Fix build error.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@69009 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/AST/ExternalASTSource.h b/include/clang/AST/ExternalASTSource.h
index 54fe3639ad0d2baf79acd9c65694a851a6d5fac5..2ec29d80ec04f0461ff614d730afb2207d3ffc2e 100644 (file)
--- a/include/clang/AST/ExternalASTSource.h
+++ b/include/clang/AST/ExternalASTSource.h
@@ -86,7 +86,7 @@ public:
 
   /// \brief Function that will be invoked when we begin parsing a new
   /// translation unit involving this external AST source.
-  virtual void StartTranslationUnit(ASTConsumer *Consumer);
+  virtual void StartTranslationUnit(ASTConsumer *Consumer) { }
 
   /// \brief Print any statistics that have been gathered regarding
   /// the external AST source.