OpenRBX

A decompilation of Roblox as it shipped in December 2007. The aim is to rebuild the original binaries instruction for instruction, and to end up with a tree worth building on afterwards.

Conventions and tooling follow the LEGO Island decompilation.

Note: The code here reproduces the original release and does not try to improve on it. 32-bit Windows only.

Status

Still early. WebService.dll contains 12,633 functions. We are decompiling RBXGS first since the client contains no debug symbols.

Building

Visual C++ 8.0 SP1 compiled the original and is the only toolchain that reproduces its output, so contributions are measured against it.

Prerequisites

• Visual C++ 8.0 SP1. MSVC800-SP1 is a portable copy that requires no installation.
• CMake, either standalone or from the "Desktop development with C++" workload of a current Visual Studio.

Compiling

Open a command prompt and run Common7\Tools\vsvars32.bat from the toolchain to set the environment. VC\bin\vcvars32.bat will not do, as it defers to %VS80COMNTOOLS% and expects a registered installation.

Then configure and build:

cmake -B build -G "NMake Makefiles" -DCMAKE_BUILD_TYPE=RelWithDebInfo
cmake --build build

RelWithDebInfo keeps the debug symbols that further decompilation work depends on, and NMake Makefiles is the generator that copes with a toolchain of this age. The result is build\WebService.dll.

Verification

To compare a build against the original, install our fork of reccmp:

pip install -r tools/requirements.txt

Point it at your copy of the original through reccmp-user.yml in the project root:

targets:
  WEBSERVICE:
    path: path/to/WebService.dll

Then:

reccmp-reccmp --target WEBSERVICE -S WEBSERVICEPROGRESS.SVG

Project Structure

• WebService/ - The RBXGS-specific translation units
• common/ - Engine static libraries, one directory per .lib the original link consumed
• 3rdparty/ - Vendored dependencies
• util/ - Headers supporting the decompilation itself
• cmake/ - CMake modules
• tools/ - Python tooling and its requirements
• reccmp/ - Data sources for reccmp
• assets/ - Icons for the progress report

Target Binary

Binary	Size	SHA256
WebService.dll	3,461,120 bytes	5e9c6b82605fc8429c5fc5f682f2d7f98b55b73d993dfba58437365754410e2f

Version 0.3.676.0, dated December 20, 2007.

Contributing

Contributions are welcome. The conventions in short:

• Annotate decompiled code with reccmp markers (FUNCTION:, STUB:, GLOBAL:)
• Order functions within a translation unit by ascending address
• Place each file at the path WebService.pdb records for it
• Follow the clang-format configuration
• Take names from the PDB where it has them, and use NCC placeholders (FUN_XXXXXXXX, g_unk0xXXXXXXXX) only where it does not
• Keep pull requests small and focused

You can view CONTRIBUTING.md for more details!