gdb/expression.h

   1 /* Definitions for expressions stored in reversed prefix form, for GDB.
   2    Copyright 1986, 1989, 1992, 1994, 2000 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program 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 of the License, or
   9    (at your option) any later version.
  10
  11    This program 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 this program; if not, write to the Free Software
  18    Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #if !defined (EXPRESSION_H)
  22 #define EXPRESSION_H 1
  23
  24
  25 #include "symtab.h"             /* Needed for "struct block" type. */
  26 #include "doublest.h"           /* Needed for DOUBLEST.  */
  27
  28
  29 /* Definitions for saved C expressions.  */
  30
  31 /* An expression is represented as a vector of union exp_element's.
  32    Each exp_element is an opcode, except that some opcodes cause
  33    the following exp_element to be treated as a long or double constant
  34    or as a variable.  The opcodes are obeyed, using a stack for temporaries.
  35    The value is left on the temporary stack at the end.  */
  36
  37 /* When it is necessary to include a string,
  38    it can occupy as many exp_elements as it needs.
  39    We find the length of the string using strlen,
  40    divide to find out how many exp_elements are used up,
  41    and skip that many.  Strings, like numbers, are indicated
  42    by the preceding opcode.  */
  43
  44 enum exp_opcode
  45   {
  46     /* Used when it's necessary to pass an opcode which will be ignored,
  47        or to catch uninitialized values.  */
  48     OP_NULL,
  49
  50 /* BINOP_... operate on two values computed by following subexpressions,
  51    replacing them by one result value.  They take no immediate arguments.  */
  52
  53     BINOP_ADD,                  /* + */
  54     BINOP_SUB,                  /* - */
  55     BINOP_MUL,                  /* * */
  56     BINOP_DIV,                  /* / */
  57     BINOP_REM,                  /* % */
  58     BINOP_MOD,                  /* mod (Knuth 1.2.4) */
  59     BINOP_LSH,                  /* << */
  60     BINOP_RSH,                  /* >> */
  61     BINOP_LOGICAL_AND,          /* && */
  62     BINOP_LOGICAL_OR,           /* || */
  63     BINOP_BITWISE_AND,          /* & */
  64     BINOP_BITWISE_IOR,          /* | */
  65     BINOP_BITWISE_XOR,          /* ^ */
  66     BINOP_EQUAL,                /* == */
  67     BINOP_NOTEQUAL,             /* != */
  68     BINOP_LESS,                 /* < */
  69     BINOP_GTR,                  /* > */
  70     BINOP_LEQ,                  /* <= */
  71     BINOP_GEQ,                  /* >= */
  72     BINOP_REPEAT,               /* @ */
  73     BINOP_ASSIGN,               /* = */
  74     BINOP_COMMA,                /* , */
  75     BINOP_SUBSCRIPT,            /* x[y] */
  76     BINOP_EXP,                  /* Exponentiation */
  77
  78     /* C++.  */
  79
  80     BINOP_MIN,                  /* <? */
  81     BINOP_MAX,                  /* >? */
  82
  83     /* STRUCTOP_MEMBER is used for pointer-to-member constructs.
  84        X . * Y translates into X STRUCTOP_MEMBER Y.  */
  85     STRUCTOP_MEMBER,
  86
  87     /* STRUCTOP_MPTR is used for pointer-to-member constructs
  88        when X is a pointer instead of an aggregate.  */
  89     STRUCTOP_MPTR,
  90
  91     /* end of C++.  */
  92
  93     /* For Modula-2 integer division DIV */
  94     BINOP_INTDIV,
  95
  96     BINOP_ASSIGN_MODIFY,        /* +=, -=, *=, and so on.
  97                                    The following exp_element is another opcode,
  98                                    a BINOP_, saying how to modify.
  99                                    Then comes another BINOP_ASSIGN_MODIFY,
 100                                    making three exp_elements in total.  */
 101
 102     /* Modula-2 standard (binary) procedures */
 103     BINOP_VAL,
 104     BINOP_INCL,
 105     BINOP_EXCL,
 106
 107     /* Concatenate two operands, such as character strings or bitstrings.
 108        If the first operand is a integer expression, then it means concatenate
 109        the second operand with itself that many times. */
 110     BINOP_CONCAT,
 111
 112     /* For (OBSOLETE) Chill (OBSOLETE) and Pascal. */
 113     BINOP_IN,                   /* Returns 1 iff ARG1 IN ARG2. */
 114
 115     /* This is the "colon operator" used various places in (OBSOLETE)
 116        Chill (OBSOLETE). */
 117     BINOP_RANGE,
 118
 119     /* This must be the highest BINOP_ value, for expprint.c.  */
 120     BINOP_END,
 121
 122     /* Operates on three values computed by following subexpressions.  */
 123     TERNOP_COND,                /* ?: */
 124
 125     /* A sub-string/sub-array.  (OBSOLETE) Chill (OBSOLETE) syntax:
 126        OP1(OP2:OP3).  Return elements OP2 through OP3 of OP1.  */
 127     TERNOP_SLICE,
 128
 129     /* A sub-string/sub-array.  (OBSOLETE) Chill (OBSOLETE) syntax:
 130        OP1(OP2 UP OP3).  Return OP3 elements of OP1, starting with
 131        element OP2. */
 132     TERNOP_SLICE_COUNT,
 133
 134     /* Multidimensional subscript operator, such as Modula-2 x[a,b,...].
 135        The dimensionality is encoded in the operator, like the number of
 136        function arguments in OP_FUNCALL, I.E. <OP><dimension><OP>.
 137        The value of the first following subexpression is subscripted
 138        by each of the next following subexpressions, one per dimension. */
 139     MULTI_SUBSCRIPT,
 140
 141     /* The OP_... series take immediate following arguments.
 142        After the arguments come another OP_... (the same one)
 143        so that the grouping can be recognized from the end.  */
 144
 145     /* OP_LONG is followed by a type pointer in the next exp_element
 146        and the long constant value in the following exp_element.
 147        Then comes another OP_LONG.
 148        Thus, the operation occupies four exp_elements.  */
 149     OP_LONG,
 150
 151     /* OP_DOUBLE is similar but takes a DOUBLEST constant instead of a long.  */
 152     OP_DOUBLE,
 153
 154     /* OP_VAR_VALUE takes one struct block * in the following element,
 155        and one struct symbol * in the following exp_element, followed by
 156        another OP_VAR_VALUE, making four exp_elements.  If the block is
 157        non-NULL, evaluate the symbol relative to the innermost frame
 158        executing in that block; if the block is NULL use the selected frame.  */
 159     OP_VAR_VALUE,
 160
 161     /* OP_LAST is followed by an integer in the next exp_element.
 162        The integer is zero for the last value printed,
 163        or it is the absolute number of a history element.
 164        With another OP_LAST at the end, this makes three exp_elements.  */
 165     OP_LAST,
 166
 167     /* OP_REGISTER is followed by an integer in the next exp_element.
 168        This is the number of a register to fetch (as an int).
 169        With another OP_REGISTER at the end, this makes three exp_elements.  */
 170     OP_REGISTER,
 171
 172     /* OP_INTERNALVAR is followed by an internalvar ptr in the next exp_element.
 173        With another OP_INTERNALVAR at the end, this makes three exp_elements.  */
 174     OP_INTERNALVAR,
 175
 176     /* OP_FUNCALL is followed by an integer in the next exp_element.
 177        The integer is the number of args to the function call.
 178        That many plus one values from following subexpressions
 179        are used, the first one being the function.
 180        The integer is followed by a repeat of OP_FUNCALL,
 181        making three exp_elements.  */
 182     OP_FUNCALL,
 183
 184     /* This is EXACTLY like OP_FUNCALL but is semantically different.
 185        In F77, array subscript expressions, substring expressions
 186        and function calls are  all exactly the same syntactically. They may
 187        only be dismabiguated at runtime.  Thus this operator, which
 188        indicates that we have found something of the form <name> ( <stuff> ) */
 189     OP_F77_UNDETERMINED_ARGLIST,
 190
 191     /* The following OP is a special one, it introduces a F77 complex
 192        literal. It is followed by exactly two args that are doubles.  */
 193     OP_COMPLEX,
 194
 195     /* OP_STRING represents a string constant.
 196        Its format is the same as that of a STRUCTOP, but the string
 197        data is just made into a string constant when the operation
 198        is executed.  */
 199     OP_STRING,
 200
 201     /* OP_BITSTRING represents a packed bitstring constant.
 202        Its format is the same as that of a STRUCTOP, but the bitstring
 203        data is just made into a bitstring constant when the operation
 204        is executed.  */
 205     OP_BITSTRING,
 206
 207     /* OP_ARRAY creates an array constant out of the following subexpressions.
 208        It is followed by two exp_elements, the first containing an integer
 209        that is the lower bound of the array and the second containing another
 210        integer that is the upper bound of the array.  The second integer is
 211        followed by a repeat of OP_ARRAY, making four exp_elements total.
 212        The bounds are used to compute the number of following subexpressions
 213        to consume, as well as setting the bounds in the created array constant.
 214        The type of the elements is taken from the type of the first subexp,
 215        and they must all match. */
 216     OP_ARRAY,
 217
 218     /* UNOP_CAST is followed by a type pointer in the next exp_element.
 219        With another UNOP_CAST at the end, this makes three exp_elements.
 220        It casts the value of the following subexpression.  */
 221     UNOP_CAST,
 222
 223     /* UNOP_MEMVAL is followed by a type pointer in the next exp_element
 224        With another UNOP_MEMVAL at the end, this makes three exp_elements.
 225        It casts the contents of the word addressed by the value of the
 226        following subexpression.  */
 227     UNOP_MEMVAL,
 228
 229     /* UNOP_... operate on one value from a following subexpression
 230        and replace it with a result.  They take no immediate arguments.  */
 231
 232     UNOP_NEG,                   /* Unary - */
 233     UNOP_LOGICAL_NOT,           /* Unary ! */
 234     UNOP_COMPLEMENT,            /* Unary ~ */
 235     UNOP_IND,                   /* Unary * */
 236     UNOP_ADDR,                  /* Unary & */
 237     UNOP_PREINCREMENT,          /* ++ before an expression */
 238     UNOP_POSTINCREMENT,         /* ++ after an expression */
 239     UNOP_PREDECREMENT,          /* -- before an expression */
 240     UNOP_POSTDECREMENT,         /* -- after an expression */
 241     UNOP_SIZEOF,                /* Unary sizeof (followed by expression) */
 242
 243     UNOP_PLUS,                  /* Unary plus */
 244
 245     UNOP_CAP,                   /* Modula-2 standard (unary) procedures */
 246     UNOP_CHR,
 247     UNOP_ORD,
 248     UNOP_ABS,
 249     UNOP_FLOAT,
 250     UNOP_HIGH,
 251     UNOP_MAX,
 252     UNOP_MIN,
 253     UNOP_ODD,
 254     UNOP_TRUNC,
 255
 256     /* (OBSOLETE) Chill (OBSOLETE) builtin functions. */
 257     UNOP_LOWER, UNOP_UPPER, UNOP_LENGTH, UNOP_CARD, UNOP_CHMAX, UNOP_CHMIN,
 258
 259     OP_BOOL,                    /* Modula-2 builtin BOOLEAN type */
 260     OP_M2_STRING,               /* Modula-2 string constants */
 261
 262     /* STRUCTOP_... operate on a value from a following subexpression
 263        by extracting a structure component specified by a string
 264        that appears in the following exp_elements (as many as needed).
 265        STRUCTOP_STRUCT is used for "." and STRUCTOP_PTR for "->".
 266        They differ only in the error message given in case the value is
 267        not suitable or the structure component specified is not found.
 268
 269        The length of the string follows the opcode, followed by
 270        BYTES_TO_EXP_ELEM(length) elements containing the data of the
 271        string, followed by the length again and the opcode again.  */
 272
 273     STRUCTOP_STRUCT,
 274     STRUCTOP_PTR,
 275
 276     /* C++ */
 277     /* OP_THIS is just a placeholder for the class instance variable.
 278        It just comes in a tight (OP_THIS, OP_THIS) pair.  */
 279     OP_THIS,
 280
 281     /* OP_SCOPE surrounds a type name and a field name.  The type
 282        name is encoded as one element, but the field name stays as
 283        a string, which, of course, is variable length.  */
 284     OP_SCOPE,
 285
 286     /* Used to represent named structure field values in brace
 287        initializers (or tuples as they are called in (OBSOLETE) Chill
 288        (OBSOLETE)).
 289
 290        The gcc C syntax is NAME:VALUE or .NAME=VALUE, the (OBSOLETE)
 291        Chill (OBSOLETE) syntax is .NAME:VALUE.  Multiple labels (as in
 292        the (OBSOLETE) Chill (OBSOLETE) syntax .NAME1,.NAME2:VALUE) is
 293        represented as if it were .NAME1:(.NAME2:VALUE) (though that is
 294        not valid (OBSOLETE) Chill (OBSOLETE) syntax).
 295
 296        The NAME is represented as for STRUCTOP_STRUCT;  VALUE follows. */
 297     OP_LABELED,
 298
 299     /* OP_TYPE is for parsing types, and used with the "ptype" command
 300        so we can look up types that are qualified by scope, either with
 301        the GDB "::" operator, or the Modula-2 '.' operator. */
 302     OP_TYPE,
 303
 304     /* An un-looked-up identifier. */
 305     OP_NAME,
 306
 307     /* An unparsed expression.  Used for Scheme (for now at least) */
 308     OP_EXPRSTRING
 309   };
 310
 311 union exp_element
 312   {
 313     enum exp_opcode opcode;
 314     struct symbol *symbol;
 315     LONGEST longconst;
 316     DOUBLEST doubleconst;
 317     /* Really sizeof (union exp_element) characters (or less for the last
 318        element of a string).  */
 319     char string;
 320     struct type *type;
 321     struct internalvar *internalvar;
 322     struct block *block;
 323   };
 324
 325 struct expression
 326   {
 327     const struct language_defn *language_defn;  /* language it was entered in */
 328     int nelts;
 329     union exp_element elts[1];
 330   };
 331
 332 /* Macros for converting between number of expression elements and bytes
 333    to store that many expression elements. */
 334
 335 #define EXP_ELEM_TO_BYTES(elements) \
 336     ((elements) * sizeof (union exp_element))
 337 #define BYTES_TO_EXP_ELEM(bytes) \
 338     (((bytes) + sizeof (union exp_element) - 1) / sizeof (union exp_element))
 339
 340 /* From parse.c */
 341
 342 extern struct expression *parse_expression (char *);
 343
 344 extern struct expression *parse_exp_1 (char **, struct block *, int);
 345
 346 /* The innermost context required by the stack and register variables
 347    we've encountered so far.  To use this, set it to NULL, then call
 348    parse_<whatever>, then look at it.  */
 349 extern struct block *innermost_block;
 350
 351 /* From eval.c */
 352
 353 /* Values of NOSIDE argument to eval_subexp.  */
 354
 355 enum noside
 356   {
 357     EVAL_NORMAL,
 358     EVAL_SKIP,                  /* Only effect is to increment pos.  */
 359     EVAL_AVOID_SIDE_EFFECTS     /* Don't modify any variables or
 360                                    call any functions.  The value
 361                                    returned will have the correct
 362                                    type, and will have an
 363                                    approximately correct lvalue
 364                                    type (inaccuracy: anything that is
 365                                    listed as being in a register in
 366                                    the function in which it was
 367                                    declared will be lval_register).  */
 368   };
 369
 370 extern struct value *evaluate_subexp_standard
 371   (struct type *, struct expression *, int *, enum noside);
 372
 373 /* From expprint.c */
 374
 375 extern void print_expression (struct expression *, struct ui_file *);
 376
 377 extern char *op_string (enum exp_opcode);
 378
 379 extern void dump_prefix_expression (struct expression *,
 380                                     struct ui_file *,
 381                                     char *);
 382 extern void dump_postfix_expression (struct expression *,
 383                                      struct ui_file *,
 384                                      char *);
 385
 386 #endif /* !defined (EXPRESSION_H) */