Re: [Qemu-devel] [PATCH v2] use _Static_assert in QEMU_BUILD_BUG_ON

[Andreas Grapentin <andreas@grapentin.org>]

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The missing ! is because I generated the error messages by inverting the
condition and then forgot to change it back. I can send a v3 if you
like.

Thanks for being patient with me.

-A


On Tue, Mar 14, 2017 at 12:43:56PM -0500, Eric Blake wrote:
> On 03/14/2017 11:59 AM, Andreas Grapentin wrote:
> > QEMU_BUILD_BUG_ON should use C11's _Static_assert, if the compiler supports it,
> > to provide more readable messages on failure.
> 
> > 
> > with _Static_assert:
> > 
> >> In file included from /qemu/include/qemu/osdep.h:36:0,
> >>                  from /qemu/qga/commands.c:13:
> >> /qemu/qga/commands.c: In function ‘qmp_guest_exec_status’:
> >> /qemu/include/qemu/compiler.h:94:30: error: static assertion failed: "not expecting: sizeof(*&gei->finished) > sizeof(void *)"
> >>  #define QEMU_BUILD_BUG_ON(x) _Static_assert((x), #x)
> 
> Manual copy-and-paste? Because this is missing the ! present in the
> actual definition...
> 
> >>                               ^
> >> /qemu/include/qemu/atomic.h:146:5: note: in expansion of macro ‘QEMU_BUILD_BUG_ON’
> >>      QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *));   \
> >>      ^~~~~~~~~~~~~~~~~
> >> /qemu/include/qemu/atomic.h:417:5: note: in expansion of macro ‘atomic_load_acquire’
> >>      atomic_load_acquire(ptr)
> >>      ^~~~~~~~~~~~~~~~~~~
> >> /qemu/qga/commands.c:160:21: note: in expansion of macro ‘atomic_mb_read’
> >>      bool finished = atomic_mb_read(&gei->finished);
> >>                      ^~~~~~~~~~~~~~
> > 
> > Signed-off-by: Andreas Grapentin <andreas@grapentin.org>
> > ---
> 
> > +++ b/include/qemu/compiler.h
> > @@ -90,7 +90,9 @@
> >          int:(x) ? -1 : 1; \
> >      }
> >  
> > -#ifdef __COUNTER__
> > +#if defined(CONFIG_STATIC_ASSERT)
> > +#define QEMU_BUILD_BUG_ON(x) _Static_assert(!(x), "not expecting: " #x)
> 
> ...here.
> 
> But that's trivial, if the maintainer would like to correct the commit
> message.
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
> 
> 
> -- 
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
> 




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