1 .. _programming_language: 2 3 Programming Language 4 ==================== 5 6 The kernel is written in the C programming language [c-language]_. 7 More precisely, the kernel is typically compiled with ``gcc`` [gcc]_ 8 under ``-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 12 This dialect contains many extensions to the language [gnu-extensions]_, 13 and many of them are used within the kernel as a matter of course. 14 15 Attributes 16 ---------- 17 18 One of the common extensions used throughout the kernel are attributes 19 [gcc-attribute-syntax]_. Attributes allow to introduce 20 implementation-defined semantics to language entities (like variables, 21 functions or types) without having to make significant syntactic changes 22 to the language (e.g. adding a new keyword) [n2049]_. 23 24 In some cases, attributes are optional (i.e. a compiler not supporting them 25 should still produce proper code, even if it is slower or does not perform 26 as many compile-time checks/diagnostics). 27 28 The kernel defines pseudo-keywords (e.g. ``__pure``) instead of using 29 directly the GNU attribute syntax (e.g. ``__attribute__((__pure__))``) 30 in order to feature detect which ones can be used and/or to shorten the code. 31 32 Please refer to ``include/linux/compiler_attributes.h`` for more information. 33 34 Rust 35 ---- 36 37 The kernel has experimental support for the Rust programming language 38 [rust-language]_ under ``CONFIG_RUST``. It is compiled with ``rustc`` [rustc]_ 39 under ``--edition=2021`` [rust-editions]_. Editions are a way to introduce 40 small changes to the language that are not backwards compatible. 41 42 On top of that, some unstable features [rust-unstable-features]_ are used in 43 the kernel. Unstable features may change in the future, thus it is an important 44 goal to reach a point where only stable features are used. 45 46 Please 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
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