Xenomai LibEVL on Fedora 39

What's this?

See https://evlproject.org/overview/

This is a port of libevl for Fedora 39 with Linux Kernel 6.10.10. You can find the sources and build system for Linux 6.10.10 here on Github:

https://github.com/steleman/xenomai-fc39

It's based on libevl release 49. That's because of the ABI Compatibility Level (36) required by the Linux Kernel 6.10.10's evl header files. You need to build and install the Xenomai Linux Kernel to use libevl.

I have made changes to include/evl/atomic.h. The original implementation created two different - and incompatible - types for the atomic_t type: one for C, the other for C++. The C++ Standard doesn't guarantee compatibility of std::atomic<T> with C11's _Atomic type until C++23. And that compatibility is not even guaranteed, it needs to be feature-tested:

https://en.cppreference.com/w/cpp/header/stdatomic.h

libevl might very well be used in mixed C / C++ development. This is a problem. I solved this problem by using compiler builtins for the atomic operations used in atomic.h. The builtins work identically in C and in C++, and atomic_t becomes a simple int. The Linux kernel only builds with GCC and / or GCC-compatible compilers. clang supports GCC's atomic builtins. Commercial compilers that can build the Linux Kernel - from Intel, AMD or ARM - are all based on clang at this point.

How to build?

See https://evlproject.org/core/build-steps/

1. Copy the shell script meson-build-libevl.sh to the directory above this one.
2. Run the script: ./meson-build-libevl.sh.
3. That's it. You have built libevl.