Index: test/wasm/call-indirect.ll
===================================================================
--- test/wasm/call-indirect.ll
+++ test/wasm/call-indirect.ll
@@ -52,7 +52,7 @@
 ; CHECK-NEXT:         ParamTypes:      
 ; CHECK-NEXT:           - I64
 ; CHECK-NEXT:   - Type:            FUNCTION
-; CHECK-NEXT:     FunctionTypes:   [ 0, 1, 0, 0, 2 ]
+; CHECK-NEXT:     FunctionTypes:   [ 0, 1, 0, 0, 2, 1 ]
 ; CHECK-NEXT:   - Type:            TABLE
 ; CHECK-NEXT:     Tables:
 ; CHECK-NEXT:       - ElemType:        ANYFUNC
@@ -114,6 +114,9 @@
 ; CHECK-NEXT:       - Index:           4
 ; CHECK-NEXT:         Locals:
 ; CHECK-NEXT:         Body:            42012000118380808000001A0B
+; CHECK-NEXT:       - Index:           5
+; CHECK-NEXT:         Locals:
+; CHECK-NEXT:         Body:            0B
 ; CHECK-NEXT:   - Type:            DATA
 ; CHECK-NEXT:     Segments:
 ; CHECK-NEXT:       - SectionOffset:    7
Index: test/wasm/function-imports-first.ll
===================================================================
--- test/wasm/function-imports-first.ll
+++ test/wasm/function-imports-first.ll
@@ -22,7 +22,7 @@
 ; CHECK-NEXT:        ParamTypes:
 ; CHECK-NEXT:          - F32
 ; CHECK:  - Type:            FUNCTION
-; CHECK-NEXT:    FunctionTypes: [ 0, 1 ]
+; CHECK-NEXT:    FunctionTypes: [ 0, 1, 0 ]
 ; CHECK:  - Type:            CODE
 ; CHECK-NEXT:    Functions:
 ; CHECK-NEXT:      - Index:           0
@@ -31,6 +31,9 @@
 ; CHECK-NEXT:      - Index:           1
 ; CHECK-NEXT:        Locals:
 ; CHECK-NEXT:        Body:            41000B
+; CHECK-NEXT:      - Index:           2
+; CHECK-NEXT:        Locals:
+; CHECK-NEXT:        Body:            0B
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
 ; CHECK-NEXT:     DataSize:        0
@@ -41,4 +44,6 @@
 ; CHECK-NEXT:         Name:            _start
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Name:            ret32
+; CHECK-NEXT:       - Index:           2
+; CHECK-NEXT:         Name:            __wasm_call_ctors
 ; CHECK-NEXT: ...
Index: test/wasm/function-imports.ll
===================================================================
--- test/wasm/function-imports.ll
+++ test/wasm/function-imports.ll
@@ -23,15 +23,18 @@
 ; CHECK-NEXT:        ReturnType:      NORESULT
 ; CHECK-NEXT:        ParamTypes:
 ; CHECK-NEXT:  - Type:            FUNCTION
-; CHECK-NEXT:    FunctionTypes:   [ 0, 1 ]
+; CHECK-NEXT:    FunctionTypes:   [ 0, 1, 1 ]
 ; CHECK:       - Type:            CODE
 ; CHECK-NEXT:    Functions:
 ; CHECK:           - Index:       0
 ; CHECK:           - Index:       1
+; CHECK:           - Index:       2
 ; CHECK:         Name:            name
 ; CHECK-NEXT:    FunctionNames:
 ; CHECK-NEXT:      - Index:           0
 ; CHECK-NEXT:        Name:            ret32
 ; CHECK-NEXT:      - Index:           1
 ; CHECK-NEXT:        Name:            _start
+; CHECK-NEXT:      - Index:           2
+; CHECK-NEXT:        Name:            __wasm_call_ctors
 ; CHECK-NEXT: ...
Index: test/wasm/init-fini.ll
===================================================================
--- test/wasm/init-fini.ll
+++ test/wasm/init-fini.ll
@@ -27,7 +27,16 @@
 ; RUN: lld -flavor wasm %t.o %t.global-ctor-dtor.o -o %t.wasm
 ; RUN: obj2yaml %t.wasm | FileCheck %s
 
-; CHECK:          Name:            linking
+; CHECK:        - Type:            ELEM
+; CHECK-NEXT:     Segments:        
+; CHECK-NEXT:       - Offset:          
+; CHECK-NEXT:           Opcode:          I32_CONST
+; CHECK-NEXT:           Value:           1
+; CHECK-NEXT:         Functions:       [ 4, 9 ]
+
+; CHECK:              Body:            100010051007100A0B
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            linking
 ; CHECK-NEXT:     DataSize:        0
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            name
@@ -54,6 +63,8 @@
 ; CHECK-NEXT:         Name:            .Lcall_dtors
 ; CHECK-NEXT:       - Index:           10
 ; CHECK-NEXT:         Name:            .Lregister_call_dtors
+; CHECK-NEXT:       - Index:           11
+; CHECK-NEXT:         Name:            __wasm_call_ctors
 ; CHECK-NEXT: ...
 
 
Index: test/wasm/local-symbols.ll
===================================================================
--- test/wasm/local-symbols.ll
+++ test/wasm/local-symbols.ll
@@ -24,8 +24,11 @@
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         ReturnType:      I32
 ; CHECK-NEXT:         ParamTypes:
+; CHECK-NEXT:       - Index:           1
+; CHECK-NEXT:         ReturnType:      NORESULT
+; CHECK-NEXT:         ParamTypes:   
 ; CHECK-NEXT:   - Type:            FUNCTION
-; CHECK-NEXT:     FunctionTypes:   [ 0, 0 ]
+; CHECK-NEXT:     FunctionTypes:   [ 0, 0, 1 ]
 ; CHECK-NEXT:   - Type:            TABLE
 ; CHECK-NEXT:     Tables:
 ; CHECK-NEXT:       - ElemType:        ANYFUNC
@@ -60,6 +63,9 @@
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Locals:
 ; CHECK-NEXT:         Body:            41010B
+; CHECK-NEXT:       - Index:           2
+; CHECK-NEXT:         Locals:
+; CHECK-NEXT:         Body:            0B
 ; CHECK-NEXT:   - Type:            DATA
 ; CHECK-NEXT:     Segments:
 ; CHECK-NEXT:       - SectionOffset:   7
@@ -78,4 +84,6 @@
 ; CHECK-NEXT:         Name:            baz
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Name:            _start
+; CHECK-NEXT:       - Index:           2
+; CHECK-NEXT:         Name:            __wasm_call_ctors
 ; CHECK-NEXT: ...
Index: test/wasm/stack-pointer.ll
===================================================================
--- test/wasm/stack-pointer.ll
+++ test/wasm/stack-pointer.ll
@@ -18,8 +18,11 @@
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         ReturnType:      I32
 ; CHECK-NEXT:         ParamTypes:
+; CHECK-NEXT:       - Index:           1
+; CHECK-NEXT:         ReturnType:      NORESULT
+; CHECK-NEXT:         ParamTypes:   
 ; CHECK-NEXT:   - Type:            FUNCTION
-; CHECK-NEXT:     FunctionTypes:   [ 0 ]
+; CHECK-NEXT:     FunctionTypes:   [ 0, 1 ]
 ; CHECK-NEXT:   - Type:            TABLE
 ; CHECK-NEXT:     Tables:
 ; CHECK-NEXT:       - ElemType:        ANYFUNC
@@ -46,6 +49,9 @@
 ; CHECK-NEXT:       - Name:            _start
 ; CHECK-NEXT:         Kind:            FUNCTION
 ; CHECK-NEXT:         Index:           0
+; CHECK-NEXT:       - Name:            __wasm_call_ctors
+; CHECK-NEXT:         Kind:            FUNCTION
+; CHECK-NEXT:         Index:           1
 ; CHECK-NEXT:   - Type:            CODE
 ; CHECK-NEXT:     Relocations:
 ; CHECK-NEXT:       - Type:            R_WEBASSEMBLY_GLOBAL_INDEX_LEB
@@ -55,6 +61,9 @@
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Locals:
 ; CHECK-NEXT:         Body:            23808080800041106B1A41000B
+; CHECK-NEXT:       - Index:           1
+; CHECK-NEXT:         Locals:
+; CHECK-NEXT:         Body:            0B
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
 ; CHECK-NEXT:     DataSize:        0
@@ -63,4 +72,6 @@
 ; CHECK-NEXT:     FunctionNames:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Name:            _start
+; CHECK-NEXT:       - Index:           1
+; CHECK-NEXT:         Name:            __wasm_call_ctors
 ; CHECK-NEXT: ...
Index: test/wasm/weak-alias-overide.ll
===================================================================
--- test/wasm/weak-alias-overide.ll
+++ test/wasm/weak-alias-overide.ll
@@ -30,7 +30,7 @@
 ; CHECK-NEXT:         ReturnType:      NORESULT
 ; CHECK-NEXT:         ParamTypes:
 ; CHECK-NEXT:   - Type:            FUNCTION
-; CHECK-NEXT:     FunctionTypes:   [ 0, 1, 0, 0, 0, 0, 0 ]
+; CHECK-NEXT:     FunctionTypes:   [ 0, 1, 0, 0, 0, 0, 0, 1 ]
 ; CHECK-NEXT:   - Type:            TABLE
 ; CHECK-NEXT:     Tables:
 ; CHECK-NEXT:       - ElemType:        ANYFUNC
@@ -108,6 +108,9 @@
 ; CHECK-NEXT:           - Type:            I32
 ; CHECK-NEXT:             Count:           2
 ; CHECK-NEXT:         Body:            23808080800041106B220024808080800020004182808080003602081082808080002101200041106A24808080800020010B
+; CHECK-NEXT:       - Index:           7
+; CHECK-NEXT:         Locals:
+; CHECK-NEXT:         Body:            0B
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
 ; CHECK-NEXT:     DataSize:        0
@@ -128,4 +131,6 @@
 ; CHECK-NEXT:         Name:            call_alias_ptr
 ; CHECK-NEXT:       - Index:           6
 ; CHECK-NEXT:         Name:            call_direct_ptr
+; CHECK-NEXT:       - Index:           7
+; CHECK-NEXT:         Name:            __wasm_call_ctors
 ; CHECK-NEXT: ...
Index: test/wasm/weak-alias.ll
===================================================================
--- test/wasm/weak-alias.ll
+++ test/wasm/weak-alias.ll
@@ -23,8 +23,11 @@
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         ReturnType:      I32
 ; CHECK-NEXT:         ParamTypes:
+; CHECK-NEXT:       - Index:           1
+; CHECK-NEXT:         ReturnType:      NORESULT
+; CHECK-NEXT:         ParamTypes:   
 ; CHECK-NEXT:   - Type:            FUNCTION
-; CHECK-NEXT:     FunctionTypes:   [ 0, 0, 0, 0, 0, 0 ]
+; CHECK-NEXT:     FunctionTypes:   [ 0, 0, 0, 0, 0, 0, 1 ]
 ; CHECK-NEXT:   - Type:            TABLE
 ; CHECK-NEXT:     Tables:
 ; CHECK-NEXT:       - ElemType:        ANYFUNC
@@ -99,6 +102,9 @@
 ; CHECK-NEXT:           - Type:            I32
 ; CHECK-NEXT:             Count:           2
 ; CHECK-NEXT:         Body:            23808080800041106B220024808080800020004182808080003602081081808080002101200041106A24808080800020010B
+; CHECK-NEXT:       - Index:           6
+; CHECK-NEXT:         Locals:
+; CHECK-NEXT:         Body:            0B
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
 ; CHECK-NEXT:     DataSize:        0
@@ -117,4 +123,6 @@
 ; CHECK-NEXT:         Name:            call_alias_ptr
 ; CHECK-NEXT:       - Index:           5
 ; CHECK-NEXT:         Name:            call_direct_ptr
+; CHECK-NEXT:       - Index:           6
+; CHECK-NEXT:         Name:            __wasm_call_ctors
 ; CHECK-NEXT: ...
Index: test/wasm/weak-symbols.ll
===================================================================
--- test/wasm/weak-symbols.ll
+++ test/wasm/weak-symbols.ll
@@ -23,8 +23,11 @@
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         ReturnType:      I32
 ; CHECK-NEXT:         ParamTypes:
+; CHECK-NEXT:       - Index:           1
+; CHECK-NEXT:         ReturnType:      NORESULT
+; CHECK-NEXT:         ParamTypes:   
 ; CHECK-NEXT:   - Type:            FUNCTION
-; CHECK-NEXT:     FunctionTypes:   [ 0, 0, 0, 0, 0 ]
+; CHECK-NEXT:     FunctionTypes:   [ 0, 0, 0, 0, 0, 1 ]
 ; CHECK-NEXT:   - Type:            TABLE
 ; CHECK-NEXT:     Tables:
 ; CHECK-NEXT:       - ElemType:        ANYFUNC
@@ -83,6 +86,9 @@
 ; CHECK-NEXT:       - Index:           4
 ; CHECK-NEXT:         Locals:
 ; CHECK-NEXT:         Body:            4181808080000B
+; CHECK-NEXT:       - Index:           5
+; CHECK-NEXT:         Locals:
+; CHECK-NEXT:         Body:            0B
 ; CHECK-NEXT:   - Type:            DATA
 ; CHECK-NEXT:     Segments:
 ; CHECK-NEXT:       - SectionOffset:   7
@@ -103,4 +109,6 @@
 ; CHECK-NEXT:         Name:            exportWeak1
 ; CHECK-NEXT:       - Index:           4
 ; CHECK-NEXT:         Name:            exportWeak2
+; CHECK-NEXT:       - Index:           5
+; CHECK-NEXT:         Name:            __wasm_call_ctors
 ; CHECK-NEXT: ...
Index: test/wasm/weak-undefined.ll
===================================================================
--- test/wasm/weak-undefined.ll
+++ test/wasm/weak-undefined.ll
@@ -33,8 +33,11 @@
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         ReturnType:      I32
 ; CHECK-NEXT:         ParamTypes:
+; CHECK-NEXT:       - Index:           1
+; CHECK-NEXT:         ReturnType:      NORESULT
+; CHECK-NEXT:         ParamTypes:   
 ; CHECK-NEXT:   - Type:            FUNCTION
-; CHECK-NEXT:     FunctionTypes:   [ 0, 0, 0 ]
+; CHECK-NEXT:     FunctionTypes:   [ 0, 0, 0, 1 ]
 ; CHECK-NEXT:   - Type:            TABLE
 ; CHECK-NEXT:     Tables:
 ; CHECK-NEXT:       - ElemType:        ANYFUNC
@@ -78,6 +81,9 @@
 ; CHECK-NEXT:       - Index:           2
 ; CHECK-NEXT:         Locals:
 ; CHECK-NEXT:         Body:            4100280280808080000B
+; CHECK-NEXT:       - Index:           3
+; CHECK-NEXT:         Locals:
+; CHECK-NEXT:         Body:            0B
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
 ; CHECK-NEXT:     DataSize:        0
Index: wasm/Config.h
===================================================================
--- wasm/Config.h
+++ wasm/Config.h
@@ -35,11 +35,13 @@
   uint32_t MaxMemory;
   uint32_t ZStackSize;
   llvm::StringRef Entry;
+  llvm::StringRef CtorFunction = "__wasm_call_ctors";
   llvm::StringRef OutputFile;
 
   llvm::StringSet<> AllowUndefinedSymbols;
   std::vector<llvm::StringRef> SearchPaths;
   Symbol *StackPointerSymbol = nullptr;
+  Symbol *CtorSymbol = nullptr;
 };
 
 // The only instance of Configuration struct.
Index: wasm/Driver.cpp
===================================================================
--- wasm/Driver.cpp
+++ wasm/Driver.cpp
@@ -273,15 +273,16 @@
     error("undefined symbols specified for relocatable output file");
 
   if (!Config->Relocatable) {
-    if (!Config->Entry.empty()) {
-      static WasmSignature Signature = {{}, WASM_TYPE_NORESULT};
+    static WasmSignature Signature = {{}, WASM_TYPE_NORESULT};
+    if (!Config->Entry.empty())
       addSyntheticUndefinedFunction(Config->Entry, &Signature);
-    }
 
     // Handle the `--undefined <sym>` options.
     for (StringRef S : args::getStrings(Args, OPT_undefined))
       addSyntheticUndefinedFunction(S, nullptr);
 
+    Config->CtorSymbol = Symtab->addDefinedFunction(
+        Config->CtorFunction, &Signature, WASM_SYMBOL_VISIBILITY_HIDDEN);
     Config->StackPointerSymbol = Symtab->addDefinedGlobal("__stack_pointer");
   }
 
Index: wasm/InputChunks.h
===================================================================
--- wasm/InputChunks.h
+++ wasm/InputChunks.h
@@ -50,7 +50,7 @@
   std::vector<OutputRelocation> OutRelocations;
 
 protected:
-  InputChunk(const ObjFile &F) : File(F) {}
+  InputChunk(const ObjFile *F) : File(F) {}
   virtual ~InputChunk() = default;
   void calcRelocations();
   virtual const uint8_t *getData() const = 0;
@@ -58,7 +58,7 @@
 
   std::vector<WasmRelocation> Relocations;
   int32_t OutputOffset = 0;
-  const ObjFile &File;
+  const ObjFile *File;
 };
 
 // Represents a WebAssembly data segment which can be included as part of
@@ -71,7 +71,7 @@
 // each global variable.
 class InputSegment : public InputChunk {
 public:
-  InputSegment(const WasmSegment &Seg, const ObjFile &F)
+  InputSegment(const WasmSegment &Seg, const ObjFile *F)
       : InputChunk(F), Segment(Seg) {}
 
   // Translate an offset in the input segment to an offset in the output
@@ -108,13 +108,13 @@
 // combined to create the final output CODE section.
 class InputFunction : public InputChunk {
 public:
-  InputFunction(const WasmSignature &S, const WasmFunction &Func,
-                const ObjFile &F)
+  InputFunction(const WasmSignature &S, const WasmFunction *Func,
+                const ObjFile *F)
       : InputChunk(F), Signature(S), Function(Func) {}
 
-  uint32_t getSize() const override { return Function.Size; }
+  uint32_t getSize() const override { return Function->Size; }
   const uint8_t *getData() const override {
-    return File.CodeSection->Content.data() + getInputSectionOffset();
+    return File->CodeSection->Content.data() + getInputSectionOffset();
   }
 
   uint32_t getOutputIndex() const { return OutputIndex.getValue(); };
@@ -128,12 +128,26 @@
 
 protected:
   uint32_t getInputSectionOffset() const override {
-    return Function.CodeSectionOffset;
+    return Function->CodeSectionOffset;
   }
-  const WasmFunction &Function;
+  const WasmFunction *Function;
   llvm::Optional<uint32_t> OutputIndex;
 };
 
+class SyntheticFunction : public InputFunction {
+public:
+  SyntheticFunction(const WasmSignature &S, StringRef Body)
+      : InputFunction(S, nullptr, nullptr), Body(Body) {}
+
+  uint32_t getSize() const override { return Body.size(); }
+  const uint8_t *getData() const override {
+    return reinterpret_cast<const uint8_t *>(Body.data());
+  }
+
+protected:
+  StringRef Body;
+};
+
 } // namespace wasm
 } // namespace lld
 
Index: wasm/InputChunks.cpp
===================================================================
--- wasm/InputChunks.cpp
+++ wasm/InputChunks.cpp
@@ -30,6 +30,8 @@
 }
 
 void InputChunk::copyRelocations(const WasmSection &Section) {
+  if (Section.Relocations.empty())
+    return;
   size_t Start = getInputSectionOffset();
   size_t Size = getSize();
   for (const WasmRelocation &R : Section.Relocations)
@@ -92,8 +94,10 @@
 // output section.  Calculates the updated index and offset for each relocation
 // as well as the value to write out in the final binary.
 void InputChunk::calcRelocations() {
+  if (Relocations.empty())
+    return;
   int32_t Off = getOutputOffset() - getInputSectionOffset();
-  log("calcRelocations: " + File.getName() + " offset=" + Twine(Off));
+  log("calcRelocations: " + File->getName() + " offset=" + Twine(Off));
   for (const WasmRelocation &Reloc : Relocations) {
     OutputRelocation NewReloc;
     NewReloc.Reloc = Reloc;
@@ -104,16 +108,16 @@
                  << " newOffset=" << NewReloc.Reloc.Offset << "\n");
 
     if (Config->EmitRelocs)
-      NewReloc.NewIndex = File.calcNewIndex(Reloc);
+      NewReloc.NewIndex = File->calcNewIndex(Reloc);
 
     switch (Reloc.Type) {
     case R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
     case R_WEBASSEMBLY_MEMORY_ADDR_I32:
     case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
-      NewReloc.Value = File.getRelocatedAddress(Reloc.Index) + Reloc.Addend;
+      NewReloc.Value = File->getRelocatedAddress(Reloc.Index) + Reloc.Addend;
       break;
     default:
-      NewReloc.Value = File.calcNewIndex(Reloc);
+      NewReloc.Value = File->calcNewIndex(Reloc);
       break;
     }
 
Index: wasm/InputFiles.cpp
===================================================================
--- wasm/InputFiles.cpp
+++ wasm/InputFiles.cpp
@@ -188,7 +188,7 @@
   GlobalSymbols.resize(NumGlobalImports + WasmObj->globals().size());
 
   for (const WasmSegment &S : WasmObj->dataSegments()) {
-    InputSegment *Seg = make<InputSegment>(S, *this);
+    InputSegment *Seg = make<InputSegment>(S, this);
     Seg->copyRelocations(*DataSection);
     Segments.emplace_back(Seg);
   }
@@ -199,7 +199,7 @@
   for (size_t I = 0; I < Funcs.size(); ++I) {
     const WasmFunction &Func = Funcs[I];
     const WasmSignature &Sig = Types[FuncTypes[I]];
-    InputFunction *F = make<InputFunction>(Sig, Func, *this);
+    InputFunction *F = make<InputFunction>(Sig, &Func, this);
     F->copyRelocations(*CodeSection);
     Functions.emplace_back(F);
   }
Index: wasm/SymbolTable.h
===================================================================
--- wasm/SymbolTable.h
+++ wasm/SymbolTable.h
@@ -55,6 +55,8 @@
                        InputFile *F, const WasmSignature *Signature = nullptr);
   Symbol *addUndefinedFunction(StringRef Name, const WasmSignature *Type);
   Symbol *addDefinedGlobal(StringRef Name);
+  Symbol *addDefinedFunction(StringRef Name, const WasmSignature *Type,
+                             uint32_t Flags);
   void addLazy(ArchiveFile *F, const Archive::Symbol *Sym);
 
 private:
Index: wasm/SymbolTable.cpp
===================================================================
--- wasm/SymbolTable.cpp
+++ wasm/SymbolTable.cpp
@@ -119,6 +119,22 @@
         " in " + F.getName());
 }
 
+Symbol *SymbolTable::addDefinedFunction(StringRef Name,
+                                        const WasmSignature *Type,
+                                        uint32_t Flags) {
+  DEBUG(dbgs() << "addDefinedFunction: " << Name << "\n");
+  Symbol *S;
+  bool WasInserted;
+  std::tie(S, WasInserted) = insert(Name);
+  if (WasInserted) {
+    S->update(Symbol::DefinedFunctionKind, nullptr, Flags);
+    S->setFunctionType(Type);
+  } else if (!S->isFunction()) {
+    error("symbol type mismatch: " + Name);
+  }
+  return S;
+}
+
 Symbol *SymbolTable::addDefinedGlobal(StringRef Name) {
   DEBUG(dbgs() << "addDefinedGlobal: " << Name << "\n");
   Symbol *S;
Index: wasm/Writer.cpp
===================================================================
--- wasm/Writer.cpp
+++ wasm/Writer.cpp
@@ -68,7 +68,10 @@
 private:
   void openFile();
 
-  uint32_t getTypeIndex(const WasmSignature &Sig);
+  uint32_t lookupType(const WasmSignature &Sig);
+  uint32_t registerType(const WasmSignature &Sig);
+  void createCtorFunction();
+  void calculateInitFunctions();
   void assignIndexes();
   void calculateImports();
   void calculateOffsets();
@@ -78,7 +81,7 @@
   void createHeader();
   void createSections();
   SyntheticSection *createSyntheticSection(uint32_t Type,
-                                           std::string Name = "");
+                                           StringRef Name = "");
 
   // Builtin sections
   void createTypeSection();
@@ -113,12 +116,15 @@
   std::vector<const Symbol *> DefinedGlobals;
   std::vector<InputFunction *> DefinedFunctions;
   std::vector<const Symbol *> IndirectFunctions;
+  std::vector<WasmInitFunc> InitFunctions;
 
   // Elements that are used to construct the final output
   std::string Header;
   std::vector<OutputSection *> OutputSections;
 
   std::unique_ptr<FileOutputBuffer> Buffer;
+  std::unique_ptr<SyntheticFunction> CtorFunction;
+  std::string CtorFunctionBody;
 
   std::vector<OutputSegment *> Segments;
   llvm::SmallDenseMap<StringRef, OutputSegment *> SegmentMap;
@@ -154,8 +160,7 @@
     Import.Module = "env";
     Import.Field = Sym->getName();
     Import.Kind = WASM_EXTERNAL_FUNCTION;
-    assert(TypeIndices.count(Sym->getFunctionType()) > 0);
-    Import.SigIndex = TypeIndices.lookup(Sym->getFunctionType());
+    Import.SigIndex = lookupType(Sym->getFunctionType());
     writeImport(OS, Import);
   }
 
@@ -196,8 +201,9 @@
   raw_ostream &OS = Section->getStream();
 
   writeUleb128(OS, DefinedFunctions.size(), "function count");
-  for (const InputFunction *Func : DefinedFunctions)
-    writeUleb128(OS, TypeIndices.lookup(Func->Signature), "sig index");
+  for (const InputFunction *Func : DefinedFunctions) {
+    writeUleb128(OS, lookupType(Func->Signature), "sig index");
+  }
 }
 
 void Writer::createMemorySection() {
@@ -410,15 +416,6 @@
     SubSection.writeToStream(OS);
   }
 
-  std::vector<WasmInitFunc> InitFunctions;
-  for (ObjFile *File : Symtab->ObjectFiles) {
-    const WasmLinkingData &L = File->getWasmObj()->linkingData();
-    InitFunctions.reserve(InitFunctions.size() + L.InitFunctions.size());
-    for (const WasmInitFunc &F : L.InitFunctions)
-      InitFunctions.emplace_back(WasmInitFunc{
-          F.Priority, File->relocateFunctionIndex(F.FunctionIndex)});
-  }
-
   if (!InitFunctions.empty()) {
     SubSection SubSection(WASM_INIT_FUNCS);
     writeUleb128(SubSection.getStream(), InitFunctions.size(),
@@ -447,6 +444,13 @@
     }
   }
 
+  for (Symbol *S : Symtab->getSymbols()) {
+    if (S->isFunction() && !S->getFile() && !S->WrittenToNameSec) {
+      S->WrittenToNameSec = true;
+      Names.emplace_back(S);
+    }
+  }
+
   SyntheticSection *Section = createSyntheticSection(WASM_SEC_CUSTOM, "name");
 
   std::sort(Names.begin(), Names.end(), [](const Symbol *A, const Symbol *B) {
@@ -520,7 +524,7 @@
 }
 
 SyntheticSection *Writer::createSyntheticSection(uint32_t Type,
-                                                 std::string Name) {
+                                                 StringRef Name) {
   auto Sec = make<SyntheticSection>(Type, Name);
   log("createSection: " + toString(*Sec));
   OutputSections.push_back(Sec);
@@ -570,10 +574,19 @@
   }
 }
 
-uint32_t Writer::getTypeIndex(const WasmSignature &Sig) {
+uint32_t Writer::lookupType(const WasmSignature &Sig) {
+  if (TypeIndices.count(Sig) == 0)
+    error("type not found: " + toString(Sig));
+  assert(TypeIndices.count(Sig) > 0);
+  return TypeIndices.lookup(Sig);
+}
+
+uint32_t Writer::registerType(const WasmSignature &Sig) {
   auto Pair = TypeIndices.insert(std::make_pair(Sig, Types.size()));
-  if (Pair.second)
+  if (Pair.second) {
+    DEBUG(dbgs() << "type " << toString(Sig) << "\n");
     Types.push_back(&Sig);
+  }
   return Pair.first->second;
 }
 
@@ -581,13 +594,17 @@
   for (ObjFile *File : Symtab->ObjectFiles) {
     File->TypeMap.reserve(File->getWasmObj()->types().size());
     for (const WasmSignature &Sig : File->getWasmObj()->types())
-      File->TypeMap.push_back(getTypeIndex(Sig));
+      File->TypeMap.push_back(registerType(Sig));
   }
+
+  for (Symbol *Sym : Symtab->getSymbols())
+    if (Sym->isFunction())
+      registerType(Sym->getFunctionType());
 }
 
 void Writer::assignIndexes() {
-  uint32_t GlobalIndex = ImportedGlobals.size();
-  uint32_t FunctionIndex = ImportedFunctions.size();
+  uint32_t GlobalIndex = ImportedGlobals.size() + DefinedGlobals.size();
+  uint32_t FunctionIndex = ImportedFunctions.size() + DefinedFunctions.size();
 
   if (Config->StackPointerSymbol) {
     DefinedGlobals.emplace_back(Config->StackPointerSymbol);
@@ -666,6 +683,38 @@
   }
 }
 
+static const int OPCODE_CALL = 0x10;
+static const int OPCODE_END = 0xb;
+
+void Writer::createCtorFunction() {
+  uint32_t FunctionIndex = ImportedFunctions.size() + DefinedFunctions.size();
+  Config->CtorSymbol->setOutputIndex(FunctionIndex);
+
+  static WasmSignature Signature = {{}, WASM_TYPE_NORESULT};
+  raw_string_ostream OS(CtorFunctionBody);
+  writeUleb128(OS, 2 + (2 * InitFunctions.size()), "function size");
+  writeUleb128(OS, 0, "num locals");
+  for (const WasmInitFunc &F : InitFunctions) {
+    writeUleb128(OS, OPCODE_CALL, "END");
+    writeUleb128(OS, F.FunctionIndex, "function index");
+  }
+  writeUleb128(OS, OPCODE_END, "END");
+  OS.flush();
+  CtorFunction =
+      llvm::make_unique<SyntheticFunction>(Signature, CtorFunctionBody);
+  DefinedFunctions.emplace_back(CtorFunction.get());
+}
+
+void Writer::calculateInitFunctions() {
+  for (ObjFile *File : Symtab->ObjectFiles) {
+    const WasmLinkingData &L = File->getWasmObj()->linkingData();
+    InitFunctions.reserve(InitFunctions.size() + L.InitFunctions.size());
+    for (const WasmInitFunc &F : L.InitFunctions)
+      InitFunctions.emplace_back(WasmInitFunc{
+          F.Priority, File->relocateFunctionIndex(F.FunctionIndex)});
+  }
+}
+
 void Writer::run() {
   if (!Config->Relocatable)
     InitialTableOffset = 1;
@@ -676,6 +725,10 @@
   calculateImports();
   log("-- assignIndexes");
   assignIndexes();
+  log("-- calculateInitFunctions");
+  calculateInitFunctions();
+  if (!Config->Relocatable)
+    createCtorFunction();
 
   if (errorHandler().Verbose) {
     log("Defined Functions: " + Twine(DefinedFunctions.size()));