> On 18 Mar 2025, at 20:10, Marcin Jaczewski <marcinjaczewski86_at_[hidden]> wrote:
>
> wt., 18 mar 2025 o 19:14 Hans Åberg via Std-Proposals
> <std-proposals_at_[hidden]> napisał(a):
>>
>> I independently suggested the same thing on the GCC Help list:
>>
>> A compiler may have declarations that leave a series of components undefined. In the case of GCC, this happens with float128_t on MacOS, because it relies on the native C library which comes from Clang and does not have this type. It is fixable by relying on another float128 library if left undefined, but if marked deleted, it can't be fixed.
>>
>> Semantically, delete means that the function should not be implemented, whereas unimplemented means that the function may be implemented.
>>
>> So if the compiler finds a function marked unimplemented, it might issue a warning, but overridden if it also finds a version (declared or defined) of the same function without it, in which case no warning is issued.
>>
>
> How and when "find" it?

Just declarations and definitions.

>
> Consider this code:
>
> ```
> void foo() unimplemented;
>
> int main()
> {
> foo();
> }
> ```
>
> Should this code compile or not? when exactly should it compiler and
> when it should not?

If it is a warning, it compiles with a diagnostic. But if you think it is safe, an error may be required.