Question
Answer and Explanation
The requirement for "ninja" in loading C extensions isn't a strict necessity in all cases, but it is often a key part of the build system used by many projects that include C extensions, especially in the Python ecosystem. Let's break down why Ninja is frequently preferred and how it relates to the process of loading C extensions.
1. C Extensions and Compilation:
- C extensions are typically written in C or C++ and need to be compiled into machine code (.so or .dll files) before they can be imported and used by a higher-level language like Python. This compilation process requires a build system.
2. Build Systems and Their Role:
- A build system is a tool that manages the compilation process. It figures out the dependencies between source code files, what needs to be compiled, and in which order to perform these steps, along with linking resulting objects into a final shared library. Examples of build systems are Make, CMake, Meson, and Ninja.
3. Why Ninja is Favored:
- Speed: Ninja's primary goal is speed. It was designed to minimize the time taken to perform builds, making it much faster than traditional build systems like Make, especially for complex projects. This speed is beneficial when dealing with frequent code changes and rebuilds, often the case in active development cycles.
- Simplicity: While Ninja itself has a simple input format, it is often used as a backend by higher-level build system generators such as CMake or Meson. This lets developers write their build configurations in a more descriptive way, while taking advantage of Ninja’s performance for the actual build.
- Modernity: Ninja does not interpret the build files for every single rebuild (unlike Make) instead, it directly parses a build description and therefore avoids bottlenecks.
4. The Workflow (Typically):
- A higher-level build system generator like CMake will parse and process high-level build descriptions written by developers, and then generates `.ninja` files. These `ninja` files contain the specific build steps. Once generated, these `ninja` files are given to the `ninja` command, which then runs all the operations needed to build the C extension.
5. Loading C Extensions in Python:
- After the C extensions are successfully built by the build system (with Ninja being a likely backend), they are then importable as modules within Python. If you are dealing with a Python project that uses C extensions, the extension must be built into shareable files first.
6. Why Not Directly Using Other Build Systems:
- While it is possible to use other build systems, Ninja's speed and integration with higher-level build system generators make it a popular choice, especially in ecosystems where projects rely heavily on compiled components.
7. In Summary
While the C extension loading does not directly require “ninja”, it is often an integral part of the C extension build process via higher-level build system generators like CMake, due to its speed and efficiency when building shareable files. Thus, the "ninja" tool is necessary for many modern workflows, particularly when working on cross-platform C extensions.