Olympia TAG

TAG ("The Age of Gods") is the largest of the four Olympia play-by-mail (PBM) strategy game engines (~80K lines of C). It extends the base game with artifacts, religion, quests, hero skills, effects, mining, ranger skills, and ship crafting.

Sibling engine repositories:

• olympia-g1
• olympia-g2
• olympia-g3

This repository is a standalone extraction of the TAG engine from the original multi-engine Olympia monorepo. It builds on its own with CMake.

The code is legacy K&R-style C originally targeting 32-bit systems. The C11/64-bit modernization effort is complete: olympia-tag builds clean under the strict C11 warning ladder (all -Werror, zero warnings) and the golden flow runs clean under AddressSanitizer/UBSan.

Important

This is a modernization project, not a development project — no new features. The goal is to bring the existing TAG engine to clean C11 on 64-bit while preserving its exact behavior. Golden output is the contract: every change must keep the golden tests passing (byte-identical), and any behavior change must be deliberate, justified, and re-baselined in the same commit. New game features, gameplay tweaks, and scope expansion are out of bounds. See BUILD_HISTORY.md for the full modernization record.

Building

Requires CMake (>= 4.1), Ninja, and a Clang or GCC toolchain.

# Configure + build the default (debug) preset
cmake --preset debug
cmake --build --preset debug
# Binary: build/debug/olympia-tag

Other presets are defined in CMakePresets.json:

• debug — -O0 -g (default)
• release — -O3 -DNDEBUG
• asan-ubsan — AddressSanitizer + UndefinedBehaviorSanitizer (-O1 -g)

Without presets:

mkdir build && cd build && cmake .. && cmake --build .

32-bit build (Linux, for golden-file generation)

mkdir build32 && cd build32
cmake -DBUILD_32BIT=ON ..   # requires gcc-multilib
cmake --build .

Running / golden tests

run/olympia-tag.sh extracts the test fixtures (tests/olympia/fixtures/lib.tgz) into a scratch run/olympia/lib/ directory, loads the database in immediate mode, then runs a full -r -S turn. tests/olympia/golden_check.sh then gates the post-turn database against a committed sha256 manifest.

# Build first (default debug preset), then:
./run/olympia-tag.sh                          # extract fixtures, run a turn
./tests/olympia/golden_check.sh               # YES = byte-identical match
./tests/olympia/golden_check.sh --update      # re-baseline after a deliberate change

The scripts auto-detect the repo root and look for the binary at build/<preset>/olympia-tag (override the preset with OLYMPIA_PRESET=release ...). The same flow also runs under the asan-ubsan preset (OLYMPIA_PRESET=asan-ubsan ./run/olympia-tag.sh) — YES plus zero sanitizer diagnostics.

Layout

• olympia/ — the TAG engine sources and headers
• lib/ — shared support code (entity lists, tiles, roads, effects, allocation, …)
• tests/ — golden-test fixtures and the golden gate
• run/ — run/test driver script and scratch run directory
• doc/ — the TAG reference manual (r.texi) and the modernization plan
• CLAUDE.md — working guidance (build, test, conventions)
• BUILD_HISTORY.md — full phase-by-phase modernization record
• AUTHORS.md — authors and credits

Authors

See AUTHORS.md. Olympia was created by Rich Skrenta; this repository is maintained and modernized by Michael Henderson.

License

GNU Affero General Public License v3 — see LICENSE. The original Olympia sources are public domain.