_[hidden]> wrote:
>
> On Thursday, 20 March 2025 10:15:12 Pacific Daylight Time Hans Åberg via Std-
> Proposals wrote:
>> If a declaration is marked “unimplemented”, then also the definition must
>> have it. If implemented in a later compiler version, then this label is
>> reoved, and the linker chooses the definition without the label.
>
> An unimplemented implementation is an oxymoron. Instead, I'd recommend you add
> another attribute to override the unimplemented marker and say it has been
> implemented.
>
>> A similar linker override already exists for global operator new.
>
> Which is very special and does not work across DLLs on Windows. Do not copy
> this precedent. This is even less workable because it requires linker changes.