Why Fels

I wanted a language that stays close to the machine, like C, but is harder to get wrong and easy to keep in your head. So Fels has a few ideas and tries to do them well:

• Memory lives in zones, and a zone is freed when its block ends.
• Errors are plain values that you check, not exceptions that fly past you.
• Code can run while the program compiles.
• One tool builds your project, runs its tests and fetches its packages.

Fels is young, and the language still changes. I write real programs in it; the biggest one is Strata, an app for my own investments. Building it turned up a lot of bugs in the compiler, and I fixed them along the way.

Where it stands

• Windows x64 works from end to end.
• Linux x64 works from end to end too: the compiler runs there and builds static executables.
• There is no macOS support and no formatter yet.
• -g gives a program debug info: source lines, functions, parameters and locals with their types, in a PDB on Windows and as DWARF on Linux. On Windows it needs the import libraries of the Windows SDK for now.
• Programs can run without an operating system, on x86-64 and 64-bit ARM: --target uefi makes a UEFI application and --target freestanding an ELF for a kernel, with interrupt handlers as functions.
• The safety checks stay on in release builds: index bounds, null pointers, integer overflow and division by zero, unless you ask for fels build --release-fast.
• CI runs the compiler’s tests on Windows and Linux on every push.

The known issues list what is still rough, and the changelog what changed in each release.

Tell me how it went

If you try Fels, I would love to hear about it. Open an issue for a bug, a question or an idea. Small programs that show a problem help the most.