re PR c/46889 (Missing diagnosis on duplicate struct member with anonymous union)

PR c/46889
	* c-decl.c (detect_field_duplicates): Ensure hash is used for
	finding duplicates when first field is anonymous.

testsuite:
	* gcc.dg/anon-struct-15.c: New test.

From-SVN: r168348

gcc/ChangeLog

@@ -1,3 +1,9 @@
+2010-12-30  Joseph Myers  <joseph@codesourcery.com>
+
+	PR c/46889
+	* c-decl.c (detect_field_duplicates): Ensure hash is used for
+	finding duplicates when first field is anonymous.
+
 2010-12-30  Nathan Froyd  <froydnj@codesourcery.com>
 
         PR target/44606

gcc/c-decl.c

@@ -6805,11 +6805,9 @@ detect_field_duplicates (tree fieldlist)
 
   /* First, see if there are more than "a few" fields.
      This is trivially true if there are zero or one fields.  */
-  if (!fieldlist)
+  if (!fieldlist || !DECL_CHAIN (fieldlist))
-    return;
-  x = DECL_CHAIN (fieldlist);
-  if (!x)
     return;
+  x = fieldlist;
   do {
     timeout--;
     if (DECL_NAME (x) == NULL_TREE

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2010-12-30  Joseph Myers  <joseph@codesourcery.com>
+
+	PR c/46889
+	* gcc.dg/anon-struct-15.c: New test.
+
 2010-12-30  Nathan Froyd  <froydnj@codesourcery.com>
 
         PR target/44606

gcc/testsuite/gcc.dg/anon-struct-15.c

@@ -0,0 +1,16 @@
+/* Test diagnostics for duplicate field names involving anonymous
+   struct or union as first field.  PR 46889.  */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+struct foo {
+  union {
+    struct {
+      unsigned long time_stamp;
+    };
+    struct {
+      int *page;
+    };
+  };
+  int *page; /* { dg-error "duplicate member" } */
+};