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Case study

vf2-decomp: differentially validated Virtua Fighter 2 recovery

Recovers Virtua Fighter 2 Version 2.1’s Sega Model 2A i960 program into portable, non-matching C17, accepting each recovered path only when it matches a reference i960 executor at controlled boundaries. The repository adds ROM validation, i960 and 68000 analysis tools, a bounded Model 2A hardware model and snapshot-based differential runners. README states that it is not yet a playable port; match flow, combat, physics, AI, rasterization and much of the audio remain open.

Requirements and limitations

  • README describes a clean-room, non-matching recovery whose native runtime preserves CPU, frame, counter and mutable-memory state through repeated scheduler and gameplay dispatches, including a 1,270,824-instruction post-scheduler corridor with no interpreted instructions. It explicitly does not claim complete decompilation, a playable executable, full Model 2/TGP emulation, SCSP DSP audio or every gameplay branch. Unverified paths fail closed with VF2_ERROR_UNSUPPORTED.
  • ROM-backed analysis and differential tests need a user-supplied, legally obtained copy of the supported arcade ROM set. config/vf2_v22_roms.csv records only filenames, sizes and hashes, and vf2rom verifies the set. The repository contains no Sega game data, and contributors must not commit ROMs or reconstructed region images.
  • Builds use CMake with a C17 compiler and warnings treated as errors, plus an optional sanitizer configuration. STATUS lists GCC/Clang CI, and README names native Windows MSVC as the canonical agent workflow. Setting VF2_ROM_DIR enables the ROM-backed CTest targets; otherwise only ROM-independent tests run.
  • The vf2i960 native-dispatch commands run the recorded differential milestones, and vf2cycles advances recovered C and the reference executor from a shared snapshot, stopping in strict mode at the first unsupported block, reference failure or state mismatch. STATUS reports MATCH for the third through sixth dispatches. CI runs only ROM-independent tests, so the ROM-backed results remain project-reported and were not rerun for this collection.
  • BSD-3-Clause covers the project’s code; MAME and public Intel i960 documentation serve as cross-references, not included source. docs/LEGAL.md discloses 301 original Sega symbol names, taken from a later Model 2 port DLL, as non-clean-room naming, and an untracked Sonic The Fighters disassembly is used only as a navigation aid. AGENTS.md addresses coding agents, but the reviewed sources establish no REA use.

About this entry

Type
Case study
Category
Independent reconstruction cases
Relationship
Independent reconstruction project
Targets
Game

Sources reviewed

The description was reviewed against primary sources. This does not establish runtime testing, security auditing or verified compatibility.

Primary sources

  1. README.md GitHub · celsowm/vf2-decomp · Revision 9a9f727
  2. LICENSE GitHub · celsowm/vf2-decomp · Revision 9a9f727
  3. docs/LEGAL.md GitHub · celsowm/vf2-decomp · Revision 9a9f727
  4. THIRD_PARTY.md GitHub · celsowm/vf2-decomp · Revision 9a9f727
  5. docs/STATUS.md GitHub · celsowm/vf2-decomp · Revision 9a9f727
  6. AGENTS.md GitHub · celsowm/vf2-decomp · Revision 9a9f727
  7. config/vf2_v22_roms.csv GitHub · celsowm/vf2-decomp · Revision 9a9f727
  8. .github/workflows/ci.yml GitHub · celsowm/vf2-decomp · Revision 9a9f727