On Thursday, 20 March 2025 10:08:57 Pacific Daylight Time Hans Åberg wrote:
> > But the C++ feature should not rely on developers using pragma, because
> > the
> > specific pragmas are not part of the standard. The feature must assume
> > that all warnings will be dealt with as "this must be fixed" and
> > developers will just change the code.
>
> If they decide compile that way, it is their business, not of the standard.
> The standard does not specify to issue warnings in the compile, only giving
> some cases where it might be appropriate.

Which means a perfectly-compliant compiler may issue no warning on the use of
[[unimplemented]]. What's the difference between that and having no attribute?

> > That means this feature's only remaining use is that an [[unimplemented]]
> > declaration can later be overridden as implemented. You'll need to explain
> > why this can't simply be done by changing the first declaration and how
> > that is not fragile in the first place. What happens if the declaration
> > order changes?
>
> The same. But if used in a standard library, the order will not change.

The most common use will not the in the Standard Library. Please design it
with the most common use-case in mind.

> > If it's a temporary thing, I can name my function however I want.
>
> Indeed, but the guy who wrote it leaves, and later when the implementation
> is added, others will have to figure how to fix it instead of doing more
> important things. A similar question arose on a 600 k lines of C++ code
> project.

And fixing [[unimplemented]] is still work. If the original party adds the
function, now we have two definitions and the linking may fail (ODR violations
are IFNDR) - it will fail if linking statically.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Principal Engineer - Intel DCAI Platform & System Engineering