[Bug c++/68257] Reject empty abi_tag attribute on inline namespace

[sbergman at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68257

--- Comment #3 from Stephan Bergmann <sbergman at redhat dot com> ---
(In reply to Jakub Jelinek from comment #1)
> So, if there is a bug, I'd say just that this is not well documented.

See the attached Fix-abi_tag-doc.patch.


(In reply to Jonathan Wakely from comment #2)
> although I thought the correct syntax in that case was:
> 
> inline namespace n __attribute__((__abi_tag__)) {}
> 
> i.e. no parentheses after __abi_tag__

Would that be considered something worthwhile to change, to only accept

  __attribute__((__abi_tag__))

but reject

  __attribute__((__abi_tag__()))

?