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Build with -Werror=unused-command-line-argument #1587

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nathanchance opened this issue Feb 14, 2022 · 3 comments
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Build with -Werror=unused-command-line-argument #1587

nathanchance opened this issue Feb 14, 2022 · 3 comments
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enhancement New feature or request [FIXED][LINUX] 6.3 This bug was fixed in Linux 6.3

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@nathanchance
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Similar to what was done in commit 589834b3a009 ("kbuild: Add -Werror=unknown-warning-option to CLANG_FLAGS") and 0664684e1ebd ("kbuild: Add -Werror=ignored-optimization-argument to CLANG_FLAGS"), I would like to turn -Wunused-command-line-argument into an error because flags that trigger this warning, such as -mno-branch-likely, will break cc-option.cc-option failures cause unnecessary noise due to the presence of warnings that would normally be hidden. By upgrading this option to an error, the error will be visible before the cc-option failure.

Currently, this is blocked on resolving #1315.
@nathanchance nathanchance added the enhancement New feature or request label Feb 14, 2022
intel-lab-lkp pushed a commit to intel-lab-lkp/linux that referenced this issue May 16, 2022
@nickdesaulniers @intel-lab-lkp
ARM: pass -march= only to compiler
6da9810 
When both -march= and -Wa,-march= are specified for assembler or
assembler-with-cpp sources, GCC and Clang will prefer the -Wa,-march=
value but Clang will warn that -march= is unused.

warning: argument unused during compilation: '-march=armv6k'
[-Wunused-command-line-argument]

This is the top group of warnings we observe when using clang to
assemble the kernel via `ARCH=arm make LLVM=1`.

Split the arch-y make variable into two, so that -march= flags only get
passed to the compiler, not the assembler. -D flags are added to
KBUILD_CPPFLAGS which is used for both C and assembler-with-cpp sources.

Link: ClangBuiltLinux#1315
Link: ClangBuiltLinux#1587
Link: https://lore.kernel.org/llvm/628249e8.1c69fb81.d20fd.02ea@mx.google.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
intel-lab-lkp pushed a commit to intel-lab-lkp/linux that referenced this issue Oct 17, 2022
@nickdesaulniers @intel-lab-lkp
ARM: pass -march= only to compiler
b676fe2 
When both -march= and -Wa,-march= are specified for assembler or
assembler-with-cpp sources, GCC and Clang will prefer the -Wa,-march=
value but Clang will warn that -march= is unused.

warning: argument unused during compilation: '-march=armv6k'
[-Wunused-command-line-argument]

This is the top group of warnings we observe when using clang to
assemble the kernel via `ARCH=arm make LLVM=1`.

Split the arch-y make variable into two, so that -march= flags only get
passed to the compiler, not the assembler. -D flags are added to
KBUILD_CPPFLAGS which is used for both C and assembler-with-cpp sources.

Clang is trying to warn that it doesn't support different values for
-march= and -Wa,-march= (like GCC does, but the kernel doesn't need this)
though the value of the preprocessor define __thumb2__ is based on
-march=. Make sure to re-set __thumb2__ via -D flag for assembler
sources now that we're no longer passing -march= to the assembler. Set
it to a different value than the preprocessor would for -march= in case
-march= gets accidentally re-added to KBUILD_AFLAGS in the future.
Thanks to Ard and Nathan for this suggestion.

Link: ClangBuiltLinux#1315
Link: ClangBuiltLinux#1587
Link: llvm/llvm-project#55656
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
jonhunter pushed a commit to jonhunter/linux that referenced this issue Nov 8, 2022
@nickdesaulniers
ARM: 9265/1: pass -march= only to compiler
59247fe 
When both -march= and -Wa,-march= are specified for assembler or
assembler-with-cpp sources, GCC and Clang will prefer the -Wa,-march=
value but Clang will warn that -march= is unused.

warning: argument unused during compilation: '-march=armv6k'
[-Wunused-command-line-argument]

This is the top group of warnings we observe when using clang to
assemble the kernel via `ARCH=arm make LLVM=1`.

Split the arch-y make variable into two, so that -march= flags only get
passed to the compiler, not the assembler. -D flags are added to
KBUILD_CPPFLAGS which is used for both C and assembler-with-cpp sources.

Clang is trying to warn that it doesn't support different values for
-march= and -Wa,-march= (like GCC does, but the kernel doesn't need this)
though the value of the preprocessor define __thumb2__ is based on
-march=. Make sure to re-set __thumb2__ via -D flag for assembler
sources now that we're no longer passing -march= to the assembler. Set
it to a different value than the preprocessor would for -march= in case
-march= gets accidentally re-added to KBUILD_AFLAGS in the future.
Thanks to Ard and Nathan for this suggestion.

Link: ClangBuiltLinux#1315
Link: ClangBuiltLinux#1587
Link: llvm/llvm-project#55656

Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
jonhunter pushed a commit to jonhunter/linux that referenced this issue Nov 9, 2022
@nickdesaulniers
ARM: 9265/1: pass -march= only to compiler
1d2e9b6 
When both -march= and -Wa,-march= are specified for assembler or
assembler-with-cpp sources, GCC and Clang will prefer the -Wa,-march=
value but Clang will warn that -march= is unused.

warning: argument unused during compilation: '-march=armv6k'
[-Wunused-command-line-argument]

This is the top group of warnings we observe when using clang to
assemble the kernel via `ARCH=arm make LLVM=1`.

Split the arch-y make variable into two, so that -march= flags only get
passed to the compiler, not the assembler. -D flags are added to
KBUILD_CPPFLAGS which is used for both C and assembler-with-cpp sources.

Clang is trying to warn that it doesn't support different values for
-march= and -Wa,-march= (like GCC does, but the kernel doesn't need this)
though the value of the preprocessor define __thumb2__ is based on
-march=. Make sure to re-set __thumb2__ via -D flag for assembler
sources now that we're no longer passing -march= to the assembler. Set
it to a different value than the preprocessor would for -march= in case
-march= gets accidentally re-added to KBUILD_AFLAGS in the future.
Thanks to Ard and Nathan for this suggestion.

Link: ClangBuiltLinux#1315
Link: ClangBuiltLinux#1587
Link: llvm/llvm-project#55656

Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
@nathanchance
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Patch submitted: https://lore.kernel.org/20221228-drop-qunused-arguments-v1-13-658cbc8fc592@kernel.org/

@nathanchance nathanchance self-assigned this Jan 4, 2023
@nathanchance nathanchance added the [PATCH] Submitted A patch has been submitted for review label Jan 4, 2023
@nathanchance
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v2: https://lore.kernel.org/20221228-drop-qunused-arguments-v2-13-9adbddd20d86@kernel.org/

intel-lab-lkp pushed a commit to intel-lab-lkp/linux that referenced this issue Jan 23, 2023
@nathanchance @masahir0y
kbuild: Turn a couple more of clang's unused option warnings into errors
0afbf7f 
Currently, these warnings are hidden with -Qunused-arguments in
KBUILD_CPPFLAGS. Once that option is removed, these warnings should be
turned into hard errors to make unconditionally added but unsupported
flags for the current compilation mode or target obvious due to a failed
build; otherwise, the warnings might just be ignored if the build log is
not checked.

Link: ClangBuiltLinux#1587
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
sirlucjan pushed a commit to CachyOS/linux that referenced this issue Feb 17, 2023
@nathanchance @sirlucjan
kbuild: Turn a couple more of clang's unused option warnings into errors
1810c70 
Currently, these warnings are hidden with -Qunused-arguments in
KBUILD_CPPFLAGS. Once that option is removed, these warnings should be
turned into hard errors to make unconditionally added but unsupported
flags for the current compilation mode or target obvious due to a failed
build; otherwise, the warnings might just be ignored if the build log is
not checked.

Link: ClangBuiltLinux#1587
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
@nathanchance
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Now in mainline: https://git.kernel.org/linus/db1547c56886742283d7566c872f89cbad76a14c

@nathanchance nathanchance added [FIXED][LINUX] 6.3 This bug was fixed in Linux 6.3 and removed [PATCH] Submitted A patch has been submitted for review labels Feb 27, 2023
thanasxda pushed a commit to thanasxda/clrxt-x86 that referenced this issue Mar 2, 2023
@nathanchance
kbuild: Turn a couple more of clang's unused option warnings into errors
29f7ad8 
Currently, these warnings are hidden with -Qunused-arguments in
KBUILD_CPPFLAGS. Once that option is removed, these warnings should be
turned into hard errors to make unconditionally added but unsupported
flags for the current compilation mode or target obvious due to a failed
build; otherwise, the warnings might just be ignored if the build log is
not checked.

Link: ClangBuiltLinux/linux#1587
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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enhancement New feature or request [FIXED][LINUX] 6.3 This bug was fixed in Linux 6.3
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