this is a gcc file, you can download it and learn its usetility, for further detail please look at t

				// Distillation of crash1.C problem (PR 3633)				// Build don't link:								template				class A				{				  P p;				};								template				class B				{				  A a;			// bogus error - temp parm name propagating				};								template				class C				{				  B b;				};								template				class D				{				  S s;				};								C< D > c;