Index: llvm/trunk/include/llvm/Demangle/Utility.h
===================================================================
--- llvm/trunk/include/llvm/Demangle/Utility.h
+++ llvm/trunk/include/llvm/Demangle/Utility.h
@@ -70,22 +70,6 @@
     BufferCapacity = BufferCapacity_;
   }
 
-  /// Create an OutputStream from a buffer and a size.  If either of these are
-  /// null a buffer is allocated.
-  static OutputStream create(char *StartBuf, size_t *Size, size_t AllocSize) {
-    OutputStream Result;
-
-    if (!StartBuf || !Size) {
-      StartBuf = static_cast<char *>(std::malloc(AllocSize));
-      if (StartBuf == nullptr)
-        std::terminate();
-      Size = &AllocSize;
-    }
-
-    Result.reset(StartBuf, *Size);
-    return Result;
-  }
-
   /// If a ParameterPackExpansion (or similar type) is encountered, the offset
   /// into the pack that we're currently printing.
   unsigned CurrentPackIndex = std::numeric_limits<unsigned>::max();
@@ -185,4 +169,19 @@
   SwapAndRestore &operator=(const SwapAndRestore &) = delete;
 };
 
+inline bool initializeOutputStream(char *Buf, size_t *N, OutputStream &S,
+                                   size_t InitSize) {
+  size_t BufferSize;
+  if (Buf == nullptr) {
+    Buf = static_cast<char *>(std::malloc(InitSize));
+    if (Buf == nullptr)
+      return true;
+    BufferSize = InitSize;
+  } else
+    BufferSize = *N;
+
+  S.reset(Buf, BufferSize);
+  return false;
+}
+
 #endif
Index: llvm/trunk/lib/Demangle/ItaniumDemangle.cpp
===================================================================
--- llvm/trunk/lib/Demangle/ItaniumDemangle.cpp
+++ llvm/trunk/lib/Demangle/ItaniumDemangle.cpp
@@ -310,21 +310,6 @@
     return Alloc.allocate(sizeof(Node *) * sz);
   }
 };
-
-bool initializeOutputStream(char *Buf, size_t *N, OutputStream &S,
-                            size_t InitSize) {
-  size_t BufferSize;
-  if (Buf == nullptr) {
-    Buf = static_cast<char *>(std::malloc(InitSize));
-    if (Buf == nullptr)
-      return true;
-    BufferSize = InitSize;
-  } else
-    BufferSize = *N;
-
-  S.reset(Buf, BufferSize);
-  return false;
-}
 }  // unnamed namespace
 
 //===----------------------------------------------------------------------===//
Index: llvm/trunk/lib/Demangle/MicrosoftDemangle.cpp
===================================================================
--- llvm/trunk/lib/Demangle/MicrosoftDemangle.cpp
+++ llvm/trunk/lib/Demangle/MicrosoftDemangle.cpp
@@ -1016,7 +1016,10 @@
 void Demangler::memorizeIdentifier(IdentifierNode *Identifier) {
   // Render this class template name into a string buffer so that we can
   // memorize it for the purpose of back-referencing.
-  OutputStream OS = OutputStream::create(nullptr, nullptr, 1024);
+  OutputStream OS;
+  if (initializeOutputStream(nullptr, nullptr, OS, 1024))
+    // FIXME: Propagate out-of-memory as an error?
+    std::terminate();
   Identifier->output(OS, OF_Default);
   OS << '\0';
   char *Name = OS.getBuffer();
@@ -1346,7 +1349,9 @@
   if (MangledName.empty())
     goto StringLiteralError;
 
-  OS = OutputStream::create(nullptr, nullptr, 1024);
+  if (initializeOutputStream(nullptr, nullptr, OS, 1024))
+    // FIXME: Propagate out-of-memory as an error?
+    std::terminate();
   if (IsWcharT) {
     Result->Char = CharKind::Wchar;
     if (StringByteSize > 64)
@@ -1466,7 +1471,10 @@
     return nullptr;
 
   // Render the parent symbol's name into a buffer.
-  OutputStream OS = OutputStream::create(nullptr, nullptr, 1024);
+  OutputStream OS;
+  if (initializeOutputStream(nullptr, nullptr, OS, 1024))
+    // FIXME: Propagate out-of-memory as an error?
+    std::terminate();
   OS << '`';
   Scope->output(OS, OF_Default);
   OS << '\'';
@@ -2289,7 +2297,9 @@
               (int)Backrefs.FunctionParamCount);
 
   // Create an output stream so we can render each type.
-  OutputStream OS = OutputStream::create(nullptr, 0, 1024);
+  OutputStream OS;
+  if (initializeOutputStream(nullptr, nullptr, OS, 1024))
+    std::terminate();
   for (size_t I = 0; I < Backrefs.FunctionParamCount; ++I) {
     OS.setCurrentPosition(0);
 
@@ -2314,21 +2324,29 @@
 
 char *llvm::microsoftDemangle(const char *MangledName, char *Buf, size_t *N,
                               int *Status, MSDemangleFlags Flags) {
+  int InternalStatus = demangle_success;
   Demangler D;
+  OutputStream S;
+
   StringView Name{MangledName};
-  SymbolNode *S = D.parse(Name);
+  SymbolNode *AST = D.parse(Name);
 
   if (Flags & MSDF_DumpBackrefs)
     D.dumpBackReferences();
-  OutputStream OS = OutputStream::create(Buf, N, 1024);
-  if (D.Error) {
-    OS << MangledName;
-    *Status = llvm::demangle_invalid_mangled_name;
-  } else {
-    S->output(OS, OF_Default);
-    *Status = llvm::demangle_success;
+
+  if (D.Error)
+    InternalStatus = demangle_invalid_mangled_name;
+  else if (initializeOutputStream(Buf, N, S, 1024))
+    InternalStatus = demangle_memory_alloc_failure;
+  else {
+    AST->output(S, OF_Default);
+    S += '\0';
+    if (N != nullptr)
+      *N = S.getCurrentPosition();
+    Buf = S.getBuffer();
   }
 
-  OS << '\0';
-  return OS.getBuffer();
+  if (Status)
+    *Status = InternalStatus;
+  return InternalStatus == demangle_success ? Buf : nullptr;
 }