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Makefile.extrawarn: Move -Wunaligned-access to W=1

PATCH In review Nathan Chancellor 2 participants 2 messages Feb 14, 2022 – Feb 17, 2022 Stable branch

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Nathan Chancellor

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PATCH 1/1 Makefile.extrawarn: Move -Wunaligned-access to W=1

commit 1cf5f151d25fcca94689efd91afa0253621fb33a upstream.

-Wunaligned-access is a new warning in clang that is default enabled for arm and arm64 under certain circumstances within the clang frontend (see LLVM commit below). On v5.17-rc2, an ARCH=arm allmodconfig build shows 1284 total/70 unique instances of this warning (most of the instances are in header files), which is quite noisy.

To keep a normal build green through CONFIG_WERROR, only show this warning with W=1, which will allow automated build systems to catch new instances of the warning so that the total number can be driven down to zero eventually since catching unaligned accesses at compile time would be generally useful.

Cc [email protected]
Link https://github.com/llvm/llvm-project/commit/35737df4dcd28534bd3090157c224c19b501278a
Link https://github.com/ClangBuiltLinux/linux/issues/1569
Link https://github.com/ClangBuiltLinux/linux/issues/1576
Signed-off-by Nathan Chancellor <[email protected]>
Reviewed-by Nick Desaulniers <[email protected]>
Signed-off-by Masahiro Yamada <[email protected]>
[nathan: Fix conflict due to lack of afe956c577b2d]
Signed-off-by Nathan Chancellor <[email protected]>

---

I am not sure how many people are using ToT clang with ARCH=arm on stable but given how noisy this warning can be, I think it is worth applying this to all applicable stable branches.

This applies to 4.9 through 5.4 with 'patch -Np1'.

 scripts/Makefile.extrawarn | 1 +
 1 file changed, 1 insertion(+)
scripts/Makefile.extrawarn +1 -0
index ca08f2fe7c34..854e2ba9daa2 100644
@@ -49,6 +49,7 @@ KBUILD_CFLAGS += -Wno-format
 KBUILD_CFLAGS += -Wno-sign-compare
 KBUILD_CFLAGS += -Wno-format-zero-length
 KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
+KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
 endif
 
 endif

base-commit: 52871671099d1bb3fca5ed076029e4b937bfc053

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2.35.1
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#1 lore raw
Quoted 25 lines · Nathan Chancellor

commit 1cf5f151d25fcca94689efd91afa0253621fb33a upstream.

-Wunaligned-access is a new warning in clang that is default enabled for arm and arm64 under certain circumstances within the clang frontend (see LLVM commit below). On v5.17-rc2, an ARCH=arm allmodconfig build shows 1284 total/70 unique instances of this warning (most of the instances are in header files), which is quite noisy.

To keep a normal build green through CONFIG_WERROR, only show this warning with W=1, which will allow automated build systems to catch new instances of the warning so that the total number can be driven down to zero eventually since catching unaligned accesses at compile time would be generally useful.

Cc [email protected]
Link https://github.com/llvm/llvm-project/commit/35737df4dcd28534bd3090157c224c19b501278a
Link https://github.com/ClangBuiltLinux/linux/issues/1569
Link https://github.com/ClangBuiltLinux/linux/issues/1576
Signed-off-by Nathan Chancellor <[email protected]>
Reviewed-by Nick Desaulniers <[email protected]>
Signed-off-by Masahiro Yamada <[email protected]>
[nathan: Fix conflict due to lack of afe956c577b2d]
Signed-off-by Nathan Chancellor <[email protected]>

---

Quoted 8 lines

I am not sure how many people are using ToT clang with ARCH=arm on stable but given how noisy this warning can be, I think it is worth applying this to all applicable stable branches.

This applies to 4.9 through 5.4 with 'patch -Np1'.

 scripts/Makefile.extrawarn | 1 +
 1 file changed, 1 insertion(+)

Now queued up, thanks.

greg k-h