class.h

gcc库的原代码,对编程有很大帮助.

/* Variables and structures for overloading rules.
   Copyright (C) 1993 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* The following structure is used when comparing various alternatives
   for overloading.  The unsigned quantity `strikes.i' is used
   for fast comparison of two possibilities.  This number is an
   aggregate of four constituents:

     EVIL: if this is non-zero, then the candidate should not be considered
     ELLIPSIS: if this is non-zero, then some actual argument has been matched
               against an ellipsis
     USER: if this is non-zero, then a user-defined type conversion is needed
     B_OR_D: if this is non-zero, then use a base pointer instead of the
             type of the pointer we started with.
     EASY: if this is non-zero, then we have a builtin conversion
           (such as int to long, int to float, etc) to do.

   If two candidates require user-defined type conversions, and the
   type conversions are not identical, then an ambiguity error
   is reported.

   If two candidates agree on user-defined type conversions,
   and one uses pointers of strictly higher type (derived where
   another uses base), then that alternative is silently chosen.

   Note that this technique really only works for 255 arguments.  Perhaps
   this is not enough.  */

/* These macros and harshness_code are used by the NEW METHOD.  */
#define EVIL_CODE (1<<7)
#define CONST_CODE (1<<6)
#define ELLIPSIS_CODE (1<<5)
#define USER_CODE (1<<4)
#define STD_CODE (1<<3)
#define PROMO_CODE (1<<2)
#define QUAL_CODE (1<<1)
#define TRIVIAL_CODE (1<<0)

struct harshness_code
{
  /* What kind of conversion is involved.  */
  unsigned short code;

  /* The inheritance distance.  */
  short distance;

  /* For a PROMO_CODE, Any special penalties involved in integral conversions.
     This exists because $4.1 of the ARM states that something like
     `short unsigned int' should promote to `int', not `unsigned int'.
     If, for example, it tries to match two fns, f(int) and f(unsigned),
     f(int) should be a better match than f(unsigned) by this rule.  Without
     this extra metric, they both only appear as "integral promotions", which
     will lead to an ambiguity.
     For a TRIVIAL_CODE, This is also used by build_overload_call_real and
     convert_harshness to keep track of other information we need.  */
  unsigned short int_penalty;
};

struct candidate
{
  struct harshness_code h;	/* Used for single-argument conversions.  */

  int h_len;			/* The length of the harshness vector.  */

  tree function;		/* A FUNCTION_DECL */
  tree basetypes;		/* The path to function. */
  tree arg;			/* first parm to function.  */

  /* Indexed by argument number, encodes evil, user, d_to_b, and easy
     strikes for that argument.  At end of array, we store the index+1
     of where we started using default parameters, or 0 if there are
     none.  */
  struct harshness_code *harshness;

  union
    {
      tree field;		/* If no evil strikes, the FUNCTION_DECL of
				   the function (if a member function).  */
      int bad_arg;		/* the index of the first bad argument:
				   0 if no bad arguments
				   > 0 is first bad argument
				   -1 if extra actual arguments
				   -2 if too few actual arguments.
				   -3 if const/non const method mismatch.
				   -4 if type unification failed.
				   -5 if contravariance violation.  */
    } u;
};
int rank_for_overload ();

/* Variables shared between class.c and call.c.  */

extern int n_vtables;
extern int n_vtable_entries;
extern int n_vtable_searches;
extern int n_vtable_elems;
extern int n_convert_harshness;
extern int n_compute_conversion_costs;
extern int n_build_method_call;
extern int n_inner_fields_searched;