On 01/19/2017 03:07 PM, Michael S. Tsirkin wrote: > QEMU_BUILD_BUG_ON uses a typedef in order to be safe > to use outside functions, but sometimes it's useful > to have a version that can be used within an expression. > Following what Linux does, introduce QEMU_BUILD_BUG_ON_ZERO > that return zero after checking condition at build time. > > Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > --- > include/qemu/compiler.h | 3 +++ > 1 file changed, 3 insertions(+)
Reviewed-by: Eric Blake <ebl...@redhat.com> > > diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h > index c6f673e..8271eab 100644 > --- a/include/qemu/compiler.h > +++ b/include/qemu/compiler.h > @@ -92,6 +92,9 @@ > #define QEMU_BUILD_BUG_ON(x) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \ > glue(qemu_build_bug_on__, __LINE__) __attribute__((unused)) > > +#define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(QEMU_BUILD_BUG_ON_STRUCT(x)) - \ > + sizeof(QEMU_BUILD_BUG_ON_STRUCT(x))) Although this should be equally effective, with less typing: #define QEMU_BUILD_BUG_ON_ZERO(x) (!sizeof(QEMU_BUILD_BUG_ON_STRUCT(x))) -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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