GCC主要数据结构之cpp_macro_arg

/* A macro argument in the cpp_token union.  */
struct GTY(()) cpp_macro_arg {
  /* Argument number.  */
  unsigned int arg_no;
  /* The original spelling of the macro argument token.  */
  cpp_hashnode *
    GTY ((nested_ptr (union tree_node,
  "%h ? CPP_HASHNODE (GCC_IDENT_TO_HT_IDENT (%h)) : NULL",
   "%h ? HT_IDENT_TO_GCC_IDENT (HT_NODE (%h)) : NULL")))
       spelling;
};