Re: [PATCH v4 8/9] bug.h: Add BUILD_BUG_ON_MSG & _BUILD_BUG_INTERNAL

Borislav Petkov
2012-10-30T17:17:55Z

On Sun, Oct 28, 2012 at 03:57:14PM -0500, danielfsantos@att.net wrote:
> Add BUILD_BUG_ON_MSG which behaves like BUILD_BUG_ON (with optimizations
> enabled), except that it allows you to specify the error message you
> want emitted as the third parameter. Under the hood, this relies on
> _BUILD_BUG_INTERNAL, which does the actual work and is pretty-much
> identical to BUILD_BUG_ON.
>
> Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
> ---
> include/linux/bug.h | 22 ++++++++++++++++++++++
> 1 files changed, 22 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/bug.h b/include/linux/bug.h
> index 6c38988..3bc1ddf 100644
> --- a/include/linux/bug.h
> +++ b/include/linux/bug.h
> @@ -16,6 +16,7 @@ struct pt_regs;
> #define BUILD_BUG_ON_NOT_POWER_OF_2(n)
> #define BUILD_BUG_ON_ZERO(e) (0)
> #define BUILD_BUG_ON_NULL(e) ((void*)0)
> +#define BUILD_BUG_ON_MSG(cond, msg) (0)
> #define BUILD_BUG_ON(condition) (0)
> #define BUILD_BUG() (0)
> #else /* __CHECKER__ */
> @@ -38,6 +39,27 @@ struct pt_regs;
> */
> #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
>
> +#define __BUILD_BUG_INTERNAL(condition, msg, line) \
> + do { \
> + extern void __build_bug_on_failed_ ## line \
> + (void) __compiletime_error(msg); \
> + __compiletime_error_fallback(condition); \
> + if (condition) \
> + __build_bug_on_failed_ ## line(); \
> + } while (0)
> +
> +#define _BUILD_BUG_INTERNAL(condition, msg, line) \
> + __BUILD_BUG_INTERNAL(condition, msg, line)

Stupid question:

can BUILD_BUG_ON and BUILD_BUG_ON_MSG both use __BUILD_BUG_INTERNAL?

In the BUILD_BUG_ON msg will be "BUILD_BUG_ON failed" and line empty.
Can that even work?

Thanks.

--
Regards/Gruss,
Boris.