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Re: [Qemu-devel] [PATCH v3 3/4] compiler: expression version of QEMU_BUI
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v3 3/4] compiler: expression version of QEMU_BUILD_BUG_ON |
Date: |
Thu, 19 Jan 2017 15:28:55 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 |
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 <address@hidden>
> ---
> include/qemu/compiler.h | 3 +++
> 1 file changed, 3 insertions(+)
Reviewed-by: Eric Blake <address@hidden>
>
> 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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Re: [Qemu-devel] [PATCH v3 0/4] ARRAY_SIZE fixups, Markus Armbruster, 2017/01/20
Re: [Qemu-devel] [PATCH v3 0/4] ARRAY_SIZE fixups, no-reply, 2017/01/20
Re: [Qemu-devel] [PATCH v3 0/4] ARRAY_SIZE fixups, no-reply, 2017/01/20