1 files changed, 37 insertions, 18 deletions

diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index 0c03201aa6d..1458a73a7d3 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -149,6 +149,24 @@ static StringRef sanitizeFilenameAsIdentifier(StringRef Name,
   return Name;
 }
 
+/// \brief Determine whether the given file name is the name of a builtin
+/// header, supplied by Clang to replace, override, or augment existing system
+/// headers.
+static bool isBuiltinHeader(StringRef FileName) {
+  return llvm::StringSwitch<bool>(FileName)
+           .Case("float.h", true)
+           .Case("iso646.h", true)
+           .Case("limits.h", true)
+           .Case("stdalign.h", true)
+           .Case("stdarg.h", true)
+           .Case("stdbool.h", true)
+           .Case("stddef.h", true)
+           .Case("stdint.h", true)
+           .Case("tgmath.h", true)
+           .Case("unwind.h", true)
+           .Default(false);
+}
+
 Module *ModuleMap::findModuleForHeader(const FileEntry *File) {
   HeadersMap::iterator Known = Headers.find(File);
   if (Known != Headers.end()) {
@@ -158,6 +176,25 @@ Module *ModuleMap::findModuleForHeader(const FileEntry *File) {
 
     return Known->second.getModule();
   }
+
+  // If we've found a builtin header within Clang's builtin include directory,
+  // load all of the module maps to see if it will get associated with a
+  // specific module (e.g., in /usr/include).
+  if (File->getDir() == BuiltinIncludeDir &&
+      isBuiltinHeader(llvm::sys::path::filename(File->getName()))) {
+    SmallVector<Module *, 4> AllModules;
+    HeaderInfo.collectAllModules(AllModules);
+
+    // Check again.
+    Known = Headers.find(File);
+    if (Known != Headers.end()) {
+      // If a header is not available, don't report that it maps to anything.
+      if (!Known->second.isAvailable())
+        return 0;
+
+      return Known->second.getModule();
+    }
+  }
   
   const DirectoryEntry *Dir = File->getDir();
   SmallVector<const DirectoryEntry *, 2> SkippedDirs;
@@ -1266,24 +1303,6 @@ static void appendSubframeworkPaths(Module *Mod,
   }
 }
 
-/// \brief Determine whether the given file name is the name of a builtin
-/// header, supplied by Clang to replace, override, or augment existing system
-/// headers.
-static bool isBuiltinHeader(StringRef FileName) {
-  return llvm::StringSwitch<bool>(FileName)
-      .Case("float.h", true)
-      .Case("iso646.h", true)
-      .Case("limits.h", true)
-      .Case("stdalign.h", true)
-      .Case("stdarg.h", true)
-      .Case("stdbool.h", true)
-      .Case("stddef.h", true)
-      .Case("stdint.h", true)
-      .Case("tgmath.h", true)
-      .Case("unwind.h", true)
-      .Default(false);
-}
-
 /// \brief Parse a header declaration.
 ///
 ///   header-declaration: