On Sat, Sep 8, 2018 at 2:25 PM Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx> 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@xxxxxxx> > Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> > Cc: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx> > Cc: Eli Friedman <efriedma@xxxxxxxxxxxxxx> > Cc: Christopher Li <sparse@xxxxxxxxxxx> > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > Cc: Arnd Bergmann <arnd@xxxxxxxx> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> > Cc: Joe Perches <joe@xxxxxxxxxxx> > Cc: Dominique Martinet <asmadeus@xxxxxxxxxxxxx> > Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Cc: linux-sparse@xxxxxxxxxxxxxxx > Cc: linux-doc@xxxxxxxxxxxxxxx > Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx> > > 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@xxxxxxxxxx> -- Thanks, ~Nick Desaulniers
