[PATCH v5 00/15] Compiler Attributes

[Miguel Ojeda]

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.

Finally, the nonstring variable attribute series has been applied on top
of this one.

You can also fetch it from:

  https://github.com/ojeda/linux/tree/compiler-attributes-v5

Enjoy!

Cheers,
Miguel

Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx>
Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Cc: Michal Marek <michal.lkml@xxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>
Cc: Olof Johansson <olof@xxxxxxxx>
Cc: Konstantin Ryabitsev <konstantin@xxxxxxxxxxxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Paul Lawrence <paullawrence@xxxxxxxxxx>
Cc: Sandipan Das <sandipan@xxxxxxxxxxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Philippe Ombredanne <pombredanne@xxxxxxxx>
Cc: Paul Burton <paul.burton@xxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Willy Tarreau <w@xxxxxx>
Cc: Martin Sebor <msebor@xxxxxxxxx>
Cc: Christopher Li <sparse@xxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Dominique Martinet <asmadeus@xxxxxxxxxxxxx>
Cc: Stefan Agner <stefan@xxxxxxxx>
Cc: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-ext4@xxxxxxxxxxxxxxx
Cc: linux-sparse@xxxxxxxxxxxxxxx
Cc: linux-kbuild@xxxxxxxxxxxxxxx

v4 -> v5

  * Removed the 2 __naked patches, since Greg just applied them to master;
    and rebased on top of that. The only change in the range-diff is in
    "Compiler Attributes: always use the extra-underscores syntax" due
    to the move of __naked to compiler_types.h.

  * Applied the nonstring series on top of this one (last 4 patches).
    Rationale:
      - the nonstring series would anyway be modified again by this one
        (so it has been rebased after the general cleanup).
      - ext4's "local" nonstring was merged
      - easier to manage (and easier to see the end result)

    The first 2 patches of the last 4 add the warning back at W=1 and
    add the __nonstring attribute. The other two serve as an example
    of usage and as a cleanup.

  * Cc lists removed from each commit; using a single list in the cover letter;
    and a new, revised list of Cc (wider audience).

Miguel Ojeda (15):
  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: 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
  Compiler Attributes: add support for __nonstring (gcc >= 8)
  Compiler Attributes: enable -Wstringop-truncation on W=1 (gcc >= 8)
  Compiler Attributes: auxdisplay: panel: use __nonstring
  Compiler Attributes: ext4: remove local __nonstring definition

 Documentation/process/index.rst               |   1 +
 .../process/programming-language.rst          |  45 +++
 MAINTAINERS                                   |   5 +
 drivers/auxdisplay/panel.c                    |   7 +-
 fs/ext4/ext4.h                                |   9 -
 include/linux/compiler-clang.h                |   5 -
 include/linux/compiler-gcc.h                  |  70 +----
 include/linux/compiler-intel.h                |   9 -
 include/linux/compiler.h                      |  19 +-
 include/linux/compiler_attributes.h           | 258 ++++++++++++++++++
 include/linux/compiler_types.h                | 101 +------
 scripts/Makefile.extrawarn                    |   1 +
 12 files changed, 341 insertions(+), 189 deletions(-)
 create mode 100644 Documentation/process/programming-language.rst
 create mode 100644 include/linux/compiler_attributes.h

-- 
2.17.1