Fix undefined behavior in debug info emission: operator* on WeakVH returns a

reference, so &* on an empty WeakVH binds a reference to a dereferenced null
pointer. So don't do that; we have a perfectly good implicit conversion to
Value*.

llvm-svn: 162079

1 files changed, 24 insertions, 17 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index ad21d210090..11e0e31c861 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -94,8 +94,10 @@ llvm::DIDescriptor CGDebugInfo::getContextDescriptor(const Decl *Context) {
 
   llvm::DenseMap<const Decl *, llvm::WeakVH>::iterator
     I = RegionMap.find(Context);
-  if (I != RegionMap.end())
-    return llvm::DIDescriptor(dyn_cast_or_null<llvm::MDNode>(&*I->second));
+  if (I != RegionMap.end()) {
+    llvm::Value *V = I->second;
+    return llvm::DIDescriptor(dyn_cast_or_null<llvm::MDNode>(V));
+  }
 
   // Check namespace.
   if (const NamespaceDecl *NSDecl = dyn_cast<NamespaceDecl>(Context))
@@ -227,8 +229,8 @@ llvm::DIFile CGDebugInfo::getOrCreateFile(SourceLocation Loc) {
 
   if (it != DIFileCache.end()) {
     // Verify that the information still exists.
-    if (&*it->second)
-      return llvm::DIFile(cast<llvm::MDNode>(it->second));
+    if (llvm::Value *V = it->second)
+      return llvm::DIFile(cast<llvm::MDNode>(V));
   }
 
   llvm::DIFile F = DBuilder.createFile(PLoc.getFilename(), getCurrentDirname());
@@ -539,8 +541,10 @@ llvm::DIDescriptor CGDebugInfo::createContextChain(const Decl *Context) {
   // See if we already have the parent.
   llvm::DenseMap<const Decl *, llvm::WeakVH>::iterator
     I = RegionMap.find(Context);
-  if (I != RegionMap.end())
-    return llvm::DIDescriptor(dyn_cast_or_null<llvm::MDNode>(&*I->second));
+  if (I != RegionMap.end()) {
+    llvm::Value *V = I->second;
+    return llvm::DIDescriptor(dyn_cast_or_null<llvm::MDNode>(V));
+  }
   
   // Check namespace.
   if (const NamespaceDecl *NSDecl = dyn_cast<NamespaceDecl>(Context))
@@ -1674,8 +1678,8 @@ llvm::DIType CGDebugInfo::getTypeOrNull(QualType Ty) {
     TypeCache.find(Ty.getAsOpaquePtr());
   if (it != TypeCache.end()) {
     // Verify that the debug info still exists.
-    if (&*it->second)
-      return llvm::DIType(cast<llvm::MDNode>(it->second));
+    if (llvm::Value *V = it->second)
+      return llvm::DIType(cast<llvm::MDNode>(V));
   }
 
   return llvm::DIType();
@@ -1693,8 +1697,8 @@ llvm::DIType CGDebugInfo::getCompletedTypeOrNull(QualType Ty) {
     CompletedTypeCache.find(Ty.getAsOpaquePtr());
   if (it != CompletedTypeCache.end()) {
     // Verify that the debug info still exists.
-    if (&*it->second)
-      return llvm::DIType(cast<llvm::MDNode>(it->second));
+    if (llvm::Value *V = it->second)
+      return llvm::DIType(cast<llvm::MDNode>(V));
   }
 
   return llvm::DIType();
@@ -1956,7 +1960,8 @@ llvm::DISubprogram CGDebugInfo::getFunctionDeclaration(const Decl *D) {
   llvm::DenseMap<const FunctionDecl *, llvm::WeakVH>::iterator
     MI = SPCache.find(FD->getCanonicalDecl());
   if (MI != SPCache.end()) {
-    llvm::DISubprogram SP(dyn_cast_or_null<llvm::MDNode>(&*MI->second));
+    llvm::Value *V = MI->second;
+    llvm::DISubprogram SP(dyn_cast_or_null<llvm::MDNode>(V));
     if (SP.isSubprogram() && !llvm::DISubprogram(SP).isDefinition())
       return SP;
   }
@@ -1967,7 +1972,8 @@ llvm::DISubprogram CGDebugInfo::getFunctionDeclaration(const Decl *D) {
     llvm::DenseMap<const FunctionDecl *, llvm::WeakVH>::iterator
       MI = SPCache.find(NextFD->getCanonicalDecl());
     if (MI != SPCache.end()) {
-      llvm::DISubprogram SP(dyn_cast_or_null<llvm::MDNode>(&*MI->second));
+      llvm::Value *V = MI->second;
+      llvm::DISubprogram SP(dyn_cast_or_null<llvm::MDNode>(V));
       if (SP.isSubprogram() && !llvm::DISubprogram(SP).isDefinition())
         return SP;
     }
@@ -2027,7 +2033,8 @@ void CGDebugInfo::EmitFunctionStart(GlobalDecl GD, QualType FnType,
     llvm::DenseMap<const FunctionDecl *, llvm::WeakVH>::iterator
       FI = SPCache.find(FD->getCanonicalDecl());
     if (FI != SPCache.end()) {
-      llvm::DIDescriptor SP(dyn_cast_or_null<llvm::MDNode>(&*FI->second));
+      llvm::Value *V = FI->second;
+      llvm::DIDescriptor SP(dyn_cast_or_null<llvm::MDNode>(V));
       if (SP.isSubprogram() && llvm::DISubprogram(SP).isDefinition()) {
         llvm::MDNode *SPN = SP;
         LexicalBlockStack.push_back(SPN);
@@ -2715,15 +2722,15 @@ void CGDebugInfo::finalize(void) {
          = ReplaceMap.begin(), VE = ReplaceMap.end(); VI != VE; ++VI) {
     llvm::DIType Ty, RepTy;
     // Verify that the debug info still exists.
-    if (&*VI->second)
-      Ty = llvm::DIType(cast<llvm::MDNode>(VI->second));
+    if (llvm::Value *V = VI->second)
+      Ty = llvm::DIType(cast<llvm::MDNode>(V));
     
     llvm::DenseMap<void *, llvm::WeakVH>::iterator it =
       TypeCache.find(VI->first);
     if (it != TypeCache.end()) {
       // Verify that the debug info still exists.
-      if (&*it->second)
-        RepTy = llvm::DIType(cast<llvm::MDNode>(it->second));
+      if (llvm::Value *V = it->second)
+        RepTy = llvm::DIType(cast<llvm::MDNode>(V));
     }
     
     if (Ty.Verify() && Ty.isForwardDecl() && RepTy.Verify()) {