1303d22c5SMiguel Ojeda.. _programming_language: 2303d22c5SMiguel Ojeda 3303d22c5SMiguel OjedaProgramming Language 4303d22c5SMiguel Ojeda==================== 5303d22c5SMiguel Ojeda 6303d22c5SMiguel OjedaThe kernel is written in the C programming language [c-language]_. 7303d22c5SMiguel OjedaMore precisely, the kernel is typically compiled with ``gcc`` [gcc]_ 8e8c07082SArnd Bergmannunder ``-std=gnu11`` [gcc-c-dialect-options]_: the GNU dialect of ISO C11. 9e8c07082SArnd Bergmann``clang`` [clang]_ is also supported, see docs on 10e8c07082SArnd Bergmann:ref:`Building Linux with Clang/LLVM <kbuild_llvm>`. 11303d22c5SMiguel Ojeda 12303d22c5SMiguel OjedaThis dialect contains many extensions to the language [gnu-extensions]_, 13303d22c5SMiguel Ojedaand many of them are used within the kernel as a matter of course. 14303d22c5SMiguel Ojeda 15303d22c5SMiguel OjedaAttributes 16303d22c5SMiguel Ojeda---------- 17303d22c5SMiguel Ojeda 18303d22c5SMiguel OjedaOne of the common extensions used throughout the kernel are attributes 19303d22c5SMiguel Ojeda[gcc-attribute-syntax]_. Attributes allow to introduce 20303d22c5SMiguel Ojedaimplementation-defined semantics to language entities (like variables, 21303d22c5SMiguel Ojedafunctions or types) without having to make significant syntactic changes 22303d22c5SMiguel Ojedato the language (e.g. adding a new keyword) [n2049]_. 23303d22c5SMiguel Ojeda 24303d22c5SMiguel OjedaIn some cases, attributes are optional (i.e. a compiler not supporting them 25303d22c5SMiguel Ojedashould still produce proper code, even if it is slower or does not perform 26303d22c5SMiguel Ojedaas many compile-time checks/diagnostics). 27303d22c5SMiguel Ojeda 28303d22c5SMiguel OjedaThe kernel defines pseudo-keywords (e.g. ``__pure``) instead of using 29303d22c5SMiguel Ojedadirectly the GNU attribute syntax (e.g. ``__attribute__((__pure__))``) 30303d22c5SMiguel Ojedain order to feature detect which ones can be used and/or to shorten the code. 31303d22c5SMiguel Ojeda 32303d22c5SMiguel OjedaPlease refer to ``include/linux/compiler_attributes.h`` for more information. 33303d22c5SMiguel Ojeda 34*0b02076fSMiguel OjedaRust 35*0b02076fSMiguel Ojeda---- 36*0b02076fSMiguel Ojeda 37*0b02076fSMiguel OjedaThe kernel has experimental support for the Rust programming language 38*0b02076fSMiguel Ojeda[rust-language]_ under ``CONFIG_RUST``. It is compiled with ``rustc`` [rustc]_ 39*0b02076fSMiguel Ojedaunder ``--edition=2021`` [rust-editions]_. Editions are a way to introduce 40*0b02076fSMiguel Ojedasmall changes to the language that are not backwards compatible. 41*0b02076fSMiguel Ojeda 42*0b02076fSMiguel OjedaOn top of that, some unstable features [rust-unstable-features]_ are used in 43*0b02076fSMiguel Ojedathe kernel. Unstable features may change in the future, thus it is an important 44*0b02076fSMiguel Ojedagoal to reach a point where only stable features are used. 45*0b02076fSMiguel Ojeda 46*0b02076fSMiguel OjedaPlease refer to Documentation/rust/index.rst for more information. 47*0b02076fSMiguel Ojeda 48303d22c5SMiguel Ojeda.. [c-language] http://www.open-std.org/jtc1/sc22/wg14/www/standards 49303d22c5SMiguel Ojeda.. [gcc] https://gcc.gnu.org 50303d22c5SMiguel Ojeda.. [clang] https://clang.llvm.org 51303d22c5SMiguel Ojeda.. [gcc-c-dialect-options] https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html 52303d22c5SMiguel Ojeda.. [gnu-extensions] https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html 53303d22c5SMiguel Ojeda.. [gcc-attribute-syntax] https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html 54303d22c5SMiguel Ojeda.. [n2049] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2049.pdf 55*0b02076fSMiguel Ojeda.. [rust-language] https://www.rust-lang.org 56*0b02076fSMiguel Ojeda.. [rustc] https://doc.rust-lang.org/rustc/ 57*0b02076fSMiguel Ojeda.. [rust-editions] https://doc.rust-lang.org/edition-guide/editions/ 58*0b02076fSMiguel Ojeda.. [rust-unstable-features] https://github.com/Rust-for-Linux/linux/issues/2 59