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Makefile.extrawarn: move -Wcast-align to W=3 

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@arndb.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Arnd Bergmann 2020-10-26 23:03:13 +01:00 committed by Masahiro Yamada
parent 418baf2c28
commit 095fbca0a9
1 changed files with 1 additions and 1 deletions
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2
scripts/Makefile.extrawarn
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@ -60,7 +60,6 @@ endif
# #
ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),) ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
KBUILD_CFLAGS += -Wcast-align
KBUILD_CFLAGS += -Wdisabled-optimization KBUILD_CFLAGS += -Wdisabled-optimization
KBUILD_CFLAGS += -Wnested-externs KBUILD_CFLAGS += -Wnested-externs
KBUILD_CFLAGS += -Wshadow KBUILD_CFLAGS += -Wshadow
@ -80,6 +79,7 @@ endif
ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),) ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
KBUILD_CFLAGS += -Wbad-function-cast KBUILD_CFLAGS += -Wbad-function-cast
KBUILD_CFLAGS += -Wcast-align
KBUILD_CFLAGS += -Wcast-qual KBUILD_CFLAGS += -Wcast-qual
KBUILD_CFLAGS += -Wconversion KBUILD_CFLAGS += -Wconversion
KBUILD_CFLAGS += -Wpacked KBUILD_CFLAGS += -Wpacked