Building XiDOS

XiDOS is built with a cross toolchain on a modern host and produces DOS binaries.

Choosing a backend

XiDOS is hybrid (see ARCHITECTURE.md). Pick a backend with BACKEND=:

  • BACKEND=realmode (default) — 16-bit real mode via INT 21h. Build with a 16-bit cross toolchain; the reference is Open Watcom V2.
  • BACKEND=pmode — 32-bit protected mode. Build with TOOLCHAIN=djgpp. This is the backend that targets bash / GCC / TCC.
make                                   # realmode (default)
make BACKEND=pmode TOOLCHAIN=djgpp     # pmode on DJGPP

Reference toolchain: Open Watcom V2 (realmode)

  1. Install Open Watcom V2.
  2. Source its environment (owsetenv.sh on Unix-like hosts) so wcc, wlib, and wlink are on your PATH.

  3. From the repo root:

    make

    This produces libxidos.a (the runtime) and stages the public headers.

Protected-mode toolchain: DJGPP in Docker (pmode)

There is no native DJGPP for Apple Silicon, and building the cross-GCC from source is slow, so the toolchain lives in a small linux/amd64 container (emulated on arm64 via Docker Desktop / Rosetta). The container compiles; DOSBox on the host runs the resulting .EXE.

make djgpp-image     # docker build -t xidos-djgpp tools/djgpp  (once)

The image carries the prebuilt DJGPP release (i586-pc-msdosdjgpp-gcc, GCC 12.2.0) plus CWSDPMI.EXE. See tools/djgpp/Dockerfile.

Testing in DOSBox

DJGPP programs are DPMI clients and plain DOSBox provides no DPMI host, so the build stages CWSDPMI.EXE next to the program; the DJGPP stub loads it automatically.

make dos          # build SMOKE.EXE, run it in DOSBox, capture & print C:\OUT.TXT
make dos-debug    # build, then drop into an interactive DOSBox shell (C: mounted)

make dos is the automated loop: DOSBox runs the program with stdout redirected to OUT.TXT, exits, and the host prints the captured text — no manual interaction. The DOSBox configs live in tools/dosbox/:

File Role
dosbox-xidos.conf machine / CPU / video settings (empty autoexec)
autoexec-run.conf automated: mount C:, run, capture, exit
autoexec-debug.conf interactive: mount C:, drop to a prompt

Running the host unit tests

The POSIX<->DOS path logic is host-buildable, so it is unit-tested with the host compiler — no DOS environment required:

make test

Alternative toolchains

  • DJGPP — a 32-bit protected-mode GCC port for DOS. Usable for the eventual pmode target; set TOOLCHAIN=djgpp.
  • GCC cross (ia16-elf) — experimental 16-bit GCC. Not yet wired up.

Notes

  • The Makefile defaults to Open Watcom; override with TOOLCHAIN=.
  • Real hardware testing is encouraged but optional. FreeDOS in a VM works well.