On Tue, May 5, 2020 at 4:08 PM Andy Shevchenko <andy.shevche...@gmail.com> wrote: > On Tue, May 5, 2020 at 4:58 PM Arnd Bergmann <a...@arndb.de> wrote: > > Clang normally does not warn about certain issues in inline functions when > > it only happens in an eliminated code path. However if something else > > goes wrong, it does tend to complain about the definition of hweight_long() > > on 32-bit targets: > > Shouldn't it be fixed in CLang? > > > include/linux/bitops.h:75:41: error: shift count >= width of type > > [-Werror,-Wshift-count-overflow] > > return sizeof(w) == 4 ? hweight32(w) : hweight64(w); > > ^~~~~~~~~~~~ > > sizeof(w) is compile-time constant. It can easily drop the second part > without even looking at it. > > > Adding an explicit cast to __u64 avoids that warning and makes it easier > > to read other output. > > Looks like papering over the real issue.
I'm not sure if there is anything to be done about it in clang, since it always does syntactic analysis before dead-code elimination by design. It is a bit odd though that it only prints the warning sometimes, but I suspect this is also something that works as designed. Maybe someone on the clang-built-linux list knows more about the background. Arnd