* John Stultz <john.stu...@linaro.org> wrote:
> As noted in the comment above abs():
> "abs() should not be used for 64-bit types (s64, u64, long long)
> - use abs64() for those."
>
> Unfortunately, its quite easy to pass 64-bit values to abs()
> accidentally, and the compiler provides no warning when the
> returned value is erroniously capped at 32-bits.
>
> So this patch tries to make it easier to detect when 64-bit
> values are passed to abs() by generating a build error.
>
> Obviously, since this causes build errors, this patch is last
> in the series, and I tried to fix up all of the issues I ran
> into in my build testing. But there are likely still some out
> there.
>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: Ingo Molnar <mi...@kernel.org>
> Cc: "Steven Rostedt (Red Hat)" <rost...@goodmis.org>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
> Cc: Michal Nazarewicz <min...@mina86.com>
> Signed-off-by: John Stultz <john.stu...@linaro.org>
> ---
> include/linux/kernel.h | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 5582410..6f01151 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -208,6 +208,9 @@ extern int _cond_resched(void);
> */
> #define abs(x) ({ \
> long ret; \
> + compiletime_assert( \
> + !(sizeof(typeof(x)) > sizeof(long)), \
> + "abs() should not be used for 64-bit types - use
> abs64()");\
> if (sizeof(x) == sizeof(long)) { \
> long __x = (x); \
> ret = (__x < 0) ? -__x : __x; \
I think this should be a compiletime_warning() - that will be visible enough.
Thanks,
Ingo
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