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- .. _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=gnu11`` [gcc-c-dialect-options]_: the GNU dialect of ISO C11.
- ``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
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