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| author | Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> | 2018-09-03 18:32:11 +0200 |
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| committer | Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> | 2018-09-30 20:14:04 +0200 |
| commit | 303d22c5fc37cebe2bd0b3c15ac3db6950db60c6 (patch) | |
| tree | 72dd91668170a2683d0f25d91967c1b65393bd92 | |
| parent | e04462fb82f8dd98288c0e7ab1eec79c92537d25 (diff) | |
| download | lwn-303d22c5fc37cebe2bd0b3c15ac3db6950db60c6.tar.gz lwn-303d22c5fc37cebe2bd0b3c15ac3db6950db60c6.zip | |
Compiler Attributes: add Doc/process/programming-language.rst
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # on top of v4.19-rc5, clang 7
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
| -rw-r--r-- | Documentation/process/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/process/programming-language.rst | 45 |
2 files changed, 46 insertions, 0 deletions
diff --git a/Documentation/process/index.rst b/Documentation/process/index.rst index 9ae3e317bddf..00558b6d2649 100644 --- a/Documentation/process/index.rst +++ b/Documentation/process/index.rst @@ -23,6 +23,7 @@ Below are the essential guides that every developer should read. code-of-conduct development-process submitting-patches + programming-language coding-style maintainer-pgp-guide email-clients diff --git a/Documentation/process/programming-language.rst b/Documentation/process/programming-language.rst new file mode 100644 index 000000000000..e5f5f065dc24 --- /dev/null +++ b/Documentation/process/programming-language.rst @@ -0,0 +1,45 @@ +.. _programming_language: + +Programming Language +==================== + +The kernel is written in the C programming language [c-language]_. +More precisely, the kernel is typically compiled with ``gcc`` [gcc]_ +under ``-std=gnu89`` [gcc-c-dialect-options]_: the GNU dialect of ISO C90 +(including some C99 features). + +This dialect contains many extensions to the language [gnu-extensions]_, +and many of them are used within the kernel as a matter of course. + +There is some support for compiling the kernel with ``clang`` [clang]_ +and ``icc`` [icc]_ for several of the architectures, although at the time +of writing it is not completed, requiring third-party patches. + +Attributes +---------- + +One of the common extensions used throughout the kernel are attributes +[gcc-attribute-syntax]_. Attributes allow to introduce +implementation-defined semantics to language entities (like variables, +functions or types) without having to make significant syntactic changes +to the language (e.g. adding a new keyword) [n2049]_. + +In some cases, attributes are optional (i.e. a compiler not supporting them +should still produce proper code, even if it is slower or does not perform +as many compile-time checks/diagnostics). + +The kernel defines pseudo-keywords (e.g. ``__pure``) instead of using +directly the GNU attribute syntax (e.g. ``__attribute__((__pure__))``) +in order to feature detect which ones can be used and/or to shorten the code. + +Please refer to ``include/linux/compiler_attributes.h`` for more information. + +.. [c-language] http://www.open-std.org/jtc1/sc22/wg14/www/standards +.. [gcc] https://gcc.gnu.org +.. [clang] https://clang.llvm.org +.. [icc] https://software.intel.com/en-us/c-compilers +.. [gcc-c-dialect-options] https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html +.. [gnu-extensions] https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html +.. [gcc-attribute-syntax] https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html +.. [n2049] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2049.pdf + |