gcc/cp/class.h

   1 /* Variables and structures for overloading rules.
   2    Copyright (C) 1993 Free Software Foundation, Inc.
   3
   4 This file is part of GNU CC.
   5
   6 GNU CC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU CC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU CC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 /* The following structure is used when comparing various alternatives
  21    for overloading.  The unsigned quantity `strikes.i' is used
  22    for fast comparison of two possibilities.  This number is an
  23    aggregate of four constituents:
  24
  25      EVIL: if this is non-zero, then the candidate should not be considered
  26      ELLIPSIS: if this is non-zero, then some actual argument has been matched
  27                against an ellipsis
  28      USER: if this is non-zero, then a user-defined type conversion is needed
  29      B_OR_D: if this is non-zero, then use a base pointer instead of the
  30              type of the pointer we started with.
  31      EASY: if this is non-zero, then we have a builtin conversion
  32            (such as int to long, int to float, etc) to do.
  33
  34    If two candidates require user-defined type conversions, and the
  35    type conversions are not identical, then an ambiguity error
  36    is reported.
  37
  38    If two candidates agree on user-defined type conversions,
  39    and one uses pointers of strictly higher type (derived where
  40    another uses base), then that alternative is silently chosen.
  41
  42    Note that this technique really only works for 255 arguments.  Perhaps
  43    this is not enough.  */
  44
  45 /* These macros and harshness_code are used by the NEW METHOD.  */
  46 #define EVIL_CODE (1<<7)
  47 #define CONST_CODE (1<<6)
  48 #define ELLIPSIS_CODE (1<<5)
  49 #define USER_CODE (1<<4)
  50 #define STD_CODE (1<<3)
  51 #define PROMO_CODE (1<<2)
  52 #define QUAL_CODE (1<<1)
  53 #define TRIVIAL_CODE (1<<0)
  54
  55 struct harshness_code
  56 {
  57   /* What kind of conversion is involved.  */
  58   unsigned short code;
  59
  60   /* The inheritance distance.  */
  61   short distance;
  62
  63   /* For a PROMO_CODE, Any special penalties involved in integral conversions.
  64      This exists because $4.1 of the ARM states that something like
  65      `short unsigned int' should promote to `int', not `unsigned int'.
  66      If, for example, it tries to match two fns, f(int) and f(unsigned),
  67      f(int) should be a better match than f(unsigned) by this rule.  Without
  68      this extra metric, they both only appear as "integral promotions", which
  69      will lead to an ambiguity.
  70      For a TRIVIAL_CODE, This is also used by build_overload_call_real and
  71      convert_harshness to keep track of other information we need.  */
  72   unsigned short int_penalty;
  73 };
  74
  75 struct candidate
  76 {
  77   struct harshness_code h;      /* Used for single-argument conversions.  */
  78
  79   int h_len;                    /* The length of the harshness vector.  */
  80
  81   tree function;                /* A FUNCTION_DECL */
  82   tree basetypes;               /* The path to function. */
  83   tree arg;                     /* first parm to function.  */
  84
  85   /* Indexed by argument number, encodes evil, user, d_to_b, and easy
  86      strikes for that argument.  At end of array, we store the index+1
  87      of where we started using default parameters, or 0 if there are
  88      none.  */
  89   struct harshness_code *harshness;
  90
  91   union
  92     {
  93       tree field;               /* If no evil strikes, the FUNCTION_DECL of
  94                                    the function (if a member function).  */
  95       int bad_arg;              /* the index of the first bad argument:
  96                                    0 if no bad arguments
  97                                    > 0 is first bad argument
  98                                    -1 if extra actual arguments
  99                                    -2 if too few actual arguments.
 100                                    -3 if const/non const method mismatch.
 101                                    -4 if type unification failed.
 102                                    -5 if contravariance violation.  */
 103     } u;
 104 };
 105 int rank_for_overload ();
 106
 107 /* Variables shared between class.c and call.c.  */
 108
 109 extern int n_vtables;
 110 extern int n_vtable_entries;
 111 extern int n_vtable_searches;
 112 extern int n_vtable_elems;
 113 extern int n_convert_harshness;
 114 extern int n_compute_conversion_costs;
 115 extern int n_build_method_call;
 116 extern int n_inner_fields_searched;