Index: gcc/c/ChangeLog
===================================================================
--- gcc/c/ChangeLog	(revision 229395)
+++ gcc/c/ChangeLog	(working copy)
@@ -1,3 +1,9 @@
+2015-10-26  Jim Wilson  <jim.wilson@linaro.org>
+
+	PR debug/66068
+	* c-typeck.c (c_build_qualified_type): Clear C_TYPE_INCOMPLETE_VARS
+	after calling build_qualified_type.
+
 2015-10-22  Richard Biener  <rguenther@suse.de>
 
 	* c-typeck.c (c_finish_omp_clauses): Properly convert operands
Index: gcc/c/c-typeck.c
===================================================================
--- gcc/c/c-typeck.c	(revision 229395)
+++ gcc/c/c-typeck.c	(working copy)
@@ -13090,6 +13090,8 @@ c_finish_transaction (location_t loc, tree block,
 tree
 c_build_qualified_type (tree type, int type_quals)
 {
+  tree var_type;
+
   if (type == error_mark_node)
     return type;
 
@@ -13146,7 +13148,13 @@ c_build_qualified_type (tree type, int type_quals)
       type_quals &= ~TYPE_QUAL_RESTRICT;
     }
 
-  return build_qualified_type (type, type_quals);
+  var_type = build_qualified_type (type, type_quals);
+  /* A variant type does not inherit the list of incomplete vars from the
+     type main variant.  */
+  if (TREE_CODE (var_type) == RECORD_TYPE
+      || TREE_CODE (var_type) == UNION_TYPE)
+    C_TYPE_INCOMPLETE_VARS (var_type) = 0;
+  return var_type;
 }
 
 /* Build a VA_ARG_EXPR for the C parser.  */
Index: gcc/testsuite/ChangeLog
===================================================================
--- gcc/testsuite/ChangeLog	(revision 229395)
+++ gcc/testsuite/ChangeLog	(working copy)
@@ -1,3 +1,8 @@
+2015-10-26  Jim Wilson  <jim.wilson@linaro.org>
+
+	PR debug/66068
+	* gcc.dg/debug/pr66068.c: New test.
+
 2015-10-26  Louis Krupp  <louis.krupp@zoho.com>
 
 	PR fortran/66056
Index: gcc/testsuite/gcc.dg/debug/pr66068.c
===================================================================
--- gcc/testsuite/gcc.dg/debug/pr66068.c	(revision 0)
+++ gcc/testsuite/gcc.dg/debug/pr66068.c	(working copy)
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+
+struct S a;
+const struct S b;
+struct S
+{
+};
+
+union U c;
+const union U d;
+union U
+{
+};