From: Peter Zijlstra > Sent: 27 October 2020 10:33 > > On Tue, Oct 27, 2020 at 09:33:32AM +0100, Arnd Bergmann wrote: > > On Tue, Oct 27, 2020 at 8:47 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > On Mon, Oct 26, 2020 at 02:03:06PM -0400, Waiman Long wrote: > > > > On 10/26/20 12:57 PM, Arnd Bergmann wrote: > > > > Yes, it shouldn't really matter if the value is defined as int or u32. > > > > However, the only caveat that I see is queued_spin_lock_slowpath() is > > > > expecting a u32 argument. Maybe you should cast it back to (u32) when > > > > calling it. > > > > > > No, we're not going to confuse the code. That stuff is hard enough as it > > > is. This warning is garbage and just needs to stay off. > > > > Ok, so the question then becomes: should we drop -Wpointer-sign from > > W=2 and move it to W=3, or instead disable it locally. I could add > > __diag_ignore(GCC, 4, "-Wpointer-sign") in the couple of header files > > that produce this kind of warning if there is a general feeling that it > > still helps to have this for drivers. > > What is an actual geniune bug that this warning helps find? > > Note that the kernel relies on -fno-strict-overflow to get rid of the > signed UB that is otherwise present in C. > > If you add that __diag_ignore() it should go in atomic.h I suppose, > because all of atomic hard relies on this, and then the question becomes > how much code is left that doesn't include that header and consequently > doesn't ignore that warning. > > So, is it useful to begin with in finding actual problems? and given we > have to annotate away a bucket-load, how much coverage will there remain > if we squish the known false-positives? Especially since adding casts just makes the code harder to read and can easily hide real bugs. FWIW you might want to try -Wwrite-strings. That ought to be fixable by sprinkling 'const. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
