[Bug c++/102397] New: Documentation of attribute syntax does not discuss C++11 / C23 attribute syntax

[Bug c++/102397] New: Documentation of attribute syntax does not discuss C++11 / C23 attribute syntax

[dangelog at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102397

            Bug ID: 102397
           Summary: Documentation of attribute syntax does not discuss
                    C++11 / C23 attribute syntax
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dangelog at gmail dot com
  Target Milestone: ---

Hi,

The available documentation for attributes syntax 

https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute-Syntax

does not mention at all the possibility that in C++11 (and, I imagine, in C23)
one can specify any GCC-specific attribute using a [[gnu::attribute]] attribute
specifier, and not only the GCC-specific __attribute__((attribute)) syntax.

I think it would be worth mentioning in there that this is actually OK and
fully supported.

[Bug c++/102397] Documentation of attribute syntax does not discuss C++11 / C23 attribute syntax

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102397

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2021-09-18
     Ever confirmed|0                           |1

[Bug c++/102397] Documentation of attribute syntax does not discuss C++11 / C23 attribute syntax

[sandra at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102397

sandra at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sandra at gcc dot gnu.org

--- Comment #1 from sandra at gcc dot gnu.org ---
I committed a patch a few months ago to say that the new C++/C standard
attribute syntax is supported with a gnu:: prefix, so at least the
originally-reported problem has already been fixed.

However, all the examples still use the old syntax.  Given that there is an
awful lot of legacy code using the old syntax already out there, examples are
useful in helping people grok what it means, but at some point we probably want
to encourage people to use the new syntax in new code for all the usual reasons
why it's better to do things in a standard way, and use it also as the primary
form for documentation.  

OTOH, I don't think we're quite there yet.  Presently the manual describes C23
support as "experimental and incomplete" and says the default C language
dialect is -std=gnu17.  My sense is that it's not appropriate to tell users to
make the switch until GCC's default dialect is advanced to something based on
C23.

So I'm going to leave this issue open for now instead of closing it as fixed,
as a reminder that there is still more work to be done here a little farther
down the road.