1 struct tree_decl 2 { 3 unsigned in_system_header_flag:1; 4 }; 5 union tree_node 6 { 7 struct tree_decl decl; 8 }; 9 typedef union tree_node *tree; 10 static int redeclaration_error_message(olddecl)11redeclaration_error_message (olddecl) 12 tree olddecl; 13 { 14 if (({olddecl;})->decl.in_system_header_flag) 15 ; 16 } 17