matheusgomes28 / cmake-cpp-modules

Skeleton project for C++20 modules CMake projects

C++20 Modules with MSVC and Clang, Using CMake

This repository provides a guide on how to use C++20 modules with both the MSVC and Clang compilers in CMake projects. C++20 modules with CMake is an experimental feature that allows for improved code organization, faster builds, and better encapsulation compared to traditional header files and preprocessor-based inclusion.

Above all, modularisation is a modern feature in many newer programming languages. This git repo wil help you practice using this new C++ feature.

For more in-depth information on modules, check out the video: "Thoughts on Compiler Support for C++20 Modules"

Prerequisites

Before proceeding, ensure that the following tools and versions are installed on your system:

• CMake (version 3.25 or later)
• A recent version of MSVC
• Clang compiler (16 or above)

Notes

C++20 modules are still an experimental feature in both MSVC and Clang compilers. In addition, it is also an experimental feature in CMake.

Therefore, some features may not be fully supported or might behave differently compared to traditional header files. Always check the compiler documentation and release notes for updates on the status and stability of C++20 modules. For your convenience, the list in the folllowing section provides useful resources regarding the support of modules in CMake and the main compilers.

• CMake's modules support article (a must read)
• Compiler feature support for checking which compiler versions support modules. As a quick check, look out for "Standard Library Modules", as when this is supported by your compiler, modules will probably be somewhat stable in that version.
• CMake experimental feratures guide to check for the correct GUID for the CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API flag. Make sure to substitute the version in the URL with your CMake version. Important!!!*

GCC Modules

Really hard to get a version that supports the features needed for modules. There seems to be a patched version, which is now quite out of date compared to the current trunk.

You will get the "unsupported flag...." pointing to the dependency scanning files if yout GCC version does not support modules.

CMake hacks required seem to be a lot more cumbersome compared to the Clang & MSVC versions.

If you are interested in using GCC with modules support, tatke a look on how to build your own patched GCC with Kitware's modules article (link above).

Clang Modules

The earliest version supporting modules fully seems to be 16. Need to go through hoops if you want to install in Ubuntu 18/22

Integration seems pretty good, however no standard library import modules, so you still need the include.

No hard CMake hacks are needed for module support with Clang, apart from setting the experimental features and the correct GUID thing.

MSVC

Support for modules in the MSVC compiler seems to be up to date, and in my opinion, it is the best compiler for working with Modules in C++.

Aside from selecting the MSVC compilers for CMake configuration and generation, there's no extra work to be done and the code in this repo should just compile.

Contributing

If you would like to contribute to this repository, please follow the standard GitHub fork and pull request workflow.

License

This project is licensed under the MIT License.

cmake-cpp-modules's Issues

Leave a link to the video

I'm here from the recent video Modules in C++ 20 - Thoughts on Compiler & CMake Support.

It has a lot of useful info that this repository doesn't have. How about adding link to it in the readme, so anyone that sees this repository can check it?

Adding more representative code examples to "my_lib"

Remove the copied and pasted code from the Kitware article, replace with code possibly containing:

• Templates
• Ranges from C++20
• More features available in C++20