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

[Ian Campbell <ian.campbell@citrix.com>]

On Wed, 2015-10-07 at 00:31 -0600, Jan Beulich wrote:
> > > > On 06.10.15 at 19:25, <julien.grall@citrix.com> wrote:
> > On 05/10/15 11:31, Jan Beulich wrote:
> > > > > > On 04.10.15 at 21:24, <julien.grall@citrix.com> 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]
> > > 
> > > Actually, it's worse than that - typeof() is a gcc extension, and we
> > > shouldn't use extensions in public headers without at least having
> > > alternative code for not gcc compatible compilers in place. In fact
> > > we should probably aim at removing the exclusion of public/arch-%
> > > in the ANSI conformance check; IIRC I had to add it because things
> > > wouldn't build without, but with the (then forgotten) goal of dealing
> > > with this properly later on.
> > 
> > I don't see how header.chk would have catch my issue. The problem is in
> > the macro set_xen_guest_handle_raw which is not used within the headers
> > (except by set_xen_guest_handle which is not used at all).
> > 
> > It may be worth to add a dummy .c which call the macros to check they
> > are ANSI compliant.
> 
> Hmm, true, conformance of macros isn't being checked right now
> (i.e. we only verify that the header as such compiles, not that
> everything in the header can be used). A manually created source
> would help only to some degree, as it would need to be kept up to
> date with future additions. I.e. the long term solution probably
> ought to be an at least partially machine generated source file

It ought to be possible to at least automatically check that every
    #define ([A-Za-z_]+)
is matched by a corresponding $1 in the .c file.

> . I added this to my todo list (but towards the end of it).

FWIW I have a similar issue with the headers checks for my split up
libxenctrl stable libraries series, and it is in a similar place on my todo
list...

Ian.