2 files changed, 17 insertions, 0 deletions
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 474c1e490e4..b024d36acc3 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -524,6 +524,12 @@ bool Sema::MergeTypeDefDecl(TypedefDecl *New, Decl *OldD) {
       return false;
   }
 
+  // __builtin_va_list gets redeclared in the built-in definitions
+  // buffer when using PCH. Don't complain about such redefinitions.
+  if (Context.getExternalSource() && 
+      strcmp(SourceMgr.getBufferName(New->getLocation()), "<built-in>") == 0)
+    return false;
+
   Diag(New->getLocation(), diag::err_redefinition) << New->getDeclName();
   Diag(Old->getLocation(), diag::note_previous_definition);
   return true;
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 0b11d9cf68c..cd825070054 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -878,6 +878,17 @@ Sema::LookupName(Scope *S, DeclarationName Name, LookupNameKind NameKind,
         // We have a single lookup result.
         return LookupResult::CreateLookupResult(Context, *I);
       }
+
+    /// If the context has an external AST source attached, look at
+    /// translation unit scope.
+    if (Context.getExternalSource()) {
+      DeclContext::lookup_iterator I, E;
+      for (llvm::tie(I, E) 
+             = Context.getTranslationUnitDecl()->lookup(Context, Name); 
+           I != E; ++I)
+        if (isAcceptableLookupResult(*I, NameKind, IDNS))
+          return LookupResult::CreateLookupResult(Context, I, E);
+    }
   } else {
     // Perform C++ unqualified name lookup.
     std::pair<bool, LookupResult> MaybeResult =