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 <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: "Steven Rostedt (Red Hat)" <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Masami Hiramatsu <[email protected]> Cc: Michal Nazarewicz <[email protected]> Signed-off-by: John Stultz <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
