On Thu, Mar 20, 2025 at 5:39 PM Hans Åberg via Std-Proposals
<std-proposals_at_[hidden]> wrote:
>
>
> > On 20 Mar 2025, at 22:19, Thiago Macieira <thiago_at_[hidden]> wrote:
> >
> > 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?
>
> The standard has no control over what compiler writers will do.
>
> >>> 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.
>
> The intended design is for use in the standard library.

Define "use in the standard library". Are you saying that future
versions of the standard should declare functions to be
"unimplemented"? Or is this just a temporary tool for use during
upgrades to the implementation of the standard library.

Because if it's the latter... then implementers of the standard
library can use whatever compiler-specific features they want. If this
isn't something that a normal user is expected to ever use, then
there's no point in adding it to the language. If implementers of the
standard library legitimately need this, they can request
compiler-specific functionality to do it.