C++11 attributes for C11 (was Re: [PATCH] Generalized attribute support)

[Alp Toker]

On 22/04/2014 21:45, Nico Weber wrote:
> On Sat, Apr 19, 2014 at 4:05 PM, Alp Toker <alp at nuanti.com 
> <mailto:alp at nuanti.com>> wrote:
>
>     Small update for the list..
>
>     We discussed this at LLVM Europe 2014 and came to the conclusion
>     that we might as well offer the feature behind an -f flag.
>
>     This should satisfy user requests for C++11-style attributes in
>     C11 without prejudicing any standards process. Thanks to the many
>     detailed use-cases people sent in that have made me more
>     comfortable picking this up again.
>
>
> Are these use-cases visible anywhere?

So, I brought this up at the FOSDEM clang talk and some folks came up in 
person who were looking for this attribute syntax in non-C++11 dialetcs, 
or rolling their own. The ones I remember are:

PENCIL C extension team (Sven K?)
Machine Guided Energy Efficient Compilation (MAGEEC)
Some kernel people

There were also some promising leads on-list on the original thread 
including Aaron's team at CERT I believe.

That's about the sum of my record-keeping abilities :-)

Alp.



>
>     So, I've got a slightly improved version of the patch and will aim
>     to rebase and post it to the list for review in the coming weeks.
>
>     All we need now is great name for the -f flag ;-)
>
>     Alp.
>
>
>     On 15/01/2014 20:44, Alp Toker wrote:
>
>
>         On 15/01/2014 20:29, Richard Smith wrote:
>
>             On Wed Jan 15 2014 at 3:42:08 AM, Alp Toker
>             <alp at nuanti.com <mailto:alp at nuanti.com>
>             <mailto:alp at nuanti.com <mailto:alp at nuanti.com>>> wrote:
>
>
>                 On 15/01/2014 06:04, Nico Weber wrote:
>                 > Does gcc allow this for C? Is C planning on
>             standardizing this?
>
>                 The impression I get is that everybody's doing it but
>             nobody's talking
>                 about it. Yet.
>
>
>             Weird. The impression I get is that nobody is doing it (at
>             least, not publically).
>
>
>         People said they were patching internally to use new security
>         and optimization attributes, and presumably there are others
>         ("nobody's talking about it"). Seems a reasonable use case.
>
>
>             What if a future revision of a standard we care about
>             (maybe C, OpenMP, OpenCL, CUDA, ...) standardizes a
>             *different* meaning for square brackets? Code that used
>             our extension would be in trouble.
>
>
>         This is a great reason to hold back from switching it on globally.
>
>         If we don't have "nudge" power in getting this as a de-facto
>         C1y feature it becomes less interesting.
>
>
>             This isn't even purely theoretical -- Objective-C does
>             this, and it is essentially only by luck that it's
>             possible to disambiguate this fully. As another example,
>             if C17 took C++'s lambdas but not its attributes, we'd run
>             into some amount of trouble with expressions like
>
>              int x[ [] { ... } () ];
>
>             (which is an ill-formed attribute under the C++11 rules).
>
>
>         It'd be far from the worst disambiguation we have in-tree.
>
>         Objective-C disambiguation is working fine with the C11
>         extension enabled for what it's worth.
>
>         I'm withdrawing the patch, there are probably more useful
>         things to be working on.
>
>         Tentatively setting a date to revisit this in a years time or
>         after gcc implements, whichever comes first, when there might
>         be a clearer way forward.
>
>         Alp.
>
>
>
>     -- 
>     http://www.nuanti.com
>     the browser experts
>
>

-- 
http://www.nuanti.com
the browser experts