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=gnu89`` [gcc-c-dialect-options]_: the GNU dialect of ISO C90
9 ``clang`` [clang]_ is also supported, see docs !! 9 (including some C99 features).
10 :ref:`Building Linux with Clang/LLVM <kbuild_l <<
11 10
12 This dialect contains many extensions to the l 11 This dialect contains many extensions to the language [gnu-extensions]_,
13 and many of them are used within the kernel as 12 and many of them are used within the kernel as a matter of course.
14 13
>> 14 There is some support for compiling the kernel with ``clang`` [clang]_
>> 15 and ``icc`` [icc]_ for several of the architectures, although at the time
>> 16 of writing it is not completed, requiring third-party patches.
>> 17
15 Attributes 18 Attributes
16 ---------- 19 ----------
17 20
18 One of the common extensions used throughout t 21 One of the common extensions used throughout the kernel are attributes
19 [gcc-attribute-syntax]_. Attributes allow to i 22 [gcc-attribute-syntax]_. Attributes allow to introduce
20 implementation-defined semantics to language e 23 implementation-defined semantics to language entities (like variables,
21 functions or types) without having to make sig 24 functions or types) without having to make significant syntactic changes
22 to the language (e.g. adding a new keyword) [n 25 to the language (e.g. adding a new keyword) [n2049]_.
23 26
24 In some cases, attributes are optional (i.e. a 27 In some cases, attributes are optional (i.e. a compiler not supporting them
25 should still produce proper code, even if it i 28 should still produce proper code, even if it is slower or does not perform
26 as many compile-time checks/diagnostics). 29 as many compile-time checks/diagnostics).
27 30
28 The kernel defines pseudo-keywords (e.g. ``__p 31 The kernel defines pseudo-keywords (e.g. ``__pure``) instead of using
29 directly the GNU attribute syntax (e.g. ``__at 32 directly the GNU attribute syntax (e.g. ``__attribute__((__pure__))``)
30 in order to feature detect which ones can be u 33 in order to feature detect which ones can be used and/or to shorten the code.
31 34
32 Please refer to ``include/linux/compiler_attri 35 Please refer to ``include/linux/compiler_attributes.h`` for more information.
33 36
34 Rust <<
35 ---- <<
36 <<
37 The kernel has experimental support for the Ru <<
38 [rust-language]_ under ``CONFIG_RUST``. It is <<
39 under ``--edition=2021`` [rust-editions]_. Edi <<
40 small changes to the language that are not bac <<
41 <<
42 On top of that, some unstable features [rust-u <<
43 the kernel. Unstable features may change in th <<
44 goal to reach a point where only stable featur <<
45 <<
46 Please refer to Documentation/rust/index.rst f <<
47 <<
48 .. [c-language] http://www.open-std.org/jtc1/s 37 .. [c-language] http://www.open-std.org/jtc1/sc22/wg14/www/standards
49 .. [gcc] https://gcc.gnu.org 38 .. [gcc] https://gcc.gnu.org
50 .. [clang] https://clang.llvm.org 39 .. [clang] https://clang.llvm.org
>> 40 .. [icc] https://software.intel.com/en-us/c-compilers
51 .. [gcc-c-dialect-options] https://gcc.gnu.org 41 .. [gcc-c-dialect-options] https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
52 .. [gnu-extensions] https://gcc.gnu.org/online 42 .. [gnu-extensions] https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html
53 .. [gcc-attribute-syntax] https://gcc.gnu.org/ 43 .. [gcc-attribute-syntax] https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html
54 .. [n2049] http://www.open-std.org/jtc1/sc22/w 44 .. [n2049] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2049.pdf
55 .. [rust-language] https://www.rust-lang.org !! 45
56 .. [rustc] https://doc.rust-lang.org/rustc/ <<
57 .. [rust-editions] https://doc.rust-lang.org/e <<
58 .. [rust-unstable-features] https://github.com <<
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