| Message ID | 1484771412-28024-4-git-send-email-mst@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
* Michael S. Tsirkin (mst@redhat.com) 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 <mst@redhat.com> > --- > include/qemu/compiler.h | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h > index 1a9eeb9..d2b05dd 100644 > --- a/include/qemu/compiler.h > +++ b/include/qemu/compiler.h > @@ -88,6 +88,8 @@ > #define QEMU_BUILD_BUG_ON(x) \ > typedef char glue(qemu_build_bug_on__,__LINE__)[(x)?-1:1] __attribute__((unused)) > > +#define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(int[(x)?-1:1]) - sizeof(int)) > + Yes, pretty much the same as: https://lists.gnu.org/archive/html/qemu-devel/2016-10/msg07090.html I'd used -sizeof(int[1]) in the right hand size to match the left, but I think it should always be the same. Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > #if defined __GNUC__ > # if !QEMU_GNUC_PREREQ(4, 4) > /* gcc versions before 4.4.x don't support gnu_printf, so use printf. */ > -- > MST > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h index 1a9eeb9..d2b05dd 100644 --- a/include/qemu/compiler.h +++ b/include/qemu/compiler.h @@ -88,6 +88,8 @@ #define QEMU_BUILD_BUG_ON(x) \ typedef char glue(qemu_build_bug_on__,__LINE__)[(x)?-1:1] __attribute__((unused)) +#define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(int[(x)?-1:1]) - sizeof(int)) + #if defined __GNUC__ # if !QEMU_GNUC_PREREQ(4, 4) /* gcc versions before 4.4.x don't support gnu_printf, so use printf. */
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 <mst@redhat.com> --- include/qemu/compiler.h | 2 ++ 1 file changed, 2 insertions(+)