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Annotation of GNUtools/cc/cp-class.h, revision 1.1

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:    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: /* These macros and harshness_code are used by the NEW METHOD.  */
        !            74: #define EVIL_CODE (1<<7)
        !            75: #define CONST_CODE (1<<6)
        !            76: #define ELLIPSIS_CODE (1<<5)
        !            77: #define USER_CODE (1<<4)
        !            78: #define STD_CODE (1<<3)
        !            79: #define PROMO_CODE (1<<2)
        !            80: #define QUAL_CODE (1<<1)
        !            81: #define TRIVIAL_CODE (1<<0)
        !            82: 
        !            83: struct harshness_code
        !            84: {
        !            85:   /* What kind of conversion is involved.  */
        !            86:   unsigned short code;
        !            87: 
        !            88:   /* The inheritance distance.  */
        !            89:   short distance;
        !            90: 
        !            91:   /* For a PROMO_CODE, Any special penalties involved in integral conversions.
        !            92:      This exists because $4.1 of the ARM states that something like
        !            93:      `short unsigned int' should promote to `int', not `unsigned int'.
        !            94:      If, for example, it tries to match two fns, f(int) and f(unsigned),
        !            95:      f(int) should be a better match than f(unsigned) by this rule.  Without
        !            96:      this extra metric, they both only appear as "integral promotions", which
        !            97:      will lead to an ambiguity.
        !            98:      For a TRIVIAL_CODE, This is also used by build_overload_call_real and
        !            99:      convert_harshness to keep track of other information we need.  */
        !           100:   unsigned short int_penalty;
        !           101: };
        !           102: 
        !           103: struct candidate
        !           104: {
        !           105:   /* OLD METHOD */
        !           106:   unsigned char evil;        /* !0 if this will never convert.  */
        !           107:   unsigned char ellipsis;     /* !0 if a match against an ellipsis occurred */
        !           108:   unsigned char user;        /* !0 if at least one user-defined type conv.  */
        !           109:   unsigned short b_or_d;      /* count number of derived->base or
        !           110:                                 base->derived conv.  */
        !           111:   unsigned short easy;       /* count number of builtin type conv.  */
        !           112: 
        !           113:   /* NEW METHOD */
        !           114:   struct harshness_code h;     /* Used for single-argument conversions.  */
        !           115: 
        !           116:   int h_len;                   /* The length of the harshness vector.  */
        !           117: 
        !           118:   /* Both methods.  */
        !           119:   tree function;               /* A FUNCTION_DECL */
        !           120:   tree arg;                    /* first parm to function.  */
        !           121: 
        !           122:   /* This union is only here while we maintain both the old and new
        !           123:      argument matching schemes.  When it goes away, all v.ansi_harshness
        !           124:      references will be just `harshness'.  */
        !           125:   union
        !           126:     {
        !           127:       /* Indexed by argument number, encodes evil, user, d_to_b, and easy
        !           128:         strikes for that argument.  At end of array, we store the index+1
        !           129:         of where we started using default parameters, or 0 if there are
        !           130:         none.  */
        !           131:       struct harshness_code *ansi_harshness; /* NEW METHOD */
        !           132:       unsigned short *old_harshness;  /* OLD METHOD */
        !           133:     } v;
        !           134: 
        !           135:   union
        !           136:     {
        !           137:       tree field;              /* If no evil strikes, the FUNCTION_DECL of
        !           138:                                   the function (if a member function).  */
        !           139:       int bad_arg;             /* the index of the first bad argument:
        !           140:                                   0 if no bad arguments
        !           141:                                   > 0 is first bad argument
        !           142:                                   -1 if extra actual arguments
        !           143:                                   -2 if too few actual arguments.
        !           144:                                   -3 if const/non const method mismatch.
        !           145:                                   -4 if type unification failed.
        !           146:                                   -5 if contravariance violation.  */
        !           147:     } u;
        !           148: };
        !           149: int rank_for_overload ();
        !           150: 
        !           151: /* Variables shared between cp-class.c and cp-call.c.  */
        !           152: 
        !           153: extern int n_vtables;
        !           154: extern int n_vtable_entries;
        !           155: extern int n_vtable_searches;
        !           156: extern int n_vtable_elems;
        !           157: extern int n_convert_harshness;
        !           158: extern int n_compute_conversion_costs;
        !           159: extern int n_build_method_call;
        !           160: extern int n_inner_fields_searched;

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