Active Development · M2 Achieved

c3 — The Next-Gen
VB6 Compiler

Modern compiler that takes your VB6 code to the x64 era — with Unicode, multi-threading, and zero-modification compilation built in.

x64 · Unicode · Multi-threaded · Zero modification

Download Explore Features →
8,178
Lines of Code
80+
AST Node Types
14
Precedence Levels
200+
RTL Functions Planned
Why c3

c2 → c3: Three Generations of Progress

VB6's original compiler c2.exe targets x86 only. c3.exe brings three fundamental upgrades.

Capability c2.exe (VB6) c3.exe (vb6c3)
Architecture x86 (32-bit) x64 (64-bit) NEW
String Encoding ANSI / BSTR Unicode (UTF-16) NEW
Threading Single / STA Multi-threaded NEW
Runtime MSVBVM60.dll Static-linked (no DLL)
Debug Info PDB PDB (MSVC native)
C Code Output No Yes (debuggable)
Core Features

Everything VB6 Needs for the Modern Era

No source code modification required. Your VB6 projects compile as-is.

Native x64 Compilation

Generate 64-bit Windows executables and DLLs. Break the 2GB memory barrier. Direct x64 COM interop via MSVC ABI.

First-Class Unicode

BSTR strings are UTF-16 throughout. Source files support UTF-8/GBK/UTF-16 encoding with automatic detection.

Multi-threaded Runtime

No more single-threaded apartment model. Free-threaded COM, CreateThread, and true parallel execution.

VBA Compilation

Compile VBA code alongside VB6 projects. Supported as a first-class compilation target.

Static-Linked RTL

No runtime DLL dependency. All 200+ VB6 runtime functions are compiled directly into your executable. Clean deployment.

Safe Compilation

Unsupported syntax always reports an error. Never silently miscompiles. Miscompilation is worse than no compilation.

How It Works

VB6 Source → Native Binary

C code generation + MSVC gives you readable, debuggable output with zero external dependencies.

📄
VB6 Source
→
🔍
Lexer
→
🌳
Parser
→
📎
AST
→
🛠
Semantic
→
💻
C Code
→
⚡
cl.exe
→
🚀
.exe/.dll
Roadmap

Development Progress

Milestone-driven development. Every phase must pass verification before advancing.

M1

P0 — Infrastructure

CMake build, diagnostics, source manager (GBK/UTF-8/UTF-16), LL(2) lexer, compiler driver

Completed
M2

P1 — Parser & AST

Recursive descent + Pratt (14 levels), 80+ AST nodes, soft keywords, ~2900 lines parser code

Completed
P2

P2 — Semantic Analysis

Symbol table, type system, Variant inference, default property resolution, type checking

Next Up
P3

P3 — C Code Generation + MSVC

VB6→C type mapping, expression/stmt/proc codegen, cl.exe + link.exe driver

Planned
P4

P4 — Runtime Library (RTL)

BSTR, Variant, SAFEARRAY, 200+ runtime functions, all statically linked

Planned
P6

P6 — VBA Compilation Support

Compile VBA code from Office documents as first-class target

Planned
Command Line

Developer-Friendly CLI

Clean, composable command-line interface designed for CI/CD pipelines and build automation.

  • --dump-tokens Inspect lexer output
  • --dump-ast Visualize parse tree
  • --syntax-only Fast syntax validation
  • --target win-x64 Cross-target support
  • -O2 -g Optimize + debug info
$ c3 hello.bas --dump-ast
Module: hello.bas
  Sub Main (access=Public)
    LocalDecl → Dim name As String
    Assign: name = "World"
    If → Else → End If
    For i = 1 To 10 → Next i
    ✓ 0 errors, 0 warnings

$ c3 hello.bas -o hello.exe -O2
✓ Compiled: hello.exe (x64)

Ready to Bring VB6 to x64?

c3 is under active development. Follow progress or try the latest build.

Coming Soon View Roadmap →