Messages in this thread | | | Date | Tue, 15 Sep 2015 07:22:02 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC][PATCH 5/5] abs(): Provide build error on passing 64bit value to abs() |
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* John Stultz <john.stultz@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 <akpm@linux-foundation.org> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> > Cc: Michal Nazarewicz <mina86@mina86.com> > Signed-off-by: John Stultz <john.stultz@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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