watcom-compilers

Containerized historical Watcom C/C++ compilers — 6.5 (1988) through 11.0c (2002) — running on modern Linux, plus a byte-verified preservation index for the original distribution media.

Every image is produced by podman build with no host-side preprocessing: the full extraction, patching and installation pipeline runs inside container build stages, starting from the original retail media.

This repository contains no compiler media. scripts/fetch-sources.sh downloads it on demand from the consolidated Archive.org preservation item into archives/, verifying every file against scripts/SHA256SUMS before any build consumes it. That directory is a download target only — nothing under it is tracked. Provenance for each artifact lives in the Containerfile that uses it. The media are third-party proprietary binaries, not covered by this repository's license — see THIRD_PARTY.md.

Quick start

git clone https://github.com/second-impressions/watcom-compilers
cd watcom-compilers

scripts/fetch-sources.sh                  # download + verify media (~4 GB)
scripts/build-images.sh                   # build everything
scripts/build-images.sh --filter 11.0c    # ...or just one release

Then compile something:

# wibo — preferred where available (9.5 and later)
podman run --rm -v "$PWD:/src" localhost/watcom-11.0c-wibo \
    wcl386 -l=dos4g hello.c

# dosemu2 — also runs the produced binary
podman run --rm -v "$PWD:/src" localhost/watcom-11.0c-dosemu2 \
    wcl386 -l=dos4g hello.c
podman run --rm -v "$PWD:/src" localhost/watcom-11.0c-dosemu2 hello.exe

# interactive DOS prompt (dosemu2 S-Lang terminal over stdio)
podman run --rm -it -v "$PWD:/src" localhost/watcom-11.0c-dosemu2

Substitute any tag from the table below. With a command, the shim runs headless and exits on completion; with no command and a TTY, the dosemu2 images drop you at a DOS prompt with WATCOM / INCLUDE / PATH pre-set and F:\SRC as the working directory.

Prebuilt images

The toolchain images downstream projects use are published to the GitHub Container Registry, so you do not have to build anything to compile with them:

podman pull ghcr.io/second-impressions/watcom-10.0a-wibo
podman run --rm -v "$PWD:/src" ghcr.io/second-impressions/watcom-10.0a-wibo \
    wcl386 -l=dos4g hello.c

The shared bases (watcom-toolchain, watcom-dosemu2-runtime, watcom-wibo-runtime) are published too, tagged by a hash of their own definition; scripts/build-images.sh --bases-from ghcr.io/second-impressions reuses them so a local build skips recompiling wibo.

These images contain the original proprietary compiler binaries, which this repository's licence does not cover — see THIRD_PARTY.md. Build them yourself with the instructions below if you would rather not rely on a published artifact.

Which image should I use?

	*-wibo	*-dosemu2
How it works	runs the NT-host tools directly under a PE32 loader	boots a DOS environment and runs the DOS-host tools
Versions	9.5 → 11.0c (needs binnt/)	6.5 → 11.0c (all)
Speed	one exec, no emulation	DOS boot per invocation
Size (11.0c)	~435 MB	~536 MB
Runs its own output	no	yes

Prefer *-wibo where it exists: faster, smaller, no emulation — and it produces byte-identical output to the dosemu2 path.

Use *-dosemu2 for anything at or below 9.01e (those predate binnt/ entirely, so there are no NT-host tools for wibo to load), when you need to execute the produced DOS/4G binary — a wibo image compiles and links but has no DOS runtime — or when you want an interactive DOS prompt.

Versions covered

40 images in total: 24 dosemu2 and 16 wibo. ✓ = compiles, links and executes hello.c and hello.cpp in the tests/run-tests.sh matrix. C++ arrived in 10.0; earlier releases are C-only.

Version	Date	Media	dosemu2 image	wibo image
6.5	1988-05	✓	⚠ compile-only¹	— (16-bit)
7.0	1989-08	✓ archive-only	— (no linker²)	—
8.0	1990-06	✓ archive-only³	— (no extender³)	—
8.5	1991-09	✓	✓ tested	— (no binnt/)
9.0 NTA	1992-02	✓	✓ tested	— (no binnt/)
9.01	1992-05	✓	✓ tested	— (no binnt/)
9.01b	1992	✓ c386_b patch	✓ tested	— (no binnt/)
9.01c	1992	✓ c386_c patch	✓ tested	— (no binnt/)
9.01d	1992-11	✓	✓ tested	— (no binnt/)
9.01e	1993-02-28	✓ patch zip	✓ tested	— (no binnt/)
9.5 GA	1993-05-05	✓	✓ tested	✓ tested
9.5a	1993-08-27	✓	✓ tested	✓ tested
9.5b	1994-01-11	✓	✓ tested	✓ tested
9.5c	1994-06-30	✓	✓ tested	✓ tested
10.0 LA	1994-03-16	✓	✓ tested	✓ tested
10.0 GA	1994-05-31	✓ (tree only)	✓ tested	✓ tested
10.0a	1994-09-01	✓	✓ tested	✓ tested
10.0b	1995-01-11	✓	✓ tested	✓ tested
10.5	1995-07-11	✓	✓ tested	✓ tested
10.5a	1995-11	✓ c105_a patch	✓ tested	✓ tested
10.6	1996-02-29	✓⁴	✓ tested	✓ tested
10.6a	1997-01-10	✓	✓ tested	✓ tested
11.0	1997-02-11	✓	✓ tested	✓ tested
11.0a	1997-08-29	✓	✓ tested	✓ tested
11.0b	1998-02-24	✓	✓ tested¹	✓ tested
11.0c	2002-08-27	✓	✓ tested	✓ tested

Per-release notes

• 8.5/386 (1991) is the earliest fully self-contained Watcom toolchain: it bundles its own WLINK and the royalty-free Rational DOS/4GW 1.0 extender, so it compiles, links, and runs 32-bit DOS/4G programs end to end (wcl386 -l=dos4g; the output is run via the dos4gw loader). C-only — Watcom C++ did not arrive until 10.0.

• 6.5 (1988)¹ is the 16-bit DOS compiler. Its image builds and the compiler runs, but linking is blocked under dosemu2: the 1988 WLIB 1.1 / WLINK 4.1 reject the distribution's own (byte-perfect) OMF libraries — a real-mode file-I/O incompatibility with dosemu2's FDPP, not a bad dump. Kept as an experimental image; not in the test matrix.

• 7.0 (1989)² shipped as a code generator only — no linker. It targeted the Phar Lap 386|DOS-Extender (386|LINK + runtime) or A.I. Architects OS/386, both third-party SDKs. Without that linker the archive cannot produce a runnable binary, so 7.0 stays archive-only by design (this is a Watcom collection, not a mixed toolchain). The intended pairing is preserved separately at archive.org (phar-lap-386-dox-extender-4.1-sdk).

• All three were acquired from old-dos.ru; see SOURCES.md.

• The 9.5 32-bit floppy images (archive.org source) carry injected macOS .fseventsd metadata. An independent copy with a byte-identical Watcom payload and none of that noise is preserved alongside them on Archive.org; the build inputs are left unchanged.

• 10.0 GA ships as a pre-extracted install tree (recovered from Discmaster); the original floppy set has not surfaced. The watcom-10.0-ga-dosemu2 image uses the Sybase ZIP directly via extract-prebuilt-zip.sh; see containers/watcom-10.0-ga/dosemu2.Containerfile for the identity argument (BINB/wcc386.exe is 536,624 B — the pre-A-patch size).

• 10.5 is extracted directly from Watcom_C++_10.5.iso at container build time. The WPK v1.1 archives it uses are decoded by a pure-Python decoder at scripts/lib/wpack_decode.py; format and decoder details in docs/wpack.md.

• 10.5a shipped only as a maintenance patch (c105_a.zip), never as standalone media, which is why it eluded disc-image archives. The patch was recovered from the Watcom Products Infobase Vol 1 1996 CD and is applied onto the 10.5 GA tree at build time by scripts/apply-patches-10.5.sh (APPLYA: 367 patched, 19 created). The patched compiler self-reports "Version 10.5a"; see RESEARCH.md.

• 8.0 (1990)³ is C/386 with its own WLINK/WLIB/WMAKE but no bundled DOS extender (no DOS4GW/RUN386), so like 7.0 its 32-bit output cannot run standalone — archived and compilable, but no runnable image is built.

• 10.6 / 10.6a⁴. These are the same release except for the linker: 10.6a is 10.6 GA plus the documented "linker corrections for Win9x/NT". The compilers (WCC386.EXE/WPP386.EXE) are byte-identical between the two; only WLINK.EXE differs — 10.6 GA's is dated 1996-02-29, 10.6a's 1997-01-10. Both discs' README still say "version 10.6" (Sybase never bumped the banner), which long conflated them. The GA disc (archive.org ISO + physical rip) is archived as the 10.6 GA disc image; the 10.6a ZIP is archived alongside it. Both now build runnable images: 10.6 GA extracts from the ISO's DISKIMGS/ WPK packs (same path as 10.5), 10.6a from the pre-extracted ZIP. A full tree-vs-tree hash comparison confirmed the only differing common files are the three WLINK.EXE binaries. See cross-verification.md.

• 9.0 NTA (1992-02) and base 9.01 (1992-05) are self-contained C/386 toolchains (bundled WLINK + DOS4GW); their images compile, link, and run 32-bit DOS/4GW programs (wcl386 -l=dos4g). C-only.

• 9.01 patch levels. The May 1992 retail floppies are not pre-patch-A: APPLYA.BAT finds 50 files already stamped .a and errors on 15 more that are already past its expected input, while APPLYB.BAT applies to the same tree with 158 patched and zero errors. Since bpatch validates every input before touching it, the retail pressing already carried what c386_a was distributed to fix, and all files share a uniform 1992-05-28 date. So c386_a.zip applies to nothing in this collection and no 9.01a image exists; watcom-9.01b and watcom-9.01c chain c386_b and c386_c onto the retail tree. 9.01d comes from its own pre-extracted tree rather than from this chain — chaining b+c+d off the floppies reaches the same patch level but not a byte-equal tree, because the two install paths select different optional components. The 8.5-early (Liren c496 DOSIMG) and 9.0-mid (Liren c500 DiskDupe) dumps are proprietary-format duplicates of media already imaged here, so they are archived for preservation but not containerized.

• 9.5 pre-release (1993-02) is archive-only. The two preserved copies are disks 6 and 7 of the beta and nothing else: the DOS/OS2 and NT compilers, linker, librarian and make (including WPP386.NT, so C++ was already present three months before GA), but no headers, no libraries and no wlsystem.lnk. The compiler itself does run — unpacked with the DOS wpack.exe and pointed at 9.5 GA headers it compiles cleanly under wibo and reports "WATCOM C32 Optimizing Compiler Version 9.5, Copyright 1984, 1993" — but its linker rejects the GA system definitions (Error(3109): system block novell too large) and the beta's own are on a disk nobody has preserved. Any image would therefore be beta compilers on a GA runtime, which is not the release, so none is built.

• Not preserved: 6.0 (1987). 6.5 is the earliest surviving PC Watcom C. 6.0 is confirmed real (it appears in Open Watcom's own history) but no dump exists anywhere — not on WinWorld, Vetusware, os2site, old-dos, Discmaster or archive.org, and the one museum holding a "Version C6.0" box holds an empty one. Treat 6.5 as the practical floor.

• 11.0b¹ ships a broken wlink.exe that page-faults at startup under dosemu2. The container overlays the 11.0c wlink.exe on top of the otherwise-unmodified 11.0b tree as a one-file surgical patch. See containers/watcom-11.0/dosemu2.Containerfile for the full diagnosis. The 11.0b ISO itself is also non-compliant with strict ISO 9660 readers, so extraction goes through scripts/lib/iso_extract.py — a small tolerant ISO 9660 walker.

• wibo images cover every Watcom revision that ships a binnt/ directory — the full 9.5 – 11.0c range — by running the NT-host tools under the wibo PE32 loader (~7 MiB static binary, no Wine, no Xvfb, no Wine prefix). wibo is built from our pinned fork. An earlier Wine-based experiment was blocked by the 9.5 – 10.6a wlink.exe overlay pager / SEH incompatibility; wibo is unaffected by the same mechanism. 9.01d/e have no binnt/ so wibo is not applicable. See host-binary-taxonomy.md for the matrix of which host binaries are real vs. stubs vs. DLL launchers in every version.

Tree pruning

The 10.x and 11.x /opt/watcom trees are pruned at build time by scripts/lib/prune-watcom-tree.sh, which removes documentation, samples, IDE help catalogues, installer media and NetWare host pieces — ~30–60 MB on the early 10.x images and ~320 MB (~40 %) on the 11.0 family. It keeps every header, library and host tool, so the image can still compile, assemble, link, archive and make for every documented target (DOS, DOS/4G, Win 3.x, Win 9x, Win NT, OS/2, NetWare, NLM); that script's header carries the exact kept/dropped list.

Nothing is lost permanently: the original media stay byte-identified by scripts/SHA256SUMS and can be re-fetched at any time, and any image can be rebuilt with --build-arg PRUNE=0 to keep the complete tree under the same tag.

The 9.01 and 9.5 series are not pruned: those installs predate the bulk of what the prune script targets (no sdk/, no samples/, no mfc/, no big binw/ help catalogues), so the prune finds under 4 % to drop. Those images ship the unmodified tree.

Bundled DOS/4GW runtime versions

The DOS/4GW version bundled in a Watcom toolchain identifies the patch level used to build a given target executable. The version string appears at run time as DOS/4GW Protected Mode Run-time Version X.YY.

9.5 series

Image tag	Date	Compiler	Linker	DOS/4GW	Patch content
watcom-9.5-dosemu2	1993-05-05	wcc386 9.5	wlink 9.5	1.9 (240 580 B)	GA — unpatched
watcom-9.5a-dosemu2	1993-08-27	wcc386 9.5a	wlink 9.5a	1.92 (244 716 B)	APPLYA: 277 patched, 15 created
watcom-9.5b-dosemu2	1994-01-11	wcc386 9.5b	wlink 9.5b	1.95 (254 556 B)	APPLYB: 255 patched, 19 created
watcom-9.5c-dosemu2	1994-06-30	wcc386 9.5c	wlink 9.5c	1.97 (265 420 B)	APPLYC: 195 patched, 0 created

10.0 series

Image tag	Date	Compiler	Linker	DOS/4GW	Patch content
watcom-10.0a-dosemu2	1994-09-01	wcc386 10.0a	wlink 10.0	1.97 (254 556 B)	From retail ISO (earliest surviving level)
watcom-10.0b-dosemu2	1995-01-11	wcc386 10.0b	wlink 10.0	1.97 (254 556 B)	APPLYB: 57 patched (Pentium FDIV fix)

Media

scripts/build-media.txt lists the 56 artifacts needed to build every image. scripts/fetch-sources.sh downloads them from the Archive.org item and checks each against scripts/SHA256SUMS. Downloads land in a .part file and are only renamed into place after the hash matches, so an interrupted or corrupt download never replaces a valid input. Re-running is safe and normally verifies only.

--verify-only    fail instead of downloading missing or corrupt files
--force          re-download even valid files
--all            fetch every artifact in scripts/SHA256SUMS, not just the
                 subset the builds need (adds the archive-only media:
                 7.0, 8.0, the Liren dumps, the QNX 10.6b patch, ...)
--jobs N         concurrent downloads (default: 4)

scripts/SHA256SUMS is the single source of truth for identities; a path that is not listed there is a hard error rather than an unverified download.

Media must never be committed. The .gitignore rules are a safety net, not a guarantee — git ls-files archives should list only SHA256SUMS and provenance READMEs. Note that built images do contain the proprietary binaries even though this repository does not; publishing images is a separate decision from publishing this source.

Tests

tests/run-tests.sh                       # whole matrix
tests/run-tests.sh -f 11.0c              # one release
tests/run-interactive-tests.sh           # interactive DOS-prompt path

run-tests.sh compiles and links hello.c and hello.cpp with wcl386 -l=dos4g, then executes the result — wibo output is run in the matching dosemu2 image, which is also the check that both build paths produce identical bytes. Requires bats; nix develop provides it.

Continuous integration

Two workflows, both of which drive the same scripts a developer runs locally — there is no CI-only code path in the repository.

• pr.yml builds and verifies every image on each pull request, split into five parallel groups of eight. It also checks that the repository stays self-consistent: each image is named in the header of the Containerfile that builds it, each documented --target resolves to a real stage, every bind-mounted artifact appears in scripts/SHA256SUMS, and nothing under archives/ is tracked.
• publish.yml builds, verifies and pushes images to the GitHub Container Registry. The default set is the Watcom 10.0a pair: watcom-10.0a-wibo to compile DOS binaries and watcom-10.0a-dosemu2 to run them.

Third-party actions are pinned by commit SHA, matching how the base images are pinned by manifest digest.

One filter everywhere

scripts/images.tsv is the single build table. The same regex selects images for all four operations, so a CI job cannot fetch one set and test another:

F='^watcom-10\.0a-(wibo|dosemu2)$'
scripts/fetch-sources.sh --filter "$F"          # only the media those images need
scripts/build-images.sh --skip-fetch --filter "$F"
WATCOM_IMAGE_FILTER="$F" nix run .#test        # only those images
scripts/push-images.sh ghcr.io/OWNER --filter "$F" --tag sha-abc1234

The fetcher works out which media an image needs from the Containerfile's own bind mounts, following FROM localhost/… edges, so nothing has to be listed twice. For the pair above that is 4 files (~362 MB) rather than the full 54 (~3.4 GB) — which is what makes the CI media cache worth having, and keeps repeat runs off Archive.org.

A stale or partial cache is safe: fetch-sources.sh verifies every file against scripts/SHA256SUMS and re-downloads anything missing or corrupt, so a cache miss costs time and never correctness.

Documentation

Documentation sits next to the thing it describes:

• containers/wibo-runtime/Containerfile — which wibo fork/commit is built, and why
• scripts/shims/wibo-shim.sh — wibo's path, drive and DLL-search model
• scripts/shims/dosemu2-shim.sh — the DOS environment and shim branches
• scripts/lib/prune-watcom-tree.sh — the exact kept/dropped prune list
• each containers/*/dosemu2.Containerfile — provenance for the media it consumes
• docs/wpack.md — WPK archive format reference and decoder notes

Provenance and identification research is not duplicated here. It ships with the media it describes, in the Archive.org item: SOURCES.md, RESEARCH.md, cross-verification.md, host-binary-taxonomy.md and iso-identity.md.

License

Copyright (C) 2026 Simon Brakhane

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see https://www.gnu.org/licenses/.

This covers the build tooling, container definitions, tests and documentation authored here — SPDX-License-Identifier: AGPL-3.0-or-later. It does not cover the historical Watcom compiler media the build downloads, nor the third-party components the images are built from (dosemu2/FDPP, wibo, Debian, Ubuntu, Alpine). Those keep their own terms and are not relicensed; see THIRD_PARTY.md.