Kconfig Support in build2

Posted on 19 Jan 2021 by Boris Kolpackov with comments on r/cpp/

The build2 toolchain now includes a build system module that allows using the Linux kernel configuration system (Kconfig) to configure build2-based projects.

What is Kconfig?

Kconfig is the configuration system of the Linux kernel. Over the years it has evolved into a sophisticated variability modeling language and a toolset that are used by the Linux kernel to manage over ten thousand configuration options. It is also increasingly being used by other projects that need to manage complex configurations.

The Kconfig language defines a hierarchy of menus containing configuration options as well as relationships between them. For example:

config FANCY
        bool "Fancy options"
          Enable more fancy configuration options.

        string "Custom greeting"
        default "Hello"
        depends on FANCY
          Custom string to use as a greeting.

To create and manage configurations, the Kconfig system includes a number of tools called configurators. These provide both interactive (terminal and graphical) and non-interactive (default, random, etc) configuration methods, support for updating old configurations to new definitions (both interactively and non), as well as other configuration management facilities (creation of default configurations, etc).

See What is Kconfig for a more detailed overview and examples.

What is build2 Kconfig module?

The build2 Kconfig module acts as a second-level configuration mechanism to the builtin configuration support. Specifically, it integrates the execution of one of the Kconfig configurators into the build2 configure meta-operation and loads the resulting configuration file presenting its values as kconfig.* variables. We can then use these kconfig.* values to make decisions in buildfiles, testscripts, and/or propagate them to our source code, similar to the config.* values (Project Configuration).

See What is build2 Kconfig module for a more detailed overview and examples.

How to Try

The Kconfig functionality is available on all the supported platforms (including Windows). The kconfig module is part of the standard pre-installed build2 modules and is available starting with build2 version 0.14.0. If you would like to try it before 0.14.0 is released, use the staged version of the toolchain.

To get started, refer to the Introduction in The build2 Kconfig Module manual as well as the kconfig-hello example. See Kconfig Language for the description of the language.