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