[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 3/4] compiler: expression version of QEMU_BUILD_
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH 3/4] compiler: expression version of QEMU_BUILD_BUG_ON |
Date: |
Thu, 19 Jan 2017 11:29:49 +0000 |
User-agent: |
Mutt/1.7.1 (2016-10-04) |
* Michael S. Tsirkin (address@hidden) 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 <address@hidden>
> ---
> 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 <address@hidden>
> #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 / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH 0/4] virtio: ARRAY_SIZE fixups, Michael S. Tsirkin, 2017/01/18
- [Qemu-devel] [PATCH 1/4] virtio: fix up max size checks, Michael S. Tsirkin, 2017/01/18
- [Qemu-devel] [PATCH 2/4] compiler: drop ; after BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/18
- [Qemu-devel] [PATCH 3/4] compiler: expression version of QEMU_BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/18
- Re: [Qemu-devel] [PATCH 3/4] compiler: expression version of QEMU_BUILD_BUG_ON,
Dr. David Alan Gilbert <=
- [Qemu-devel] [PATCH 4/4] ARRAY_SIZE: check that argument is an array, Michael S. Tsirkin, 2017/01/18
- Re: [Qemu-devel] [PATCH 0/4] virtio: ARRAY_SIZE fixups, no-reply, 2017/01/18