2007-11-22  Jakub Jelinek  <jakub@redhat.com>

	PR c++/34094
	* decl2.c (cp_write_global_declarations): Issue error about static
	data members in anonymous namespace which are declared and used,
	but not defined.

	* g++.dg/ext/visibility/anon7.C: New test.

--- gcc/cp/decl2.c	(revision 130350)
+++ gcc/cp/decl2.c	(revision 130351)
@@ -3365,7 +3365,21 @@ cp_write_global_declarations (void)
 	  /* If this static data member is needed, provide it to the
 	     back end.  */
 	  if (DECL_NOT_REALLY_EXTERN (decl) && decl_needed_p (decl))
-	    DECL_EXTERNAL (decl) = 0;
+	    {
+	      /* Error on
+		 namespace { struct A { static int i; }; }
+		 int foo () { return A::i; }
+		 without A::i definition (which can't be defined in
+		 a different CU because of the anonymous namespace).
+		 Don't do this if DECL_INITIAL is set, because for
+		 namespace { struct A { static const int i = 4; } };
+		 decl_needed_p won't reliably detect whether it was
+		 really needed.  */
+	      if (DECL_IN_AGGR_P (decl) && DECL_INITIAL (decl) == NULL_TREE)
+		error ("%Jstatic data member %qD used, but not defined",
+		       decl, decl);
+	      DECL_EXTERNAL (decl) = 0;
+	    }
 	}
       if (VEC_length (tree, pending_statics) != 0
 	  && wrapup_global_declarations (VEC_address (tree, pending_statics),
--- gcc/testsuite/g++.dg/ext/visibility/anon7.C	(revision 0)
+++ gcc/testsuite/g++.dg/ext/visibility/anon7.C	(revision 130351)
@@ -0,0 +1,23 @@
+// PR c++/34094
+// { dg-do compile }
+
+namespace
+{
+  struct A {
+    static int bar ();
+    static int i;		// { dg-error "used, but not defined" }
+    static int j;
+    static int k;
+    static int l;
+    static const int m = 16;
+    static const int n = 17;
+  };
+  int A::j = 4;
+  int A::k;
+  const int A::m;
+}
+
+int foo (void)
+{
+  return A::i + A::j + A::k + A::m + A::n + A::bar ();
+}