Question
Answer and Explanation
Ninja is a small build system designed for speed, and it's often used in conjunction with CMake. When you use CMake to generate build files, you can configure it to output Ninja build files instead of Makefiles or Visual Studio project files. Here's a breakdown of what Ninja is and its role with CMake:
What is Ninja?
Ninja is a build system focused on performance. Unlike more feature-rich systems like Make, Ninja's primary goal is to be fast and efficient at handling build processes. It works based on a directed acyclic graph (DAG) of dependencies. Ninja reads a build file and then executes commands in the optimal order to build the project, parallelizing where possible.
Key characteristics of Ninja include:
- Speed: Ninja's streamlined design and parallelization capabilities make builds significantly faster than traditional build systems in many scenarios.
- Simplicity: Ninja's file format is simple and well-defined, making it easy to generate and understand.
- Direct Execution: It focuses on executing commands directly based on the dependency graph, making it less complex than some other build systems.
How does Ninja work with CMake?
CMake is a meta-build system, which means it doesn't build software directly. Instead, it generates the build files (like Makefiles or Ninja build files) that another tool then uses to perform the actual build. When used with Ninja, CMake's role is to:
1. Configure: CMake reads the `CMakeLists.txt` file, which defines your project's structure, sources, and dependencies.
2. Generate: Instead of generating Makefiles or project files, it generates a `build.ninja` file when specified to use the Ninja generator.
3. Hand Off: CMake then relies on Ninja to execute the build commands defined in the `build.ninja` file.
To specify the Ninja generator with CMake, you typically use the `-G Ninja` option when configuring your project from the command line like this:
cmake -G Ninja <path-to-source-directory>
After the configuration, you run ninja command inside your build folder, which then executes the build.
Why use Ninja with CMake?
- Faster Builds: Ninja's design often results in much faster builds, especially for large projects.
- Improved Performance: Parallel execution of build commands can significantly reduce build times.
- Simplicity: Ninja simplifies the build process by focusing solely on building the code without excessive features.
In Summary, Ninja is a fast and efficient build system that works with CMake to build your software. CMake handles the configuration and project setup, and Ninja ensures that the actual build process is as quick and efficient as possible, making it a very popular option for modern software development.