projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 9bf86ebb PR |
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 | If two candidates have a non-monotonic derived/base pointer | |
| 43 | relationship, and/or a non-monotonic easy conversion relationship, | |
| 44 | then a warning is emitted to show which paths are possible, and | |
| 45 | which one is being chosen. | |
| 46 | ||
| 47 | For example: | |
| 48 | ||
| 49 | int i; | |
| 50 | double x; | |
| 51 | ||
| 52 | overload f; | |
| 53 | int f (int, int); | |
| 54 | double f (double, double); | |
| 55 | ||
| 56 | f (i, x); // draws a warning | |
| 57 | ||
| 58 | struct B | |
| 59 | { | |
| 60 | f (int); | |
| 61 | } *bb; | |
| 62 | struct D : B | |
| 63 | { | |
| 64 | f (double); | |
| 65 | } *dd; | |
| 66 | ||
| 67 | dd->f (x); // exact match | |
| 68 | dd->f (i); // draws warning | |
| 69 | ||
| 70 | Note that this technique really only works for 255 arguments. Perhaps | |
| 71 | this is not enough. */ | |
| 72 | ||
| 73 | struct candidate | |
| 74 | { | |
| 75 | tree function; /* A FUNCTION_DECL */ | |
| 76 | ||
| 77 | unsigned char evil; /* !0 if this will never convert. */ | |
| 78 | unsigned char ellipsis; /* !0 if a match against an ellipsis occurred */ | |
| 79 | unsigned char user; /* !0 if at least one user-defined type conv. */ | |
| 80 | unsigned short b_or_d; /* count number of derived->base or | |
| 81 | base->derived conv. */ | |
| 82 | unsigned short easy; /* count number of builtin type conv. */ | |
| 83 | tree arg; /* first parm to function. */ | |
| 84 | unsigned short *harshness; /* Indexed by argument number, encodes | |
| 85 | evil, user, d_to_b, and easy strikes for | |
| 86 | that argument. | |
| 87 | At end of array, we store the index+1 | |
| 88 | of where we started using default | |
| 89 | parameters, or 0 if there are none. */ | |
| 90 | union | |
| 91 | { | |
| 92 | tree field; /* If no evil strikes, the FUNCTION_DECL of | |
| 93 | the function (if a member function). */ | |
| 94 | int bad_arg; /* the index of the first bad argument: | |
| 95 | 0 if no bad arguments | |
| 96 | > 0 is first bad argument | |
| 97 | -1 if extra actual arguments | |
| 98 | -2 if too few actual arguments. | |
| 99 | -3 if const/non const method mismatch. | |
| 100 | -4 if type unification failed. | |
| 101 | -5 if contravariance violation. */ | |
| 102 | } u; | |
| 103 | }; | |
| 104 | int rank_for_overload (); | |
| 105 | ||
| 106 | /* Variables shared between cp-class.c and cp-call.c. */ | |
| 107 | ||
| 108 | extern int n_vtables; | |
| 109 | extern int n_vtable_entries; | |
| 110 | extern int n_vtable_searches; | |
| 111 | extern int n_vtable_elems; | |
| 112 | extern int n_convert_harshness; | |
| 113 | extern int n_compute_conversion_costs; | |
| 114 | extern int n_build_method_call; | |
| 115 | extern int n_inner_fields_searched; |