用于进行gcc测试

				// { dg-do compile }								// Copyright (C) 2004 Free Software Foundation, Inc.				// Contributed by Nathan Sidwell 24 Aug 2004 				// Origin: Wolfgang Bangerth  								// Bug 16889:Undetected ambiguity.								struct B { 				  int f(); // { dg-error "int B::f" "" }				}; 				 				struct B1 : virtual B {}; 				struct B2 : B {}; 				struct BB : B1, B2 {}; 				 				int i = BB().f();  // { dg-error "ambiguous" "" }