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During a patch discussion, Linus brought up the option of changing the C standard version from gnu89 to gnu99, which allows using variable declaration inside of a for() loop. While the C99, C11 and later standards introduce many other features, most of these are already available in gnu89 as GNU extensions as well. An earlier attempt to do this when gcc-5 started defaulting to -std=gnu11 failed because at the time that caused warnings about designated initializers with older compilers. Now that gcc-5.1 is the minimum compiler version used for building kernels, that is no longer a concern. Similarly, the behavior of 'inline' functions changes between gnu89 using gnu_inline behavior and gnu11 using standard c99+ behavior, but this was taken care of by defining 'inline' to include __attribute__((gnu_inline)) in order to allow building with clang a while ago. Nathan Chancellor reported a new -Wdeclaration-after-statement warning that appears in a system header on arm, this still needs a workaround. The differences between gnu99, gnu11, gnu1x and gnu17 are fairly minimal and mainly impact warnings at the -Wpedantic level that the kernel never enables. Between these, gnu11 is the newest version that is supported by all supported compiler versions, though it is only the default on gcc-5, while all other supported versions of gcc or clang default to gnu1x/gnu17. Link: https://lore.kernel.org/lkml/CAHk-=wiyCH7xeHcmiFJ-YgXUy2Jaj7pnkdKpcovt8fYbVFW3TA@mail.gmail.com/ Link: https://github.com/ClangBuiltLinux/linux/issues/1603 Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Marco Elver <elver@google.com> Acked-by: Jani Nikula <jani.nikula@intel.com> Acked-by: David Sterba <dsterba@suse.com> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Reviewed-by: Alex Shi <alexs@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> |
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| doc-guide | ||
| kernel-hacking | ||
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| process | ||
| riscv | ||
| disclaimer-ita.rst | ||
| index.rst | ||