From 8644c890f457ece8942c9cf51016737b5cedf79d Mon Sep 17 00:00:00 2001
From: Frederich Munch <marsupial@users.noreply.github.com>
Date: Tue, 20 Sep 2016 23:53:57 -0400
Subject: [PATCH] Windows: Fix crash on unloading of Dtor_Comdat destructors.

---
 lib/Interpreter/DeclUnloader.cpp | 44 +++++++++++++++++++++-----------
 lib/Interpreter/DeclUnloader.h   |  3 ++-
 2 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/lib/Interpreter/DeclUnloader.cpp b/lib/Interpreter/DeclUnloader.cpp
index 35fb1c6b..9417cb36 100644
--- a/lib/Interpreter/DeclUnloader.cpp
+++ b/lib/Interpreter/DeclUnloader.cpp
@@ -649,7 +649,12 @@ bool DeclUnloader::VisitRedeclarable(clang::Redeclarable<T>* R, DeclContext* DC)
     GD = GlobalDecl(CXXDtor, Dtor_Base);
     MaybeRemoveDeclFromModule(GD);
     GD = GlobalDecl(CXXDtor, Dtor_Comdat);
+#if defined(LLVM_ON_WIN32)
+    // MicrosoftMangle.cpp:954 calls llvm_unreachable when mangling Dtor_Comdat
+    MaybeRemoveDeclFromModule(GD, false);
+#else
     MaybeRemoveDeclFromModule(GD);
+#endif
 
     bool Successful = VisitCXXMethodDecl(CXXDtor);
     return Successful;
@@ -729,7 +734,8 @@ bool DeclUnloader::VisitRedeclarable(clang::Redeclarable<T>* R, DeclContext* DC)
     return Successful;
   }
 
-  void DeclUnloader::MaybeRemoveDeclFromModule(GlobalDecl& GD) const {
+  void DeclUnloader::MaybeRemoveDeclFromModule(GlobalDecl& GD,
+                                               bool Mangle) const {
     if (!m_CurTransaction
         || !m_CurTransaction->getModule()) // syntax-only mode exit
       return;
@@ -772,23 +778,31 @@ bool DeclUnloader::VisitRedeclarable(clang::Redeclarable<T>* R, DeclContext* DC)
     //
     if (m_CurTransaction->getState() == Transaction::kCommitted) {
       std::string mangledName;
-      utils::Analyze::maybeMangleDeclName(GD, mangledName);
+      if (LLVM_UNLIKELY(!Mangle)) {
+        const NamedDecl* D = cast<NamedDecl>(const_cast<Decl*>(GD.getDecl()));
+        if (const IdentifierInfo *II = D->getIdentifier())
+          mangledName = II->getName();
+      } else
+        utils::Analyze::maybeMangleDeclName(GD, mangledName);
 
-      // Handle static locals. void func() { static int var; } is represented in
-      // the llvm::Module is a global named @func.var
-      if (const VarDecl* VD = dyn_cast<VarDecl>(GD.getDecl()))
-        if (VD->isStaticLocal()) {
-          std::string functionMangledName;
-          GlobalDecl FDGD(cast<FunctionDecl>(VD->getDeclContext()));
-          utils::Analyze::maybeMangleDeclName(FDGD, functionMangledName);
-          mangledName = functionMangledName + "." + mangledName;
+      if (LLVM_LIKELY(!mangledName.empty())) {
+        // Handle static locals. void func() { static int var; } is represented
+        // in the llvm::Module is a global named @func.var
+        if (const VarDecl* VD = dyn_cast<VarDecl>(GD.getDecl())) {
+          if (VD->isStaticLocal()) {
+            std::string functionMangledName;
+            GlobalDecl FDGD(cast<FunctionDecl>(VD->getDeclContext()));
+            utils::Analyze::maybeMangleDeclName(FDGD, functionMangledName);
+            mangledName = functionMangledName + "." + mangledName;
+          }
         }
 
-      llvm::Module* M = m_CurTransaction->getModule();
-      GlobalValue* GV = M->getNamedValue(mangledName);
-      if (GV) { // May be deferred decl and thus 0
-        GlobalValueEraser GVEraser(m_CodeGen);
-        GVEraser.EraseGlobalValue(GV);
+        llvm::Module* M = m_CurTransaction->getModule();
+        GlobalValue* GV = M->getNamedValue(mangledName);
+        if (GV) { // May be deferred decl and thus 0
+          GlobalValueEraser GVEraser(m_CodeGen);
+          GVEraser.EraseGlobalValue(GV);
+        }
       }
       m_CodeGen->forgetDecl(GD);
     }
diff --git a/lib/Interpreter/DeclUnloader.h b/lib/Interpreter/DeclUnloader.h
index f4a3cde3..2372ecc8 100644
--- a/lib/Interpreter/DeclUnloader.h
+++ b/lib/Interpreter/DeclUnloader.h
@@ -228,7 +228,8 @@ namespace cling {
 
     ///@}
 
-    void MaybeRemoveDeclFromModule(clang::GlobalDecl& GD) const;
+    void MaybeRemoveDeclFromModule(clang::GlobalDecl& GD,
+                                   bool Mangle = true) const;
 
     /// @name Helpers
     /// @{