Submitted by: Bill Wendling

- Added C99 reference to why "auto" and "register" cannot be used as a
  storage class specifier for file scoped variable declarations.

llvm-svn: 39557
diff --git a/clang/Sema/SemaDecl.cpp b/clang/Sema/SemaDecl.cpp
index 2963c8f..a30944b 100644
--- a/clang/Sema/SemaDecl.cpp
+++ b/clang/Sema/SemaDecl.cpp
@@ -331,7 +331,8 @@
           return 0;
         }
       }
-      // FIXME: Find C99 spec reference
+      // C99 6.9p2: The storage-class specifiers auto and register shall not
+      // appear in the declaration specifiers in an external declaration.
       if (SC == VarDecl::Auto || SC == VarDecl::Register) {
         Diag(D.getIdentifierLoc(), diag::err_typecheck_sclass_fscope,
              R.getAsString());