open-watcom-v2

Open Watcom V2 keeps the classic Watcom C, C++, and Fortran compiler alive and building. It's a full toolchain (compilers, linkers, assemblers, and a debugger) that still targets DOS, Windows, OS/2, and Linux from a single install. Open source under the Sybase Open Watcom license, free, and actively maintained by a community after the original openwatcom.org went dormant.

The reason anyone reaches for this in 2026 is target support nothing modern offers. If you're building for 16-bit DOS, OS/2, or other retro and embedded targets, Open Watcom compiles for them out of the box where GCC and Clang would need heavy coaxing or simply can't. Retro game developers, legacy industrial systems, and hobbyist OS projects are the core audience. Setup is a straightforward installer or build-from-source on a modern machine.

For mainstream C and C++ work, this isn't your compiler. GCC, Clang, and MSVC are faster, produce better code, and own the ecosystem. Open Watcom earns its place when the target matters more than raw optimization: shipping a DOS executable, maintaining an OS/2 application, or learning how compilers worked before LLVM. Free for everyone, hobbyist or commercial.

The catch: it's a preservation and niche-target project, not a competitor for modern development. Optimization and C++ standards support lag well behind the mainstream compilers, and the community is small. Use it because you need what only it can target, not because you expect cutting-edge codegen.