Index: lldb/trunk/include/lldb/Utility/ConstString.h
===================================================================
--- lldb/trunk/include/lldb/Utility/ConstString.h
+++ lldb/trunk/include/lldb/Utility/ConstString.h
@@ -346,6 +346,15 @@
   bool IsEmpty() const { return m_string == nullptr || m_string[0] == '\0'; }
 
   //------------------------------------------------------------------
+  /// Test for null string.
+  ///
+  /// @return
+  ///     @li \b true if there is no string associated with this instance.
+  ///     @li \b false if there is a string associated with this instance.
+  //------------------------------------------------------------------
+  bool IsNull() const { return m_string == nullptr; }
+
+  //------------------------------------------------------------------
   /// Set the C string value.
   ///
   /// Set the string value in the object by uniquing the \a cstr string value
Index: lldb/trunk/source/Core/Mangled.cpp
===================================================================
--- lldb/trunk/source/Core/Mangled.cpp
+++ lldb/trunk/source/Core/Mangled.cpp
@@ -242,7 +242,7 @@
 Mangled::GetDemangledName(lldb::LanguageType language) const {
   // Check to make sure we have a valid mangled name and that we haven't
   // already decoded our mangled name.
-  if (m_mangled && !m_demangled) {
+  if (m_mangled && m_demangled.IsNull()) {
     // We need to generate and cache the demangled name.
     static Timer::Category func_cat(LLVM_PRETTY_FUNCTION);
     Timer scoped_timer(func_cat, "Mangled::GetDemangledName (m_mangled = %s)",
@@ -312,7 +312,7 @@
         free(demangled_name);
       }
     }
-    if (!m_demangled) {
+    if (m_demangled.IsNull()) {
       // Set the demangled string to the empty string to indicate we tried to
       // parse it once and failed.
       m_demangled.SetCString("");
Index: lldb/trunk/unittests/Utility/ConstStringTest.cpp
===================================================================
--- lldb/trunk/unittests/Utility/ConstStringTest.cpp
+++ lldb/trunk/unittests/Utility/ConstStringTest.cpp
@@ -33,3 +33,20 @@
   EXPECT_TRUE(foo.GetMangledCounterpart(counterpart));
   EXPECT_EQ("bar", counterpart.GetStringRef());
 }
+
+TEST(ConstStringTest, NullAndEmptyStates) {
+  ConstString foo("foo");
+  EXPECT_FALSE(!foo);
+  EXPECT_FALSE(foo.IsEmpty());
+  EXPECT_FALSE(foo.IsNull());
+
+  ConstString empty("");
+  EXPECT_TRUE(!empty);
+  EXPECT_TRUE(empty.IsEmpty());
+  EXPECT_FALSE(empty.IsNull());
+
+  ConstString null;
+  EXPECT_TRUE(!null);
+  EXPECT_TRUE(null.IsEmpty());
+  EXPECT_TRUE(null.IsNull());
+}