Messages in this thread Patch in this message | | | From | John Stultz <> | Subject | [RFC][PATCH 5/5] abs(): Provide build error on passing 64bit value to abs() | Date | Mon, 14 Sep 2015 18:05:24 -0700 |
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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; \ -- 1.9.1
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