On Tue, Oct 27, 2020 at 10:42 AM Nathan Chancellor <natechancellor@xxxxxxxxx> wrote: > > On Mon, Oct 26, 2020 at 11:03:13PM +0100, Arnd Bergmann wrote: > > From: Arnd Bergmann <arnd@xxxxxxxx> > > > > This warning behaves differently depending on the architecture > > and compiler. Using x86 gcc, we get no output at all because > > gcc knows the architecture can handle unaligned accesses. > > > > Using x86 clang, or gcc on an architecture that needs to > > manually deal with unaligned accesses, the build log is > > completely flooded with these warnings, as they are commonly > > invoked by inline functions of networking headers, e.g. > > > > include/linux/skbuff.h:1426:26: warning: cast increases required alignment of target type [-Wcast-align] > > > > The compiler is correct to point this out, as we are dealing > > with undefined behavior that does cause problems in practice, > > but there is also no good way to rewrite the code in commonly > > included headers to a safer method. > > > > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> > > Always sad to see a warning move further down the list but noisy headers > are rough to deal with. This seems okay. > > Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > > > --- > > scripts/Makefile.extrawarn | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn > > index 95e4cdb94fe9..6baee1200615 100644 > > --- a/scripts/Makefile.extrawarn > > +++ b/scripts/Makefile.extrawarn > > @@ -60,7 +60,6 @@ endif > > # > > ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),) > > > > -KBUILD_CFLAGS += -Wcast-align > > KBUILD_CFLAGS += -Wdisabled-optimization > > KBUILD_CFLAGS += -Wnested-externs > > KBUILD_CFLAGS += -Wshadow > > @@ -80,6 +79,7 @@ endif > > ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),) > > > > KBUILD_CFLAGS += -Wbad-function-cast > > +KBUILD_CFLAGS += -Wcast-align > > KBUILD_CFLAGS += -Wcast-qual > > KBUILD_CFLAGS += -Wconversion > > KBUILD_CFLAGS += -Wpacked > > -- > > 2.27.0 > > Applied to linux-kbuild. Thanks. But, I think people already tend to ignore W=2 warnings. -- Best Regards Masahiro Yamada
