Re: [Xen-devel] [PATCH for-4.6] xen/public: arm: Use __typeof__ rather than typeof

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2015-10-23 at 08:16 -0600, Jan Beulich wrote:
> > > > On 23.10.15 at 15:58, <julien.grall@xxxxxxxxxx> wrote:
> > On 23/10/15 14:52, Jan Beulich wrote:
> > > > > > On 23.10.15 at 15:30, <ian.campbell@xxxxxxxxxx> wrote:
> > > > On Fri, 2015-10-23 at 14:13 +0100, Julien Grall wrote:
> > > > > Hi,
> > > > > 
> > > > > On 04/10/15 20:24, Julien Grall wrote:
> > > > > > The keyword typeof is not portable:
> > > > > > 
> > > > > > /usr/src/freebsd/sys/xen/hypervisor.h:93:2: error: implicit
> > > > > > declaration
> > > > > > of function 'typeof' is invalid in C99
> > > > > > [-Werror,-Wimplicit-function-declaration]
> > > > > 
> > > > > Ping? Aside the fact that other bits of the header may not be iso
> > > > > compliant, I still think this patch is valid.
> > > > 
> > > > Yes, I agree.
> > > > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > > > 
> > > > Jan, after your earlier comments are you happy to go ahead with
> > > > this for
> > > > now and sort the other possible issues separately?
> > > 
> > > Well - it's an improvement, sure, so I'm not intending to block it
> > > going in if no better way can be determined in its place right away.
> > > What makes me hesitant is that I'm not sure there indeed will be a
> > > follow up to this any time soon.
> > 
> > TBH, having a script which check the validity of the headers is not in
> > the top my todo list. Though it would be nice to have it.
> 
> No, the validating script is a nice-to-have, but nothing more. What
> I was referring to was a patch to drop the use of this gcc extension.

Then I'm confused. This patch turns a typeof into a __typeof__. In <
56126D8702000078000A80AC@xxxxxxxxxxxxxxxxxxxxxxx> you said "typeof() is a
gcc extension".

Are you now saying that __typeof__ also a gcc extension too?

I was under the impression that __typeof__ was standard (by some cxx at
least) and your mail reinforced that (possibly wrong) impression.

https://gcc.gnu.org/onlinedocs/gcc/Typeof.html also says that "If you are
writing a header file that must work when included in ISO C programs, write
__typeof__ instead of typeof", which also lead me to believe __typeof__ was
OK from this PoV.

Ian.

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