Documentation/process/programming-language.rst - linux - Git at Google

 .. _programming_language:

 Programming Language
 ====================

 The kernel is written in the C programming language [c-language]_.
 More precisely, the kernel is typically compiled with ``gcc`` [gcc]_
 under ``-std=gnu89`` [gcc-c-dialect-options]_: the GNU dialect of ISO C90
 (including some C99 features). ``clang`` [clang]_ is also supported, see
 docs on :ref:`Building Linux with Clang/LLVM <kbuild_llvm>`.

 This dialect contains many extensions to the language [gnu-extensions]_,
 and many of them are used within the kernel as a matter of course.

 There is some support for compiling the kernel with ``icc`` [icc]_ for several
 of the architectures, although at the time of writing it is not completed,
 requiring third-party patches.

 Attributes
 ----------

 One of the common extensions used throughout the kernel are attributes
 [gcc-attribute-syntax]_. Attributes allow to introduce
 implementation-defined semantics to language entities (like variables,
 functions or types) without having to make significant syntactic changes
 to the language (e.g. adding a new keyword) [n2049]_.

 In some cases, attributes are optional (i.e. a compiler not supporting them
 should still produce proper code, even if it is slower or does not perform
 as many compile-time checks/diagnostics).

 The kernel defines pseudo-keywords (e.g. ``__pure``) instead of using
 directly the GNU attribute syntax (e.g. ``__attribute__((__pure__))``)
 in order to feature detect which ones can be used and/or to shorten the code.

 Please refer to ``include/linux/compiler_attributes.h`` for more information.

 .. [c-language] http://www.open-std.org/jtc1/sc22/wg14/www/standards
 .. [gcc] https://gcc.gnu.org
 .. [clang] https://clang.llvm.org
 .. [icc] https://software.intel.com/en-us/c-compilers
 .. [gcc-c-dialect-options] https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
 .. [gnu-extensions] https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html
 .. [gcc-attribute-syntax] https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html
 .. [n2049] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2049.pdf
	.. _programming_language:

	Programming Language
	====================

	The kernel is written in the C programming language [c-language]_.
	More precisely, the kernel is typically compiled with ``gcc`` [gcc]_
	under ``-std=gnu89`` [gcc-c-dialect-options]_: the GNU dialect of ISO C90
	(including some C99 features). ``clang`` [clang]_ is also supported, see
	docs on :ref:`Building Linux with Clang/LLVM <kbuild_llvm>`.

	This dialect contains many extensions to the language [gnu-extensions]_,
	and many of them are used within the kernel as a matter of course.

	There is some support for compiling the kernel with ``icc`` [icc]_ for several
	of the architectures, although at the time of writing it is not completed,
	requiring third-party patches.

	Attributes
	----------

	One of the common extensions used throughout the kernel are attributes
	[gcc-attribute-syntax]_. Attributes allow to introduce
	implementation-defined semantics to language entities (like variables,
	functions or types) without having to make significant syntactic changes
	to the language (e.g. adding a new keyword) [n2049]_.

	In some cases, attributes are optional (i.e. a compiler not supporting them
	should still produce proper code, even if it is slower or does not perform
	as many compile-time checks/diagnostics).

	The kernel defines pseudo-keywords (e.g. ``__pure``) instead of using
	directly the GNU attribute syntax (e.g. ``__attribute__((__pure__))``)
	in order to feature detect which ones can be used and/or to shorten the code.

	Please refer to ``include/linux/compiler_attributes.h`` for more information.

	.. [c-language] http://www.open-std.org/jtc1/sc22/wg14/www/standards
	.. [gcc] https://gcc.gnu.org
	.. [clang] https://clang.llvm.org
	.. [icc] https://software.intel.com/en-us/c-compilers
	.. [gcc-c-dialect-options] https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
	.. [gnu-extensions] https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html
	.. [gcc-attribute-syntax] https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html
	.. [n2049] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2049.pdf