1.. _programming_language: 2 3Programming Language 4==================== 5 6The kernel is written in the C programming language [c-language]_. 7More precisely, the kernel is typically compiled with ``gcc`` [gcc]_ 8under ``-std=gnu11`` [gcc-c-dialect-options]_: the GNU dialect of ISO C11. 9``clang`` [clang]_ is also supported, see docs on 10:ref:`Building Linux with Clang/LLVM <kbuild_llvm>`. 11 12This dialect contains many extensions to the language [gnu-extensions]_, 13and many of them are used within the kernel as a matter of course. 14 15Attributes 16---------- 17 18One of the common extensions used throughout the kernel are attributes 19[gcc-attribute-syntax]_. Attributes allow to introduce 20implementation-defined semantics to language entities (like variables, 21functions or types) without having to make significant syntactic changes 22to the language (e.g. adding a new keyword) [n2049]_. 23 24In some cases, attributes are optional (i.e. a compiler not supporting them 25should still produce proper code, even if it is slower or does not perform 26as many compile-time checks/diagnostics). 27 28The kernel defines pseudo-keywords (e.g. ``__pure``) instead of using 29directly the GNU attribute syntax (e.g. ``__attribute__((__pure__))``) 30in order to feature detect which ones can be used and/or to shorten the code. 31 32Please refer to ``include/linux/compiler_attributes.h`` for more information. 33 34Rust 35---- 36 37The kernel has experimental support for the Rust programming language 38[rust-language]_ under ``CONFIG_RUST``. It is compiled with ``rustc`` [rustc]_ 39under ``--edition=2021`` [rust-editions]_. Editions are a way to introduce 40small changes to the language that are not backwards compatible. 41 42On top of that, some unstable features [rust-unstable-features]_ are used in 43the kernel. Unstable features may change in the future, thus it is an important 44goal to reach a point where only stable features are used. 45 46Please refer to Documentation/rust/index.rst for more information. 47 48.. [c-language] http://www.open-std.org/jtc1/sc22/wg14/www/standards 49.. [gcc] https://gcc.gnu.org 50.. [clang] https://clang.llvm.org 51.. [gcc-c-dialect-options] https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html 52.. [gnu-extensions] https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html 53.. [gcc-attribute-syntax] https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html 54.. [n2049] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2049.pdf 55.. [rust-language] https://www.rust-lang.org 56.. [rustc] https://doc.rust-lang.org/rustc/ 57.. [rust-editions] https://doc.rust-lang.org/edition-guide/editions/ 58.. [rust-unstable-features] https://github.com/Rust-for-Linux/linux/issues/2 59