diff --git a/lib/Basic/Module.cpp b/lib/Basic/Module.cpp
index c0f5a6a..e7e37ce 100644
--- a/lib/Basic/Module.cpp
+++ b/lib/Basic/Module.cpp
@@ -26,7 +26,7 @@
 
 Module::Module(StringRef Name, SourceLocation DefinitionLoc, Module *Parent,
                bool IsFramework, bool IsExplicit)
-    : Name(Name), DefinitionLoc(DefinitionLoc), Parent(Parent),
+    : Name(Name), DefinitionLoc(DefinitionLoc), Parent(Parent), Directory(),
       Umbrella(), ASTFile(nullptr), IsMissingRequirement(false),
       IsAvailable(true), IsFromModuleFile(false), IsFramework(IsFramework),
       IsExplicit(IsExplicit), IsSystem(false), IsExternC(false),
@@ -58,21 +58,26 @@
 /// language options has the given feature.
 static bool hasFeature(StringRef Feature, const LangOptions &LangOpts,
                        const TargetInfo &Target) {
-  return llvm::StringSwitch<bool>(Feature)
-           .Case("altivec", LangOpts.AltiVec)
-           .Case("blocks", LangOpts.Blocks)
-           .Case("cplusplus", LangOpts.CPlusPlus)
-           .Case("cplusplus11", LangOpts.CPlusPlus11)
-           .Case("objc", LangOpts.ObjC1)
-           .Case("objc_arc", LangOpts.ObjCAutoRefCount)
-           .Case("opencl", LangOpts.OpenCL)
-           .Case("tls", Target.isTLSSupported())
-           .Default(Target.hasFeature(Feature));
+  bool HasFeature = llvm::StringSwitch<bool>(Feature)
+                        .Case("altivec", LangOpts.AltiVec)
+                        .Case("blocks", LangOpts.Blocks)
+                        .Case("cplusplus", LangOpts.CPlusPlus)
+                        .Case("cplusplus11", LangOpts.CPlusPlus11)
+                        .Case("objc", LangOpts.ObjC1)
+                        .Case("objc_arc", LangOpts.ObjCAutoRefCount)
+                        .Case("opencl", LangOpts.OpenCL)
+                        .Case("tls", Target.isTLSSupported())
+                        .Default(Target.hasFeature(Feature));
+  if (!HasFeature)
+    HasFeature = std::find(LangOpts.ModuleFeatures.begin(),
+                           LangOpts.ModuleFeatures.end(),
+                           Feature) != LangOpts.ModuleFeatures.end();
+  return HasFeature;
 }
 
-bool
-Module::isAvailable(const LangOptions &LangOpts, const TargetInfo &Target,
-                    Requirement &Req, HeaderDirective &MissingHeader) const {
+bool Module::isAvailable(const LangOptions &LangOpts, const TargetInfo &Target,
+                         Requirement &Req,
+                         UnresolvedHeaderDirective &MissingHeader) const {
   if (IsAvailable)
     return true;
 
@@ -293,9 +298,12 @@
     OS << "explicit ";
   OS << "module " << Name;
 
-  if (IsSystem) {
+  if (IsSystem || IsExternC) {
     OS.indent(Indent + 2);
-    OS << " [system]";
+    if (IsSystem)
+      OS << " [system]";
+    if (IsExternC)
+      OS << " [extern_c]";
   }
 
   OS << " {\n";
@@ -338,19 +346,20 @@
     OS << "\n";
   }
 
-  struct HeaderKind {
+  struct {
     StringRef Prefix;
-    const SmallVectorImpl<const FileEntry *> &Headers;
-  } Kinds[] = {{"", NormalHeaders},
-               {"exclude ", ExcludedHeaders},
-               {"textual ", TextualHeaders},
-               {"private ", PrivateHeaders}};
+    HeaderKind Kind;
+  } Kinds[] = {{"", HK_Normal},
+               {"textual ", HK_Textual},
+               {"private ", HK_Private},
+               {"private textual ", HK_PrivateTextual},
+               {"exclude ", HK_Excluded}};
 
   for (auto &K : Kinds) {
-    for (auto *H : K.Headers) {
+    for (auto &H : Headers[K.Kind]) {
       OS.indent(Indent + 2);
       OS << K.Prefix << "header \"";
-      OS.write_escaped(H->getName());
+      OS.write_escaped(H.NameAsWritten);
       OS << "\"\n";
     }
   }