On Sat, Dec 10, 2016 at 02:14:00AM +0000, Al Viro wrote: > On Wed, Dec 07, 2016 at 03:33:42PM +0100, Luc Van Oostenryck wrote: > > But what is really done currently is something like: > > x = x + (typeof(x)) a; > > In other words, the left-hand side is casted to the same type as the > > rhs and the operation is always done with this type, neglecting the > > usual conversions and thus forcing the operation to always be done > > with the rhs type, here 'int' instead of 'long'. > > Addition is a bad example, actually - your variant (promotions + operaton + > cast down to the first argument due to assignment) will yield the same value. > It's division where the real trouble happens - > unsigned n1 = 1, n2 = 1; > long v = -1; > n1 /= v; > n2 /= (unsigned)v; > > should yield n1 == ~0U, n2 == 0. And yes, the current logics in sparse > does not distinguish between those. So ACK on the fix, but you want > a better testcase. Absolutely. In fact, I found the problem when a was a double and I saw that the addition was still done with a 32bit wide operation. I used this example because there is too much problems with floating-point operations. I'll reuse your example, which is more 'dramatic' that mine. Thanks for the review. -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
