Il2Cpp Generated Stubs

Output directory: libil2cpp/zlua/generated/ (build writes build-win64/.../zlua/generated/) Generator: Packages/com.code-philosophy.zlua/Editor/CppCodeGen/ Runtime load: LuaAppDomain::Initialize → *Bridge::Initialize

1. Design principles

Il2Cpp Player cannot JIT or use Method.Invoke. The Lua→C# hot path depends on build-time scanning of user assemblies, generating C++ stubs for each AOT-reachable signature, looked up at runtime via function-pointer tables.

Versus Mono (EMIT-MONO.md):

Il2Cpp	Mono
Build-time C++ codegen	Bind-time Expression.Compile
Reuse stubs by ReducedType signature	One specialized bridge per member; no shared ReducedType table
Artifacts in generated/	Logic in Runtime/Mono/Emit/

2. Generation entry: CodeGenerator.Generate

Editor/CppCodeGen/CodeGenerator.cs calls in order:

Order	Generator	Artifact
1	BuiltinScriptsCodegen	BuiltinScripts.inc
2	PropertyBridgdeCodegen	PropertyBridgeStub.h
3	MethodBridgeCodegen	MethodBridgeStub.h
4	DelegateBridgeCodgen	DelegateBridgeStub.h
5	MarshalAsCodegen	MarshalBindings.h/.cpp ([LuaMarshalAs] extensions)

Unity Editor Il2Cpp builds write into target zlua/generated/; do not hand-edit generated files.

3. MethodBridgeStub.h

3.1 Analysis

MethodBridgeAnalyzer.Collect walks non-generic types/methods in user assemblies, skips .cctor, and builds MethodBindingInfo per MethodDef:

• uniqueName / stubName (NameUtil.CreateStubName)
• Parameter/return ParamMarshalInfo / LuaMarshalMetaInfo (MarshalMetaUtil)

3.2 Artifact structure

namespace methodbridge {
struct MethodBridgeEntry {
    const char* stubName;
    FnLua2CsInvoker lua2CsInvoker;
};
static const MethodBridgeEntry g_methodBridges[] = {
    { "Stub_MyType_DoWork_int", Bridge_MyType_DoWork_int },
    ...
    { nullptr, nullptr }
};
}

Each Bridge_* function:

• Pops arguments from the Lua stack (typed writers or inline primitives);
• alloca / stack layout;
• Calls method->invoker_method(...);
• Pushes the return value.

3.3 Runtime registration

MethodBridge::Initialize() walks g_methodBridges into AppendOnlyStringHashMap<FnLua2CsInvoker>.

MethodBridge::ResolveMethodInvoker(method) looks up stubName by ReducedType signature; on miss, falls back to DefaultInvokeLuaMethod (alloca + MarshalMeta writers, slower).

MetaBinding::CreateMethodMarshalCtx writes the resolved result into MethodMarshalCtx::lua2CsInvoker.

4. PropertyBridgeStub.h

Generates FnPropertyGetter / FnPropertySetter function-pointer tables for property getters/setters.

PropertyBridge::Initialize() registers; MetaBinding fills PropertyMarshalCtx::getter/setter.

Fields do not get a separate stub table: field R/W uses MarshalMetaInfo::cs2luaWriter / lua2csWriter + offset (FieldMarshalCtx).

5. DelegateBridgeStub.h

Stub tables for C# delegate invoke and Lua function → delegate.

DelegateBridge::Initialize() loads at AppDomain level; aligned with ../../spec/marshal/09-FUNCTION.md.

6. C#→Lua (GetFunction)

Not under generated/. C#→Lua binds a module function as a closed delegate via LuaAppDomain.GetFunction<T> at runtime; Invoke goes through the Delegate bridge (same as ../../spec/marshal/09-FUNCTION.md. Il2Cpp and Mono share the same API.

7. MarshalBindings.*

MarshalAsCodegen generates extra writers/readers for non-default [LuaMarshalAs] signatures, referenced by stubs or MarshalMeta::Create.

Rules: ../../spec/marshal/02-MARSHAL-AS.md.

8. BuiltinScripts.inc

Embeds globals.lua, zlualib.lua, etc. as C string arrays; LuaEnv.cpp #includes them and dostrings in RegisterGlobals / RegisterZLuaApi.

Mono equivalent: Lvm/BuiltinScripts.cs loads same-named scripts from resources.

9. Failure policy

Scenario	Behavior
Signature cannot generate a stub (unsupported generic, etc.)	Codegen errors or skips with a record; do not emit a silent slow path into Player
Runtime stub table miss	DefaultInvokeLuaMethod (explicit slow path; add stubs in development)

Mono counterpart: cannot Emit → throw at bind time (see ../MONO.md D3).

10. Relation to MetaBinding / Indexer

• Stubs do not decide whether a member enters the indexer; MetaBinding still creates closure refs.
• Direct method closure upvalues include MethodMarshalCtx* → already-resolved lua2CsInvoker.
• Dispatch* only affects how the closure is obtained, not the stub body.

11. Related files

Path	Responsibility
Editor/CppCodeGen/CodeGenerator.cs	Top entry
Editor/CppCodeGen/MethodBridgeCodegen.cs	Method stubs
Editor/CppCodeGen/PropertyBridgdeCodegen.cs	Property stubs
Editor/CppCodeGen/DelegateBridgeCodgen.cs	Delegate stubs
bridge/MethodBridge.cpp	Stub table load
lvm/LuaAppDomain.cpp	Initialize order