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61 lines
2.7 KiB
Diff
61 lines
2.7 KiB
Diff
From b810c8e719ea082e47c7a8f7cf878bc84fa2455d Mon Sep 17 00:00:00 2001
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From: Arnd Bergmann <arnd@arndb.de>
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Date: Tue, 8 Mar 2022 22:56:14 +0100
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Subject: [PATCH 2/3] Kbuild: move to -std=gnu11
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During a patch discussion, Linus brought up the option of changing
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the C standard version from gnu89 to gnu99, which allows using variable
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declaration inside of a for() loop. While the C99, C11 and later standards
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introduce many other features, most of these are already available in
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gnu89 as GNU extensions as well.
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An earlier attempt to do this when gcc-5 started defaulting to
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-std=gnu11 failed because at the time that caused warnings about
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designated initializers with older compilers. Now that gcc-5.1 is
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the minimum compiler version used for building kernels, that is no
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longer a concern. Similarly, the behavior of 'inline' functions changes
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between gnu89 using gnu_inline behavior and gnu11 using standard c99+
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behavior, but this was taken care of by defining 'inline' to include
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__attribute__((gnu_inline)) in order to allow building with clang a
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while ago.
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Nathan Chancellor reported a new -Wdeclaration-after-statement
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warning that appears in a system header on arm, this still needs a
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workaround.
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The differences between gnu99, gnu11, gnu1x and gnu17 are fairly
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minimal and mainly impact warnings at the -Wpedantic level that the
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kernel never enables. Between these, gnu11 is the newest version
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that is supported by all supported compiler versions, though it is
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only the default on gcc-5, while all other supported versions of
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gcc or clang default to gnu1x/gnu17.
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Link: https://lore.kernel.org/lkml/CAHk-=wiyCH7xeHcmiFJ-YgXUy2Jaj7pnkdKpcovt8fYbVFW3TA@mail.gmail.com/
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Link: https://github.com/ClangBuiltLinux/linux/issues/1603
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Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
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Acked-by: Marco Elver <elver@google.com>
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Acked-by: Jani Nikula <jani.nikula@intel.com>
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Acked-by: David Sterba <dsterba@suse.com>
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Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
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Reviewed-by: Alex Shi <alexs@kernel.org>
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Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
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Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
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Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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Reviewed-by: Nathan Chancellor <nathan@kernel.org>
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Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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---
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Makefile | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/Makefile
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+++ b/Makefile
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@@ -500,7 +500,7 @@ KBUILD_CFLAGS := -Wall -Wundef -Werror
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-fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \
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-Werror=implicit-function-declaration -Werror=implicit-int \
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-Werror=return-type -Wno-format-security \
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- -std=gnu89
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+ -std=gnu11
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KBUILD_CPPFLAGS := -D__KERNEL__
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KBUILD_AFLAGS_KERNEL :=
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KBUILD_CFLAGS_KERNEL :=
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