Re: _Noreturn and draft C23

[Bruno Haible]

Hi Paul,

> That reminds me, we're in a sticky situation about _Noreturn for another 
> reason.
> 
> Draft C23 requires [[noreturn]] before "extern" and states that 
> _Noreturn is obsolescent. It's plausible that a future C version will 
> drop the requirement to support the _Noreturn keyword. If that happens, 
> "#define _Noreturn [[noreturn]]" won't be a valid workaround unless 
> people write "_Noreturn extern" instead of "extern _Noreturn", and 
> similarly for "_Noreturn static" etc.
> 
> Should we change Gnulib code and put _Noreturn first in its declarations 
> now, proactively? This might help future-proof the code, and get people 
> used to putting directives first.

For the .h files, we have already started doing so, in order to
maintain C++ compatibility:
  <https://lists.gnu.org/archive/html/bug-gnulib/2020-02/msg00008.html>

For the other files, I suggest to wait until it becomes clear how ISO C
will evolve in this aspect. They could un-obsolete the '_Noreturn' keyword.
They could allow [[noreturn]] to be used before _or_ after the 'extern'
or 'static' keyword. They could make other changes that I can't imagine.
We have seen (with the K&R C declaration removal, as well as with %b and %B
just last week) that the way the standard evolves is just unpredictable.
When a new ISO C draft is in ballot phase, we still have a year or more
of time to adapt our code. There's no pressure on us to do these things
2 or 10 years in advance.

Bruno