Introduction

In this case study, we explore how the introduction of C++ Modules significantly improved the performance of a real-world project. C++ Modules is a new feature introduced in C++20 that aims to simplify the management of large codebases and improve compilation times.

The Problem

The project in question was a complex C++ application with a large codebase. As the project grew in size, the compilation times started to become a bottleneck in the development process. Compiling the entire codebase took a significant amount of time, often resulting in delays and frustration for the development team.

The Solution

To address the compilation time issue, the team decided to migrate the project to use C++ Modules. C++ Modules allow the compiler to generate pre-compiled modules for individual source files, which can then be reused across different translation units. This eliminates the need to repeatedly compile the same headers across multiple files.

Implementation

The team started by identifying the critical header files that were heavily used throughout the codebase. These headers were then transformed into modules using the module keyword. For example:

module mymodule;
import <iostream>;

void someFunction() {
    std::cout << "Hello, world!";
}

Once the critical headers were transformed into modules, the team updated the corresponding source files to import the modules instead. This allowed the compiler to generate and reuse pre-compiled modules during the compilation process.

Results

The introduction of C++ Modules had a significant impact on the performance of the project. The compilation times were reduced by up to 50%, resulting in faster build times and improved developer productivity. The team no longer had to wait for extended periods to compile the codebase, allowing them to iterate and test their changes more quickly.

In addition to the improved compilation times, the use of modules also led to a smaller executable size. By eliminating redundant code and reducing the need for header inclusion, the final binary size was significantly optimized.

Conclusion

The case study highlights the benefits of utilizing C++ Modules in a real-world project. By leveraging this new feature introduced in C++20, the team was able to significantly improve compilation times, resulting in faster build times and improved productivity. Additionally, the use of modules helped reduce the size of the final executable. As C++ Modules become more widely adopted, it is expected that more projects will benefit from their performance improvements.

#cpp #modules