Fix use-after-free when a C++ thread_local variable gets replaced (because its

type changes when the initializer is attached). Don't hold onto the
GlobalVariable*; recompute it from the VarDecl* instead.

llvm-svn: 254359

clang/lib/CodeGen/CGCXXABI.h

@@ -538,11 +538,9 @@ public:
   ///        thread_local variables, a list of functions to perform the
   ///        initialization.
   virtual void EmitThreadLocalInitFuncs(
-      CodeGenModule &CGM,
-      ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *>>
-          CXXThreadLocals,
+      CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
       ArrayRef<llvm::Function *> CXXThreadLocalInits,
-      ArrayRef<llvm::GlobalVariable *> CXXThreadLocalInitVars) = 0;
+      ArrayRef<const VarDecl *> CXXThreadLocalInitVars) = 0;
 
   // Determine if references to thread_local global variables can be made
   // directly or require access through a thread wrapper function.

clang/lib/CodeGen/CGDeclCXX.cpp

@@ -337,7 +337,7 @@ CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
     // FIXME: We only need to register one __cxa_thread_atexit function for the
     // entire TU.
     CXXThreadLocalInits.push_back(Fn);
-    CXXThreadLocalInitVars.push_back(Addr);
+    CXXThreadLocalInitVars.push_back(D);
   } else if (PerformInit && ISA) {
     EmitPointerToInitFunc(D, Addr, Fn, ISA);
   } else if (auto *IPA = D->getAttr<InitPriorityAttr>()) {

clang/lib/CodeGen/CodeGenModule.cpp

@@ -1986,7 +1986,7 @@ CodeGenModule::GetOrCreateLLVMGlobal(StringRef MangledName,
 
     if (D->getTLSKind()) {
       if (D->getTLSKind() == VarDecl::TLS_Dynamic)
-        CXXThreadLocals.push_back(std::make_pair(D, GV));
+        CXXThreadLocals.push_back(D);
       setTLSMode(GV, *D);
     }
 
@@ -2379,7 +2379,7 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
 
   if (D->getTLSKind() && !GV->isThreadLocal()) {
     if (D->getTLSKind() == VarDecl::TLS_Dynamic)
-      CXXThreadLocals.push_back(std::make_pair(D, GV));
+      CXXThreadLocals.push_back(D);
     setTLSMode(GV, *D);
   }
 

clang/lib/CodeGen/CodeGenModule.h

@@ -378,13 +378,12 @@ private:
   StaticExternCMap StaticExternCValues;
 
   /// \brief thread_local variables defined or used in this TU.
-  std::vector<std::pair<const VarDecl *, llvm::GlobalVariable *> >
-    CXXThreadLocals;
+  std::vector<const VarDecl *> CXXThreadLocals;
 
   /// \brief thread_local variables with initializers that need to run
   /// before any thread_local variable in this TU is odr-used.
   std::vector<llvm::Function *> CXXThreadLocalInits;
-  std::vector<llvm::GlobalVariable *> CXXThreadLocalInitVars;
+  std::vector<const VarDecl *> CXXThreadLocalInitVars;
 
   /// Global variables with initializers that need to run before main.
   std::vector<llvm::Function *> CXXGlobalInits;

clang/lib/CodeGen/ItaniumCXXABI.cpp

@@ -327,10 +327,9 @@ public:
                                                 llvm::Value *Val);
   void EmitThreadLocalInitFuncs(
       CodeGenModule &CGM,
-      ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *>>
-          CXXThreadLocals,
+      ArrayRef<const VarDecl *> CXXThreadLocals,
       ArrayRef<llvm::Function *> CXXThreadLocalInits,
-      ArrayRef<llvm::GlobalVariable *> CXXThreadLocalInitVars) override;
+      ArrayRef<const VarDecl *> CXXThreadLocalInitVars) override;
 
   bool usesThreadWrapperFunction() const override { return true; }
   LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF, const VarDecl *VD,
@@ -2200,10 +2199,9 @@ ItaniumCXXABI::getOrCreateThreadLocalWrapper(const VarDecl *VD,
 }
 
 void ItaniumCXXABI::EmitThreadLocalInitFuncs(
-    CodeGenModule &CGM,
-    ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *>>
-        CXXThreadLocals, ArrayRef<llvm::Function *> CXXThreadLocalInits,
-    ArrayRef<llvm::GlobalVariable *> CXXThreadLocalInitVars) {
+    CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
+    ArrayRef<llvm::Function *> CXXThreadLocalInits,
+    ArrayRef<const VarDecl *> CXXThreadLocalInitVars) {
   llvm::Function *InitFunc = nullptr;
   if (!CXXThreadLocalInits.empty()) {
     // Generate a guarded initialization function.
@@ -2226,9 +2224,9 @@ void ItaniumCXXABI::EmitThreadLocalInitFuncs(
         .GenerateCXXGlobalInitFunc(InitFunc, CXXThreadLocalInits,
                                    Address(Guard, GuardAlign));
   }
-  for (auto &I : CXXThreadLocals) {
-    const VarDecl *VD = I.first;
-    llvm::GlobalVariable *Var = I.second;
+  for (const VarDecl *VD : CXXThreadLocals) {
+    llvm::GlobalVariable *Var =
+        cast<llvm::GlobalVariable>(CGM.GetGlobalValue(CGM.getMangledName(VD)));
 
     // Some targets require that all access to thread local variables go through
     // the thread wrapper.  This means that we cannot attempt to create a thread
@@ -2305,9 +2303,7 @@ void ItaniumCXXABI::EmitThreadLocalInitFuncs(
 LValue ItaniumCXXABI::EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF,
                                                    const VarDecl *VD,
                                                    QualType LValType) {
-  QualType T = VD->getType();
-  llvm::Type *Ty = CGF.getTypes().ConvertTypeForMem(T);
-  llvm::Value *Val = CGF.CGM.GetAddrOfGlobalVar(VD, Ty);
+  llvm::Value *Val = CGF.CGM.GetAddrOfGlobalVar(VD);
   llvm::Function *Wrapper = getOrCreateThreadLocalWrapper(VD, Val);
 
   Val = CGF.Builder.CreateCall(Wrapper);

clang/lib/CodeGen/MicrosoftCXXABI.cpp

@@ -377,11 +377,9 @@ public:
                                        const ReturnAdjustment &RA) override;
 
   void EmitThreadLocalInitFuncs(
-      CodeGenModule &CGM,
-      ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *>>
-          CXXThreadLocals,
+      CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
       ArrayRef<llvm::Function *> CXXThreadLocalInits,
-      ArrayRef<llvm::GlobalVariable *> CXXThreadLocalInitVars) override;
+      ArrayRef<const VarDecl *> CXXThreadLocalInitVars) override;
 
   bool usesThreadWrapperFunction() const override { return false; }
   LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF, const VarDecl *VD,
@@ -2197,11 +2195,9 @@ void MicrosoftCXXABI::registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
 }
 
 void MicrosoftCXXABI::EmitThreadLocalInitFuncs(
-    CodeGenModule &CGM,
-    ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *>>
-        CXXThreadLocals,
+    CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
     ArrayRef<llvm::Function *> CXXThreadLocalInits,
-    ArrayRef<llvm::GlobalVariable *> CXXThreadLocalInitVars) {
+    ArrayRef<const VarDecl *> CXXThreadLocalInitVars) {
   // This will create a GV in the .CRT$XDU section.  It will point to our
   // initialization function.  The CRT will call all of these function
   // pointers at start-up time and, eventually, at thread-creation time.
@@ -2219,7 +2215,8 @@ void MicrosoftCXXABI::EmitThreadLocalInitFuncs(
 
   std::vector<llvm::Function *> NonComdatInits;
   for (size_t I = 0, E = CXXThreadLocalInitVars.size(); I != E; ++I) {
-    llvm::GlobalVariable *GV = CXXThreadLocalInitVars[I];
+    llvm::GlobalVariable *GV = cast<llvm::GlobalVariable>(
+        CGM.GetGlobalValue(CGM.getMangledName(CXXThreadLocalInitVars[I])));
     llvm::Function *F = CXXThreadLocalInits[I];
 
     // If the GV is already in a comdat group, then we have to join it.

clang/test/CodeGenCXX/cxx11-thread-local.cpp

@@ -20,6 +20,18 @@ struct U { static thread_local int m; };
 // DARWIN: @_ZN1U1mE = internal thread_local global i32 0
 thread_local int U::m = f();
 
+namespace MismatchedInitType {
+  // Check that we don't crash here when we're forced to create a new global
+  // variable (with a different type) when we add the initializer.
+  union U {
+    int a;
+    float f;
+    constexpr U() : f(0.0) {}
+  };
+  static thread_local U u;
+  void *p = &u;
+}
+
 template<typename T> struct V { static thread_local int m; };
 template<typename T> thread_local int V<T>::m = g();