blob: 5fc9160ca1fa5b3054887d59e7336941d51d3a5e [file] [log] [blame]
.. _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.
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]
.. [gcc]
.. [clang]
.. [icc]
.. [gcc-c-dialect-options]
.. [gnu-extensions]
.. [gcc-attribute-syntax]
.. [n2049]