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Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUI
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON |
Date: |
Thu, 19 Jan 2017 09:12:49 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) |
"Michael S. Tsirkin" <address@hidden> writes:
> 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.
Following Linux's example makes sense, but I can't help but wonder
whether we need both QEMU_BUILD_BUG_ON_ZERO() and QEMU_BUILD_BUG_ON().
> 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 2882470..f4cf13b 100644
> --- a/include/qemu/compiler.h
> +++ b/include/qemu/compiler.h
> @@ -89,6 +89,8 @@
> 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. */
More so since your QEMU_BUILD_BUG_ON_ZERO seems easier to understand: no
token pasting.
Anyway,
Reviewed-by: Markus Armbruster <address@hidden>
[Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/18
- Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON,
Markus Armbruster <=
- Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON, Paolo Bonzini, 2017/01/19
- Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON, Markus Armbruster, 2017/01/19
- Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/19
- Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON, Eric Blake, 2017/01/19
- Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/19
- Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON, Markus Armbruster, 2017/01/20
- Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/20
Re: [Qemu-devel] [PATCH v2 3/4] compiler: expression version of QEMU_BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/19
[Qemu-devel] [PATCH v2 4/4] ARRAY_SIZE: check that argument is an array, Michael S. Tsirkin, 2017/01/18