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