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1.1 root 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;
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