gdb/expression.h

   1 /* Definitions for expressions stored in reversed prefix form, for GDB.
   2
   3    Copyright (C) 1986, 1989, 1992, 1994, 2000, 2003, 2005, 2007, 2008
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  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 (the deleted) Chill and Pascal. */
 113     BINOP_IN,                   /* Returns 1 iff ARG1 IN ARG2. */
 114
 115     /* This is the "colon operator" used various places in (the
 116        deleted) Chill. */
 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.  (the deleted) Chill syntax:
 126        OP1(OP2:OP3).  Return elements OP2 through OP3 of OP1.  */
 127     TERNOP_SLICE,
 128
 129     /* A sub-string/sub-array.  (The deleted) Chill syntax: OP1(OP2 UP
 130        OP3).  Return OP3 elements of OP1, starting with element
 131        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 a string in the next exp_element.
 168        This is the name of a register to fetch.  */
 169     OP_REGISTER,
 170
 171     /* OP_INTERNALVAR is followed by an internalvar ptr in the next exp_element.
 172        With another OP_INTERNALVAR at the end, this makes three exp_elements.  */
 173     OP_INTERNALVAR,
 174
 175     /* OP_FUNCALL is followed by an integer in the next exp_element.
 176        The integer is the number of args to the function call.
 177        That many plus one values from following subexpressions
 178        are used, the first one being the function.
 179        The integer is followed by a repeat of OP_FUNCALL,
 180        making three exp_elements.  */
 181     OP_FUNCALL,
 182
 183     /* OP_OBJC_MSGCALL is followed by a string in the next exp_element and then an
 184        integer.  The string is the selector string.  The integer is the number
 185        of arguments to the message call.  That many plus one values are used,
 186        the first one being the object pointer.  This is an Objective C message */
 187     OP_OBJC_MSGCALL,
 188
 189     /* This is EXACTLY like OP_FUNCALL but is semantically different.
 190        In F77, array subscript expressions, substring expressions
 191        and function calls are  all exactly the same syntactically. They may
 192        only be disambiguated at runtime.  Thus this operator, which
 193        indicates that we have found something of the form <name> ( <stuff> ) */
 194     OP_F77_UNDETERMINED_ARGLIST,
 195
 196     /* The following OP is a special one, it introduces a F77 complex
 197        literal. It is followed by exactly two args that are doubles.  */
 198     OP_COMPLEX,
 199
 200     /* OP_STRING represents a string constant.
 201        Its format is the same as that of a STRUCTOP, but the string
 202        data is just made into a string constant when the operation
 203        is executed.  */
 204     OP_STRING,
 205
 206     /* OP_BITSTRING represents a packed bitstring constant.
 207        Its format is the same as that of a STRUCTOP, but the bitstring
 208        data is just made into a bitstring constant when the operation
 209        is executed.  */
 210     OP_BITSTRING,
 211
 212     /* OP_ARRAY creates an array constant out of the following subexpressions.
 213        It is followed by two exp_elements, the first containing an integer
 214        that is the lower bound of the array and the second containing another
 215        integer that is the upper bound of the array.  The second integer is
 216        followed by a repeat of OP_ARRAY, making four exp_elements total.
 217        The bounds are used to compute the number of following subexpressions
 218        to consume, as well as setting the bounds in the created array constant.
 219        The type of the elements is taken from the type of the first subexp,
 220        and they must all match. */
 221     OP_ARRAY,
 222
 223     /* UNOP_CAST is followed by a type pointer in the next exp_element.
 224        With another UNOP_CAST at the end, this makes three exp_elements.
 225        It casts the value of the following subexpression.  */
 226     UNOP_CAST,
 227
 228     /* UNOP_MEMVAL is followed by a type pointer in the next exp_element
 229        With another UNOP_MEMVAL at the end, this makes three exp_elements.
 230        It casts the contents of the word addressed by the value of the
 231        following subexpression.  */
 232     UNOP_MEMVAL,
 233
 234     /* UNOP_MEMVAL_TLS is followed by a `struct objfile' pointer in the next
 235        exp_element and a type pointer in the following exp_element.
 236        With another UNOP_MEMVAL_TLS at the end, this makes four exp_elements.
 237        It casts the contents of the word offsetted by the value of the
 238        following subexpression from the TLS specified by `struct objfile'.  */
 239     UNOP_MEMVAL_TLS,
 240
 241     /* UNOP_... operate on one value from a following subexpression
 242        and replace it with a result.  They take no immediate arguments.  */
 243
 244     UNOP_NEG,                   /* Unary - */
 245     UNOP_LOGICAL_NOT,           /* Unary ! */
 246     UNOP_COMPLEMENT,            /* Unary ~ */
 247     UNOP_IND,                   /* Unary * */
 248     UNOP_ADDR,                  /* Unary & */
 249     UNOP_PREINCREMENT,          /* ++ before an expression */
 250     UNOP_POSTINCREMENT,         /* ++ after an expression */
 251     UNOP_PREDECREMENT,          /* -- before an expression */
 252     UNOP_POSTDECREMENT,         /* -- after an expression */
 253     UNOP_SIZEOF,                /* Unary sizeof (followed by expression) */
 254
 255     UNOP_PLUS,                  /* Unary plus */
 256
 257     UNOP_CAP,                   /* Modula-2 standard (unary) procedures */
 258     UNOP_CHR,
 259     UNOP_ORD,
 260     UNOP_ABS,
 261     UNOP_FLOAT,
 262     UNOP_HIGH,
 263     UNOP_MAX,
 264     UNOP_MIN,
 265     UNOP_ODD,
 266     UNOP_TRUNC,
 267
 268     /* (The deleted) Chill builtin functions.  */
 269     UNOP_LOWER, UNOP_UPPER, UNOP_LENGTH, UNOP_CARD, UNOP_CHMAX, UNOP_CHMIN,
 270
 271     OP_BOOL,                    /* Modula-2 builtin BOOLEAN type */
 272     OP_M2_STRING,               /* Modula-2 string constants */
 273
 274     /* STRUCTOP_... operate on a value from a following subexpression
 275        by extracting a structure component specified by a string
 276        that appears in the following exp_elements (as many as needed).
 277        STRUCTOP_STRUCT is used for "." and STRUCTOP_PTR for "->".
 278        They differ only in the error message given in case the value is
 279        not suitable or the structure component specified is not found.
 280
 281        The length of the string follows the opcode, followed by
 282        BYTES_TO_EXP_ELEM(length) elements containing the data of the
 283        string, followed by the length again and the opcode again.  */
 284
 285     STRUCTOP_STRUCT,
 286     STRUCTOP_PTR,
 287
 288     /* C++: OP_THIS is just a placeholder for the class instance variable.
 289        It just comes in a tight (OP_THIS, OP_THIS) pair.  */
 290     OP_THIS,
 291
 292     /* Objective-C: OP_OBJC_SELF is just a placeholder for the class instance
 293        variable.  It just comes in a tight (OP_OBJC_SELF, OP_OBJC_SELF) pair.  */
 294     OP_OBJC_SELF,
 295
 296     /* Objective C: "@selector" pseudo-operator */
 297     OP_OBJC_SELECTOR,
 298
 299     /* OP_SCOPE surrounds a type name and a field name.  The type
 300        name is encoded as one element, but the field name stays as
 301        a string, which, of course, is variable length.  */
 302     OP_SCOPE,
 303
 304     /* Used to represent named structure field values in brace
 305        initializers (or tuples as they are called in (the deleted)
 306        Chill).
 307
 308        The gcc C syntax is NAME:VALUE or .NAME=VALUE, the (the
 309        deleted) Chill syntax is .NAME:VALUE.  Multiple labels (as in
 310        the (the deleted) Chill syntax .NAME1,.NAME2:VALUE) is
 311        represented as if it were .NAME1:(.NAME2:VALUE) (though that is
 312        not valid (the deleted) Chill syntax).
 313
 314        The NAME is represented as for STRUCTOP_STRUCT;  VALUE follows. */
 315     OP_LABELED,
 316
 317     /* OP_TYPE is for parsing types, and used with the "ptype" command
 318        so we can look up types that are qualified by scope, either with
 319        the GDB "::" operator, or the Modula-2 '.' operator. */
 320     OP_TYPE,
 321
 322     /* An un-looked-up identifier. */
 323     OP_NAME,
 324
 325     /* An Objective C Foundation Class NSString constant */
 326     OP_OBJC_NSSTRING,
 327
 328     /* A F90 array range operator (for "exp:exp", "exp:", ":exp" and ":").  */
 329     OP_F90_RANGE,
 330
 331     /* OP_DECFLOAT is followed by a type pointer in the next exp_element
 332        and a dec long constant value in the following exp_element.
 333        Then comes another OP_DECFLOAT.  */
 334     OP_DECFLOAT,
 335
 336      /* First extension operator.  Individual language modules define
 337         extra operators they need as constants with values
 338         OP_LANGUAGE_SPECIFIC0 + k, for k >= 0, using a separate
 339         enumerated type definition:
 340            enum foo_extension_operator {
 341              BINOP_MOGRIFY = OP_EXTENDED0,
 342              BINOP_FROB,
 343              ...
 344            };      */
 345     OP_EXTENDED0,
 346
 347     /* Last possible extension operator.  Defined to provide an
 348        explicit and finite number of extended operators. */
 349     OP_EXTENDED_LAST = 0xff
 350     /* NOTE: Eventually, we expect to convert to an object-oriented
 351        formulation for expression operators that does away with the
 352        need for these extension operators, and indeed for this
 353        entire enumeration type.  Therefore, consider the OP_EXTENDED
 354        definitions to be a temporary measure. */
 355   };
 356
 357 union exp_element
 358   {
 359     enum exp_opcode opcode;
 360     struct symbol *symbol;
 361     LONGEST longconst;
 362     DOUBLEST doubleconst;
 363     gdb_byte decfloatconst[16];
 364     /* Really sizeof (union exp_element) characters (or less for the last
 365        element of a string).  */
 366     char string;
 367     struct type *type;
 368     struct internalvar *internalvar;
 369     struct block *block;
 370     struct objfile *objfile;
 371   };
 372
 373 struct expression
 374   {
 375     const struct language_defn *language_defn;  /* language it was entered in */
 376     int nelts;
 377     union exp_element elts[1];
 378   };
 379
 380 /* Macros for converting between number of expression elements and bytes
 381    to store that many expression elements. */
 382
 383 #define EXP_ELEM_TO_BYTES(elements) \
 384     ((elements) * sizeof (union exp_element))
 385 #define BYTES_TO_EXP_ELEM(bytes) \
 386     (((bytes) + sizeof (union exp_element) - 1) / sizeof (union exp_element))
 387
 388 /* From parse.c */
 389
 390 extern struct expression *parse_expression (char *);
 391
 392 extern struct type *parse_field_expression (char *, char **);
 393
 394 extern struct expression *parse_exp_1 (char **, struct block *, int);
 395
 396 /* For use by parsers; set if we want to parse an expression and
 397    attempt to complete a field name.  */
 398 extern int in_parse_field;
 399
 400 /* The innermost context required by the stack and register variables
 401    we've encountered so far.  To use this, set it to NULL, then call
 402    parse_<whatever>, then look at it.  */
 403 extern struct block *innermost_block;
 404
 405 /* From eval.c */
 406
 407 /* Values of NOSIDE argument to eval_subexp.  */
 408
 409 enum noside
 410   {
 411     EVAL_NORMAL,
 412     EVAL_SKIP,                  /* Only effect is to increment pos.  */
 413     EVAL_AVOID_SIDE_EFFECTS     /* Don't modify any variables or
 414                                    call any functions.  The value
 415                                    returned will have the correct
 416                                    type, and will have an
 417                                    approximately correct lvalue
 418                                    type (inaccuracy: anything that is
 419                                    listed as being in a register in
 420                                    the function in which it was
 421                                    declared will be lval_register).  */
 422   };
 423
 424 extern struct value *evaluate_subexp_standard
 425   (struct type *, struct expression *, int *, enum noside);
 426
 427 /* From expprint.c */
 428
 429 extern void print_expression (struct expression *, struct ui_file *);
 430
 431 extern char *op_string (enum exp_opcode);
 432
 433 extern void dump_raw_expression (struct expression *, struct ui_file *, char *);
 434 extern void dump_prefix_expression (struct expression *, struct ui_file *);
 435
 436 #endif /* !defined (EXPRESSION_H) */