On 6/11/22 11:03, Alejandro Colomar via Gcc wrote:
> Hi Jonathan,
>
> On 6/11/22 00:47, Jonathan Wakely wrote:
>> Well, I'd argue the same reasons to remove it from C++. Don't
know how
>> useful that feature is for C++, though. I bet not much, but am
not an
>> expert in the language.
>>
>>
>> It's used in libstdc++ because I couldn't get an attribute to work
in any other location, because it isn't valid at other positions in a
constrained function template. So no, we can't remove it from C++.
>>
>
> Hmm, okay, not removable in C++. I'm curious about the specific line
of code, if you have it around and could link to it. But C++ is huge, so
anything is to be expected :)
>
>>
>>
>>
>> But, are we sure we want to add this to C? You know how difficult
>> is to
>> revert mistakes in C, as opposed to C++, where additions and
>> deprecations are more common.
>>
>>
>> To the core language grammar? Are you sure about that?
>
> Well, everything is relative.
>
> libstdc++ additions, deprecations (and undeprecations) are much more
common than in the core C++ language (e.g., the deprecation and later
undeprecation of <std*.h> headers).
>
> But breaking changes in the core C++ language are still more common
than in C, where (sadly) we still have the useless 'auto' for backwards
compatibility with dead languages, which would be nice in macros with
the meaning of __auto_type. Maybe in the 2050s? :P
>
>
> So, C++ needs this feature.
>
> Then in C, we don't need it (I've never seen code reusing the return
type to declare more than one function, and I hope to never see that
apart from theoretical investigation). `int foo(void), bar(void);`
seems a useless feature in the language to me, but maybe disallowing it
through an exception to the rules would complicate the wording more than
help, so if that's kept in the language, I'm fine with it.
>
> So we could, and also could not, bring the C++ attribute for that
useless feature.
>
> In C, I don't think that attribute position can have a useful use
case that can't be achieved by an attribute at the start of the
prototype, since the language is much simpler.
>
> Do we want to add a completely unnecessary feature, just for symmetry
with C++, even if it poses a danger of breaking (both human and script)
readability of function declarations/definitions, especially when hidden
in macros?
I actually don't get the trouble with this. Your tool already can't
parse declarations if they don't follow a certain coding style, so you
can just add this restriction to the coding style that's required.
> I still have the hope that if the feature is finally kept in C23,
absolutely no-one will ever use it, but then I question the introduction
in the first place.
Well in the same way, `int long signed const typedef long x;` is valid
C, and I do hope that nobody will ever use it, but I don't think we
should change C's grammar to disallow it.
>
> Cheers,
>
> Alex
>
Cheers,
Gabriel
