GTA IV Recompiled (rexglue)

A static recompilation of the Xbox 360 version of Grand Theft Auto IV to native x86-64, built on the rexglue SDK (a Xenia-derived PowerPC→C++ recompiler + Xenos GPU runtime). PowerPC guest code is translated to C++ ahead of time; the kernel, GPU command processor, VFS and audio come from the rexglue runtime.

Status: early / experimental. The game boots, renders, and reaches interactive gameplay, but world collision does not load — the player falls through the ground (see Known issues). This repo is published so people with deeper RAGE-engine / recompilation knowledge can pick it up.

This project contains no game assets. You must provide files from your own legally-acquired Xbox 360 copy of GTA IV.

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What works

• Boots cleanly: 35,888 functions recompiled, 0 unresolved calls.
• Applies Title Update 8 at runtime (3.0.0.0 image → patched).
• Direct3D 12 renderer (via the rexglue Xenos runtime) initializes and presents.
• Full opening cinematic renders (characters, lighting, world streaming).
• Reaches interactive gameplay: HUD, radar, mission subtitles, pause menu.
• Keyboard/mouse input (emulated 360 controller).
• HDD cache partition is mounted so the world geometry streams and renders.

Known issues

What does not work

• World collision (static bounds) never loads → the player/vehicle falls through the ground ("the limbo"). Everything else (physics, AI, water collision) works; only the static-terrain phBound streaming is broken. This is the one blocking issue. See docs/COLLISION_BUG.md.
• Save games are enumerated from disk but rejected by the in-game menu (secondary issue).
• Audio: non-fatal XMA decode warnings.
• Android/other platforms: not attempted here. (rexglue already carries the ARM64/Android plumbing used by other ports, so it's a future option.)

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Building

This is not a clone-and-build repo — like every static-recompilation project, it cannot ship the game. A clone has no game/ data, no generated C++, and no SDK. You provide the game files, clone + patch the rexglue SDK, run codegen, then build. Follow the steps below and the Setup Guide.

Prerequisites

• Windows with:
  • LLVM/Clang (tested: 22.1.8) — clang/clang++
  • llvm-rc (ships with LLVM) for the resource compiler
  • MSVC Build Tools 2022 (for the Windows SDK headers/libs)
  • CMake ≥ 3.25, Ninja
  • Python 3 (used by the codegen title-update staging scripts)
• The rexglue SDK source tree and a built rexglue.exe codegen tool. It is public: mchughalex/rexglue-skate3 (branch skate3-sdk-clean). Point REXSDK_DIR at your clone (see docs/CMakeUserPresets.json.example). Apply docs/rexglue-sdk-gta4.patch to that clone — it adds two cvars GTA IV needs (mount_cache_device, invalid_call_nonfatal) as guarded additions:

  cd <your rexglue-skate3 clone>
  git apply /path/to/gta4recomp/docs/rexglue-sdk-gta4.patch
  

• ~40 GB free disk (game data 6.5 GB + generated C++ ~170 MB + build tree).

1. Provide the game files and assemble the folders

Fastest path — one script does extraction + staging + codegen:

python setup.py --iso "GTA IV.iso" --tu "TU_...0205" --rexglue path/to/rexglue.exe

Or do it by hand: ➡️ the step-by-step Setup Guide covers extracting the XGD2 disc into game/, staging the Title Update 8 image in tu8/, and populating update/ — using the pure-Python tools in tools/ (no external dependencies). Either way you build:

game/     extracted Xbox 360 disc root (default.xex, *.rpf, common/, xbox360/)
tu8/      default.xex + default.xexp (Title Update 8) as siblings
update/   the rest of the TU8 payload (data/, shaders/, text/)

TU8 media id is 6AC07221 and must match your disc.

2. Generate the recompiled C++

Run from the project root (paths in the manifest are relative on purpose):

rexglue codegen gta4_manifest.toml

This writes ~86 generated/default/gta4_recomp.*.cpp files (~170 MB).

3. Configure & build

Point CMakeUserPresets.json at your rexglue SDK tree, then:

cmake --preset win-amd64
cmake --build out/build/win-amd64 -j 2

Use a low -j (2) on machines with ≤ 8 GB RAM: the generated translation units are large and the LLVM optimizer is memory-hungry.

4. Run

Place a gta4.toml next to gta4.exe (see docs/gta4.toml.example) pointing at your game/, update/ folders, then run gta4.exe.

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Repository layout

CMakeLists.txt            Project build (arch baseline + rexglue glue)
CMakePresets.json         Standard presets (win/linux/mac × debug/rel)
gta4_manifest.toml        Codegen manifest (entrypoint, TU8, includes)
src/
  main.cpp                REX_DEFINE_APP entry
  gta4_app.h              App class (overrides rex::ReXApp)
config/
  gta4_functions.toml     Manual function-boundary fixes (3 branch targets)
  gta4_ctors.toml         1,454 static C++ constructors (reached only by a
                          pointer table the analyzer can't see)
  gta4_auto.toml          ~795 vtable/callback entry points
  gta4_ptrs.toml          Function addresses materialized in code (lis/addi)
  gta4_thunks.toml        16-byte virtual-dispatch thunks
tools/
  extract_xiso.py         Extract an Xbox 360 XDVDFS disc image (pure Python)
  extract_stfs.py         Extract an STFS package: TU or save (pure Python)
docs/
  SETUP.md                Step-by-step: disc -> game/tu8/update folders
  COLLISION_BUG.md        Deep dive on the blocking collision bug
  gta4.toml.example       Runtime config template
  CMakeUserPresets.json.example
  libertyrecomp_gta4_config.toml   Reference config from the LibertyRecomp project

The config/*.toml files are the accumulated result of iterative bring-up: rexglue discovers most functions from .pdata, and these files add the entry points it can't reach statically (constructor tables, vtables, computed jumps).

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Notes & references

• LibertyRecomp (OZORDI/LibertyRecomp) is a parallel GTA IV port on a fork of the same rexglue SDK. Its codegen config is preserved in docs/libertyrecomp_gta4_config.toml. Independently, it declares the same 3 unresolved branch targets this project found (0x8217C108, 0x82A77E28, 0x8219E410) and also targets TU8 — cross-validating the approach.
• The [rexcrt] mechanism (replacing the game's static CRT memset/memcpy/… with native implementations) was tested here; it did not affect the collision bug, so it was left out to keep the tree minimal.

Legal

This project distributes no copyrighted material. It is a recompiler front-end; you must own GTA IV for Xbox 360 and supply the files yourself. Trademarks belong to their respective owners.