What is gn in text?

GN: A Meta-Build System

GN is a meta-build system used primarily for generating Ninja build files. Google developed it to address the limitations of other build systems like Make and CMake, particularly for large projects like Chromium. Key aspects of GN include:

• Purpose: GN's main job is to produce Ninja build files. Ninja is a small build system that executes the build steps described in those files extremely quickly. GN is not the build system that does the actual compiling, linking, etc.; it's just there to create the Ninja input files.

• Language: The GN language is designed to be simple and easy to learn. It's declarative, meaning that you describe what you want to build, not the steps required to build it. It focuses on clarity and maintainability.

• Workflow: Typically, a developer writes GN build files (BUILD.gn) to describe the components of their project, dependencies, and build configurations. These files are then processed by the gn gen command, which generates Ninja files. Finally, Ninja is invoked to perform the actual build.

• Key Concepts: Some core ideas in GN are:

  • Targets: Represent buildable units, such as libraries, executables, and tests.
  • Scopes: Define the visibility of variables and targets. Variables defined in inner scopes override same-named variables in outer scopes.
  • Templates: Allow for the creation of reusable build configurations.
  • Functions: Enable the implementation of more complex build logic. They are used to perform actions in the build graph.

• Benefits: GN offers advantages like faster configuration times compared to some other meta-build systems, a simpler language, and better maintainability.

• Usage: GN is prominently used in the Chromium project, but it's also applicable to other C++ projects and beyond.