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SubjectRe: [PATCH v4 00/13] Compiler Attributes
On Sat, Sep 8, 2018 at 2:25 PM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> The Compiler Attributes series is an effort to disentangle
> the include/linux/compiler*.h headers and bring them up to date.
>
> The main idea behind the series is to use feature checking macros
> (i.e. __has_attribute) instead of compiler version checks (e.g. GCC_VERSION),
> which are compiler-agnostic (so they can be shared, reducing the size
> of compiler-specific headers) and version-agnostic.
>
> Other related improvements have been performed in the headers as well,
> which on top of the use of __has_attribute it has amounted to a significant
> simplification of these headers (e.g. GCC_VERSION is now only guarding 4
> non-attribute macros).
>
> This series should also help the efforts to support compiling the kernel
> with clang and icc. A fair amount of documentation and comments have also
> been added, clarified or removed; and the headers are now more readable,
> which should help kernel developers in general.
>
> The series was triggered due to the move to gcc >= 4.6. In turn, this series
> has also triggered Sparse to gain the ability to recognize __has_attribute
> on its own.
>
> You can also fetch it from:
>
> https://github.com/ojeda/linux/tree/compiler-attributes-v4
>
> Enjoy!
>
> Cheers,
> Miguel
>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
> Cc: Eli Friedman <efriedma@codeaurora.org>
> Cc: Christopher Li <sparse@chrisli.org>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: Joe Perches <joe@perches.com>
> Cc: Dominique Martinet <asmadeus@codewreck.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: linux-sparse@vger.kernel.org
> Cc: linux-doc@vger.kernel.org
> Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
>
> v3 -> v4
>
> This time it is an important fix I found while doing randconfigs, plus
> the documentation sentence that Nick suggested and the MAINTAINERS file.
>
> Compile-tested for a while on (x86_64, gcc-7.3) on a few randconfs.
>
> New:
>
> * Add MAINTAINERS entry for the new file (compiler_attributes.h)
> so that we try to maintain that one as clean as possible.
> (if someone else wants to join, feel free!)
>
> Modified:
>
> * Fix inline macro
>
> __always_inline cannot be used in the inline macro,
> because people marking a function as __always_inline would
> expand to inline which in turn would expand back to __always_inline
> (under some configs), which would not be expanded again.
> Added a comment about this in the inline macro.
>
> Also added another comment about __always_inline in compiler_attributes.h
> to note that users expect to not have to write inline (as well as
> the attribute). We cannot simply remove "inline" there (which would
> solve the problem described above) because using the attribute is
> not enough for gcc. A function marked as always_inline seems to require
> to be marked as inline itself so that the attribute is applied:
>
> "warning: always_inline function might not be inlinable [-Wattributes]"
>
> From the gcc docs:
>
> "For functions declared inline, this attribute inlines the function
> independent of any restrictions that otherwise apply to inlining."
>
> See https://godbolt.org/z/LpzUPj for an example.
>
> From reviews:
>
> * Add sentence about feature-detection in Docs (Nick)
>
> Miguel Ojeda (13):
> Compiler Attributes: remove unused attributes
> Compiler Attributes: always use the extra-underscores syntax
> Compiler Attributes: remove unneeded tests
> Compiler Attributes: homogenize __must_be_array
> Compiler Attributes: naked was fixed in gcc 4.6
> Compiler Attributes: naked can be shared
> Compiler Attributes: remove unneeded sparse (__CHECKER__) tests
> Compiler Attributes: add missing SPDX ID in compiler_types.h
> Compiler Attributes: use feature checks instead of version checks
> Compiler Attributes: KENTRY used twice the "used" attribute
> Compiler Attributes: remove uses of __attribute__ from compiler.h
> Compiler Attributes: add Doc/process/programming-language.rst
> Compiler Attributes: Add MAINTAINERS entry
>
> Documentation/process/index.rst | 1 +
> .../process/programming-language.rst | 45 ++++
> MAINTAINERS | 5 +
> include/linux/compiler-clang.h | 5 -
> include/linux/compiler-gcc.h | 84 +-----
> include/linux/compiler-intel.h | 9 -
> include/linux/compiler.h | 19 +-
> include/linux/compiler_attributes.h | 244 ++++++++++++++++++
> include/linux/compiler_types.h | 105 ++------
> 9 files changed, 329 insertions(+), 188 deletions(-)
> create mode 100644 Documentation/process/programming-language.rst
> create mode 100644 include/linux/compiler_attributes.h
>
> --
> 2.17.1
>

For the ones I didn't already review:
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

--
Thanks,
~Nick Desaulniers

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