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 Free Software
   4    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 2 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, write to the Free Software
  20    Foundation, Inc., 51 Franklin Street, Fifth Floor,
  21    Boston, MA 02110-1301, USA.  */
  22
  23 #if !defined (EXPRESSION_H)
  24 #define EXPRESSION_H 1
  25
  26
  27 #include "symtab.h"             /* Needed for "struct block" type. */
  28 #include "doublest.h"           /* Needed for DOUBLEST.  */
  29
  30
  31 /* Definitions for saved C expressions.  */
  32
  33 /* An expression is represented as a vector of union exp_element's.
  34    Each exp_element is an opcode, except that some opcodes cause
  35    the following exp_element to be treated as a long or double constant
  36    or as a variable.  The opcodes are obeyed, using a stack for temporaries.
  37    The value is left on the temporary stack at the end.  */
  38
  39 /* When it is necessary to include a string,
  40    it can occupy as many exp_elements as it needs.
  41    We find the length of the string using strlen,
  42    divide to find out how many exp_elements are used up,
  43    and skip that many.  Strings, like numbers, are indicated
  44    by the preceding opcode.  */
  45
  46 enum exp_opcode
  47   {
  48     /* Used when it's necessary to pass an opcode which will be ignored,
  49        or to catch uninitialized values.  */
  50     OP_NULL,
  51
  52 /* BINOP_... operate on two values computed by following subexpressions,
  53    replacing them by one result value.  They take no immediate arguments.  */
  54
  55     BINOP_ADD,                  /* + */
  56     BINOP_SUB,                  /* - */
  57     BINOP_MUL,                  /* * */
  58     BINOP_DIV,                  /* / */
  59     BINOP_REM,                  /* % */
  60     BINOP_MOD,                  /* mod (Knuth 1.2.4) */
  61     BINOP_LSH,                  /* << */
  62     BINOP_RSH,                  /* >> */
  63     BINOP_LOGICAL_AND,          /* && */
  64     BINOP_LOGICAL_OR,           /* || */
  65     BINOP_BITWISE_AND,          /* & */
  66     BINOP_BITWISE_IOR,          /* | */
  67     BINOP_BITWISE_XOR,          /* ^ */
  68     BINOP_EQUAL,                /* == */
  69     BINOP_NOTEQUAL,             /* != */
  70     BINOP_LESS,                 /* < */
  71     BINOP_GTR,                  /* > */
  72     BINOP_LEQ,                  /* <= */
  73     BINOP_GEQ,                  /* >= */
  74     BINOP_REPEAT,               /* @ */
  75     BINOP_ASSIGN,               /* = */
  76     BINOP_COMMA,                /* , */
  77     BINOP_SUBSCRIPT,            /* x[y] */
  78     BINOP_EXP,                  /* Exponentiation */
  79
  80     /* C++.  */
  81
  82     BINOP_MIN,                  /* <? */
  83     BINOP_MAX,                  /* >? */
  84
  85     /* STRUCTOP_MEMBER is used for pointer-to-member constructs.
  86        X . * Y translates into X STRUCTOP_MEMBER Y.  */
  87     STRUCTOP_MEMBER,
  88
  89     /* STRUCTOP_MPTR is used for pointer-to-member constructs
  90        when X is a pointer instead of an aggregate.  */
  91     STRUCTOP_MPTR,
  92
  93     /* end of C++.  */
  94
  95     /* For Modula-2 integer division DIV */
  96     BINOP_INTDIV,
  97
  98     BINOP_ASSIGN_MODIFY,        /* +=, -=, *=, and so on.
  99                                    The following exp_element is another opcode,
 100                                    a BINOP_, saying how to modify.
 101                                    Then comes another BINOP_ASSIGN_MODIFY,
 102                                    making three exp_elements in total.  */
 103
 104     /* Modula-2 standard (binary) procedures */
 105     BINOP_VAL,
 106     BINOP_INCL,
 107     BINOP_EXCL,
 108
 109     /* Concatenate two operands, such as character strings or bitstrings.
 110        If the first operand is a integer expression, then it means concatenate
 111        the second operand with itself that many times. */
 112     BINOP_CONCAT,
 113
 114     /* For (the deleted) Chill and Pascal. */
 115     BINOP_IN,                   /* Returns 1 iff ARG1 IN ARG2. */
 116
 117     /* This is the "colon operator" used various places in (the
 118        deleted) Chill. */
 119     BINOP_RANGE,
 120
 121     /* This must be the highest BINOP_ value, for expprint.c.  */
 122     BINOP_END,
 123
 124     /* Operates on three values computed by following subexpressions.  */
 125     TERNOP_COND,                /* ?: */
 126
 127     /* A sub-string/sub-array.  (the deleted) Chill syntax:
 128        OP1(OP2:OP3).  Return elements OP2 through OP3 of OP1.  */
 129     TERNOP_SLICE,
 130
 131     /* A sub-string/sub-array.  (The deleted) Chill syntax: OP1(OP2 UP
 132        OP3).  Return OP3 elements of OP1, starting with element
 133        OP2. */
 134     TERNOP_SLICE_COUNT,
 135
 136     /* Multidimensional subscript operator, such as Modula-2 x[a,b,...].
 137        The dimensionality is encoded in the operator, like the number of
 138        function arguments in OP_FUNCALL, I.E. <OP><dimension><OP>.
 139        The value of the first following subexpression is subscripted
 140        by each of the next following subexpressions, one per dimension. */
 141     MULTI_SUBSCRIPT,
 142
 143     /* The OP_... series take immediate following arguments.
 144        After the arguments come another OP_... (the same one)
 145        so that the grouping can be recognized from the end.  */
 146
 147     /* OP_LONG is followed by a type pointer in the next exp_element
 148        and the long constant value in the following exp_element.
 149        Then comes another OP_LONG.
 150        Thus, the operation occupies four exp_elements.  */
 151     OP_LONG,
 152
 153     /* OP_DOUBLE is similar but takes a DOUBLEST constant instead of a long.  */
 154     OP_DOUBLE,
 155
 156     /* OP_VAR_VALUE takes one struct block * in the following element,
 157        and one struct symbol * in the following exp_element, followed by
 158        another OP_VAR_VALUE, making four exp_elements.  If the block is
 159        non-NULL, evaluate the symbol relative to the innermost frame
 160        executing in that block; if the block is NULL use the selected frame.  */
 161     OP_VAR_VALUE,
 162
 163     /* OP_LAST is followed by an integer in the next exp_element.
 164        The integer is zero for the last value printed,
 165        or it is the absolute number of a history element.
 166        With another OP_LAST at the end, this makes three exp_elements.  */
 167     OP_LAST,
 168
 169     /* OP_REGISTER is followed by an integer in the next exp_element.
 170        This is the number of a register to fetch (as an int).
 171        With another OP_REGISTER at the end, this makes three exp_elements.  */
 172     OP_REGISTER,
 173
 174     /* OP_INTERNALVAR is followed by an internalvar ptr in the next exp_element.
 175        With another OP_INTERNALVAR at the end, this makes three exp_elements.  */
 176     OP_INTERNALVAR,
 177
 178     /* OP_FUNCALL is followed by an integer in the next exp_element.
 179        The integer is the number of args to the function call.
 180        That many plus one values from following subexpressions
 181        are used, the first one being the function.
 182        The integer is followed by a repeat of OP_FUNCALL,
 183        making three exp_elements.  */
 184     OP_FUNCALL,
 185
 186     /* OP_OBJC_MSGCALL is followed by a string in the next exp_element and then an
 187        integer.  The string is the selector string.  The integer is the number
 188        of arguments to the message call.  That many plus one values are used,
 189        the first one being the object pointer.  This is an Objective C message */
 190     OP_OBJC_MSGCALL,
 191
 192     /* This is EXACTLY like OP_FUNCALL but is semantically different.
 193        In F77, array subscript expressions, substring expressions
 194        and function calls are  all exactly the same syntactically. They may
 195        only be disambiguated at runtime.  Thus this operator, which
 196        indicates that we have found something of the form <name> ( <stuff> ) */
 197     OP_F77_UNDETERMINED_ARGLIST,
 198
 199     /* The following OP is a special one, it introduces a F77 complex
 200        literal. It is followed by exactly two args that are doubles.  */
 201     OP_COMPLEX,
 202
 203     /* OP_STRING represents a string constant.
 204        Its format is the same as that of a STRUCTOP, but the string
 205        data is just made into a string constant when the operation
 206        is executed.  */
 207     OP_STRING,
 208
 209     /* OP_BITSTRING represents a packed bitstring constant.
 210        Its format is the same as that of a STRUCTOP, but the bitstring
 211        data is just made into a bitstring constant when the operation
 212        is executed.  */
 213     OP_BITSTRING,
 214
 215     /* OP_ARRAY creates an array constant out of the following subexpressions.
 216        It is followed by two exp_elements, the first containing an integer
 217        that is the lower bound of the array and the second containing another
 218        integer that is the upper bound of the array.  The second integer is
 219        followed by a repeat of OP_ARRAY, making four exp_elements total.
 220        The bounds are used to compute the number of following subexpressions
 221        to consume, as well as setting the bounds in the created array constant.
 222        The type of the elements is taken from the type of the first subexp,
 223        and they must all match. */
 224     OP_ARRAY,
 225
 226     /* UNOP_CAST is followed by a type pointer in the next exp_element.
 227        With another UNOP_CAST at the end, this makes three exp_elements.
 228        It casts the value of the following subexpression.  */
 229     UNOP_CAST,
 230
 231     /* UNOP_MEMVAL is followed by a type pointer in the next exp_element
 232        With another UNOP_MEMVAL at the end, this makes three exp_elements.
 233        It casts the contents of the word addressed by the value of the
 234        following subexpression.  */
 235     UNOP_MEMVAL,
 236
 237     /* UNOP_MEMVAL_TLS is followed by a `struct objfile' pointer in the next
 238        exp_element and a type pointer in the following exp_element.
 239        With another UNOP_MEMVAL_TLS at the end, this makes four exp_elements.
 240        It casts the contents of the word offsetted by the value of the
 241        following subexpression from the TLS specified by `struct objfile'.  */
 242     UNOP_MEMVAL_TLS,
 243
 244     /* UNOP_... operate on one value from a following subexpression
 245        and replace it with a result.  They take no immediate arguments.  */
 246
 247     UNOP_NEG,                   /* Unary - */
 248     UNOP_LOGICAL_NOT,           /* Unary ! */
 249     UNOP_COMPLEMENT,            /* Unary ~ */
 250     UNOP_IND,                   /* Unary * */
 251     UNOP_ADDR,                  /* Unary & */
 252     UNOP_PREINCREMENT,          /* ++ before an expression */
 253     UNOP_POSTINCREMENT,         /* ++ after an expression */
 254     UNOP_PREDECREMENT,          /* -- before an expression */
 255     UNOP_POSTDECREMENT,         /* -- after an expression */
 256     UNOP_SIZEOF,                /* Unary sizeof (followed by expression) */
 257
 258     UNOP_PLUS,                  /* Unary plus */
 259
 260     UNOP_CAP,                   /* Modula-2 standard (unary) procedures */
 261     UNOP_CHR,
 262     UNOP_ORD,
 263     UNOP_ABS,
 264     UNOP_FLOAT,
 265     UNOP_HIGH,
 266     UNOP_MAX,
 267     UNOP_MIN,
 268     UNOP_ODD,
 269     UNOP_TRUNC,
 270
 271     /* (The deleted) Chill builtin functions.  */
 272     UNOP_LOWER, UNOP_UPPER, UNOP_LENGTH, UNOP_CARD, UNOP_CHMAX, UNOP_CHMIN,
 273
 274     OP_BOOL,                    /* Modula-2 builtin BOOLEAN type */
 275     OP_M2_STRING,               /* Modula-2 string constants */
 276
 277     /* STRUCTOP_... operate on a value from a following subexpression
 278        by extracting a structure component specified by a string
 279        that appears in the following exp_elements (as many as needed).
 280        STRUCTOP_STRUCT is used for "." and STRUCTOP_PTR for "->".
 281        They differ only in the error message given in case the value is
 282        not suitable or the structure component specified is not found.
 283
 284        The length of the string follows the opcode, followed by
 285        BYTES_TO_EXP_ELEM(length) elements containing the data of the
 286        string, followed by the length again and the opcode again.  */
 287
 288     STRUCTOP_STRUCT,
 289     STRUCTOP_PTR,
 290
 291     /* C++: OP_THIS is just a placeholder for the class instance variable.
 292        It just comes in a tight (OP_THIS, OP_THIS) pair.  */
 293     OP_THIS,
 294
 295     /* Objective-C: OP_OBJC_SELF is just a placeholder for the class instance
 296        variable.  It just comes in a tight (OP_OBJC_SELF, OP_OBJC_SELF) pair.  */
 297     OP_OBJC_SELF,
 298
 299     /* Objective C: "@selector" pseudo-operator */
 300     OP_OBJC_SELECTOR,
 301
 302     /* OP_SCOPE surrounds a type name and a field name.  The type
 303        name is encoded as one element, but the field name stays as
 304        a string, which, of course, is variable length.  */
 305     OP_SCOPE,
 306
 307     /* Used to represent named structure field values in brace
 308        initializers (or tuples as they are called in (the deleted)
 309        Chill).
 310
 311        The gcc C syntax is NAME:VALUE or .NAME=VALUE, the (the
 312        deleted) Chill syntax is .NAME:VALUE.  Multiple labels (as in
 313        the (the deleted) Chill syntax .NAME1,.NAME2:VALUE) is
 314        represented as if it were .NAME1:(.NAME2:VALUE) (though that is
 315        not valid (the deleted) Chill syntax).
 316
 317        The NAME is represented as for STRUCTOP_STRUCT;  VALUE follows. */
 318     OP_LABELED,
 319
 320     /* OP_TYPE is for parsing types, and used with the "ptype" command
 321        so we can look up types that are qualified by scope, either with
 322        the GDB "::" operator, or the Modula-2 '.' operator. */
 323     OP_TYPE,
 324
 325     /* An un-looked-up identifier. */
 326     OP_NAME,
 327
 328     /* An unparsed expression.  Used for Scheme (for now at least) */
 329     OP_EXPRSTRING,
 330
 331     /* An Objective C Foundation Class NSString constant */
 332     OP_OBJC_NSSTRING,
 333
 334     /* A F90 array range operator (for "exp:exp", "exp:", ":exp" and ":").  */
 335     OP_F90_RANGE,
 336
 337      /* First extension operator.  Individual language modules define
 338         extra operators they need as constants with values
 339         OP_LANGUAGE_SPECIFIC0 + k, for k >= 0, using a separate
 340         enumerated type definition:
 341            enum foo_extension_operator {
 342              BINOP_MOGRIFY = OP_EXTENDED0,
 343              BINOP_FROB,
 344              ...
 345            };      */
 346     OP_EXTENDED0,
 347
 348     /* Last possible extension operator.  Defined to provide an
 349        explicit and finite number of extended operators. */
 350     OP_EXTENDED_LAST = 0xff
 351     /* NOTE: Eventually, we expect to convert to an object-oriented
 352        formulation for expression operators that does away with the
 353        need for these extension operators, and indeed for this
 354        entire enumeration type.  Therefore, consider the OP_EXTENDED
 355        definitions to be a temporary measure. */
 356   };
 357
 358 union exp_element
 359   {
 360     enum exp_opcode opcode;
 361     struct symbol *symbol;
 362     LONGEST longconst;
 363     DOUBLEST doubleconst;
 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 expression *parse_expression_in_context (char *, int);
 393
 394 extern struct expression *parse_exp_1 (char **, struct block *, int);
 395
 396 /* The innermost context required by the stack and register variables
 397    we've encountered so far.  To use this, set it to NULL, then call
 398    parse_<whatever>, then look at it.  */
 399 extern struct block *innermost_block;
 400
 401 /* From eval.c */
 402
 403 /* Values of NOSIDE argument to eval_subexp.  */
 404
 405 enum noside
 406   {
 407     EVAL_NORMAL,
 408     EVAL_SKIP,                  /* Only effect is to increment pos.  */
 409     EVAL_AVOID_SIDE_EFFECTS     /* Don't modify any variables or
 410                                    call any functions.  The value
 411                                    returned will have the correct
 412                                    type, and will have an
 413                                    approximately correct lvalue
 414                                    type (inaccuracy: anything that is
 415                                    listed as being in a register in
 416                                    the function in which it was
 417                                    declared will be lval_register).  */
 418   };
 419
 420 extern struct value *evaluate_subexp_standard
 421   (struct type *, struct expression *, int *, enum noside);
 422
 423 /* From expprint.c */
 424
 425 extern void print_expression (struct expression *, struct ui_file *);
 426
 427 extern char *op_string (enum exp_opcode);
 428
 429 extern void dump_raw_expression (struct expression *, struct ui_file *, char *);
 430 extern void dump_prefix_expression (struct expression *, struct ui_file *);
 431
 432 #endif /* !defined (EXPRESSION_H) */