re PR c++/51813 (-fvisibility=hidden causes std::codecvt members to be undefined)

	PR c++/51813
	* decl2.c (constrain_visibility): Clear DECL_VISIBILITY_SPECIFIED
	when reducing the visibility.

From-SVN: r183156

gcc/cp/ChangeLog

 2012-01-13  Jason Merrill  <jason@redhat.com>
 
+	PR c++/51813
+	* decl2.c (constrain_visibility): Clear DECL_VISIBILITY_SPECIFIED
+	when reducing the visibility.
+
 	PR c++/51620
 	* class.c (build_vtbl_initializer): Use __cxa_deleted_virtual.
 

gcc/cp/decl2.c

@@ -1984,6 +1984,8 @@ constrain_visibility (tree decl, int visibility, bool tmpl)
 	   && (tmpl || !DECL_VISIBILITY_SPECIFIED (decl)))
     {
       DECL_VISIBILITY (decl) = (enum symbol_visibility) visibility;
+      /* This visibility was not specified.  */
+      DECL_VISIBILITY_SPECIFIED (decl) = false;
     }
 }
 

gcc/testsuite/ChangeLog

 2012-01-13  Jason Merrill  <jason@redhat.com>
 
+	PR c++/51813
+	* g++.dg/ext/visibility/template9.C: New.
+
 	PR c++/51620
 	* g++.dg/cpp0x/defaulted34.C: New.
 	* g++.dg/template/virtual3.C: New.

gcc/testsuite/g++.dg/ext/visibility/template9.C

+// PR c++/51813
+// { dg-options -fvisibility=hidden }
+// { dg-final { scan-assembler-not "hidden\\s+_ZN1N1fI1AEEvT" } }
+
+struct A { };
+namespace N __attribute((visibility("default"))) {
+  template <class T> void f(T) { }
+  extern template void f(A);
+}
+
+int main()
+{
+  N::f(A());
+}