On Wed, 20 May 2015, Oleg Nesterov wrote: > On 05/19, Nicholas Mc Guire wrote: > > > > I assumed it would not matter but did not see a simple way of getting it > > type clean with unsigned either mainly due to the atomic_t being int and > > val in update_fast_ctr() being passed as -1. > > Perhaps clear_fast_ctr() should have a comment to explain why it returns > "int"... even if "unsigned" should work too. > Might not be into c99 standard far enough but from reviewing 6.5/J.2 I do not see this argument here.
The "well defined modulo 2**n" behavior for unsigned int can be found stated in a few places - but not in the c99 standard for arithmetic overflow. The "well defined overflow behavior" as far as I understand c99, *only* applies to left shift operations when overflowing - see 6.5.7 " Bitwise shift operators" -> Semantics -> 4) - further for the counter problem this well defined behavior is of little help as the sum would be wrong in both cases. I still do not see the point in the implicit/automatic type conversion here and why that should be an advantage - could somone point me to the right c99 clauses ? thx! hofrat -- 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/
