GCC主要数据结构之cpp_hashnode

#define CPP_HASHNODE_VALUE_IDX(HNODE)    \
  ((HNODE.flags & NODE_MACRO_ARG) ? NTV_ARGUMENT  \
   : HNODE.type == NT_MACRO ? ((HNODE.flags & NODE_BUILTIN)  \
          ? NTV_BUILTIN : NTV_MACRO) \
   : HNODE.type == NT_ASSERTION ? NTV_ANSWER   \
   : NTV_NONE)
/* The common part of an identifier node shared amongst all 3 C front
   ends.  Also used to store CPP identifiers, which are a superset of
   identifiers in the grammatical sense.  */
union GTY(()) _cpp_hashnode_value {
  /* If a macro.  */
  cpp_macro * GTY((tag ("NTV_MACRO"))) macro;
  /* Answers to an assertion.  */
  struct answer * GTY ((tag ("NTV_ANSWER"))) answers;
  /* Code for a builtin macro.  */
  enum cpp_builtin_type GTY ((tag ("NTV_BUILTIN"))) builtin;
  /* Macro argument index.  */
  unsigned short GTY ((tag ("NTV_ARGUMENT"))) arg_index;
};
struct GTY(()) cpp_hashnode {
  struct ht_identifier ident;
  unsigned int is_directive : 1;
  unsigned int directive_index : 7; /* If is_directive,
        then index into directive table.
        Otherwise, a NODE_OPERATOR.  */
  unsigned char rid_code;  /* Rid code - for front ends.  */
  ENUM_BITFIELD(node_type) type : 6; /* CPP node type.  */
  unsigned int flags : 10;  /* CPP flags.  */
  union _cpp_hashnode_value GTY ((desc ("CPP_HASHNODE_VALUE_IDX (%1)"))) value;
};