From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Date: Tue, 23 Apr 2013 10:52:33 -0700 > On Tue, Apr 23, 2013 at 10:37 AM, David Miller <davem@xxxxxxxxxxxxx> wrote: >> >> I just want to mention that this is dangerous in different ways, we >> just recently got a patch in the networking that removed such a cast. >> The problem is when the cast narrows, f.e.: >> >> ~(u8)0 >> >> doesn't do what you think it does. That doesn't evaluate to 0xff. > > Yeah, sparse will get that right, but won't warn about it even with my > patch. The normal "all arithmetic is done in *at*least* 'int'" will > always kick any C expression like that up to 'int' before the binary > not op is done. So in your example, the implicit cast is widening the > value *before* the binary not, not after. If you're not bored, and could add a check for that kind of narrowing situation, I'd really appreciate it. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
