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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]_ | |
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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>`. | |
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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 | ||
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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 | ||
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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 | ||
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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 | |
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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 | |
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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 |