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, 2009
   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     /* OP_COMPLEX takes a type in the following element, followed by another
 197        OP_COMPLEX, making three exp_elements.  It is followed by two double
 198        args, and converts them into a complex number of the given type. */
 199     OP_COMPLEX,
 200
 201     /* OP_STRING represents a string constant.
 202        Its format is the same as that of a STRUCTOP, but the string
 203        data is just made into a string constant when the operation
 204        is executed.  */
 205     OP_STRING,
 206
 207     /* OP_BITSTRING represents a packed bitstring constant.
 208        Its format is the same as that of a STRUCTOP, but the bitstring
 209        data is just made into a bitstring constant when the operation
 210        is executed.  */
 211     OP_BITSTRING,
 212
 213     /* OP_ARRAY creates an array constant out of the following subexpressions.
 214        It is followed by two exp_elements, the first containing an integer
 215        that is the lower bound of the array and the second containing another
 216        integer that is the upper bound of the array.  The second integer is
 217        followed by a repeat of OP_ARRAY, making four exp_elements total.
 218        The bounds are used to compute the number of following subexpressions
 219        to consume, as well as setting the bounds in the created array constant.
 220        The type of the elements is taken from the type of the first subexp,
 221        and they must all match. */
 222     OP_ARRAY,
 223
 224     /* UNOP_CAST is followed by a type pointer in the next exp_element.
 225        With another UNOP_CAST at the end, this makes three exp_elements.
 226        It casts the value of the following subexpression.  */
 227     UNOP_CAST,
 228
 229     /* UNOP_MEMVAL is followed by a type pointer in the next exp_element
 230        With another UNOP_MEMVAL at the end, this makes three exp_elements.
 231        It casts the contents of the word addressed by the value of the
 232        following subexpression.  */
 233     UNOP_MEMVAL,
 234
 235     /* UNOP_MEMVAL_TLS is followed by a `struct objfile' pointer in the next
 236        exp_element and a type pointer in the following exp_element.
 237        With another UNOP_MEMVAL_TLS at the end, this makes four exp_elements.
 238        It casts the contents of the word offsetted by the value of the
 239        following subexpression from the TLS specified by `struct objfile'.  */
 240     UNOP_MEMVAL_TLS,
 241
 242     /* UNOP_... operate on one value from a following subexpression
 243        and replace it with a result.  They take no immediate arguments.  */
 244
 245     UNOP_NEG,                   /* Unary - */
 246     UNOP_LOGICAL_NOT,           /* Unary ! */
 247     UNOP_COMPLEMENT,            /* Unary ~ */
 248     UNOP_IND,                   /* Unary * */
 249     UNOP_ADDR,                  /* Unary & */
 250     UNOP_PREINCREMENT,          /* ++ before an expression */
 251     UNOP_POSTINCREMENT,         /* ++ after an expression */
 252     UNOP_PREDECREMENT,          /* -- before an expression */
 253     UNOP_POSTDECREMENT,         /* -- after an expression */
 254     UNOP_SIZEOF,                /* Unary sizeof (followed by expression) */
 255
 256     UNOP_PLUS,                  /* Unary plus */
 257
 258     UNOP_CAP,                   /* Modula-2 standard (unary) procedures */
 259     UNOP_CHR,
 260     UNOP_ORD,
 261     UNOP_ABS,
 262     UNOP_FLOAT,
 263     UNOP_HIGH,
 264     UNOP_MAX,
 265     UNOP_MIN,
 266     UNOP_ODD,
 267     UNOP_TRUNC,
 268
 269     /* (The deleted) Chill builtin functions.  */
 270     UNOP_LOWER, UNOP_UPPER, UNOP_LENGTH, UNOP_CARD, UNOP_CHMAX, UNOP_CHMIN,
 271
 272     OP_BOOL,                    /* Modula-2 builtin BOOLEAN type */
 273     OP_M2_STRING,               /* Modula-2 string constants */
 274
 275     /* STRUCTOP_... operate on a value from a following subexpression
 276        by extracting a structure component specified by a string
 277        that appears in the following exp_elements (as many as needed).
 278        STRUCTOP_STRUCT is used for "." and STRUCTOP_PTR for "->".
 279        They differ only in the error message given in case the value is
 280        not suitable or the structure component specified is not found.
 281
 282        The length of the string follows the opcode, followed by
 283        BYTES_TO_EXP_ELEM(length) elements containing the data of the
 284        string, followed by the length again and the opcode again.  */
 285
 286     STRUCTOP_STRUCT,
 287     STRUCTOP_PTR,
 288
 289     /* C++: OP_THIS is just a placeholder for the class instance variable.
 290        It just comes in a tight (OP_THIS, OP_THIS) pair.  */
 291     OP_THIS,
 292
 293     /* Objective-C: OP_OBJC_SELF is just a placeholder for the class instance
 294        variable.  It just comes in a tight (OP_OBJC_SELF, OP_OBJC_SELF) pair.  */
 295     OP_OBJC_SELF,
 296
 297     /* Objective C: "@selector" pseudo-operator */
 298     OP_OBJC_SELECTOR,
 299
 300     /* OP_SCOPE surrounds a type name and a field name.  The type
 301        name is encoded as one element, but the field name stays as
 302        a string, which, of course, is variable length.  */
 303     OP_SCOPE,
 304
 305     /* Used to represent named structure field values in brace
 306        initializers (or tuples as they are called in (the deleted)
 307        Chill).
 308
 309        The gcc C syntax is NAME:VALUE or .NAME=VALUE, the (the
 310        deleted) Chill syntax is .NAME:VALUE.  Multiple labels (as in
 311        the (the deleted) Chill syntax .NAME1,.NAME2:VALUE) is
 312        represented as if it were .NAME1:(.NAME2:VALUE) (though that is
 313        not valid (the deleted) Chill syntax).
 314
 315        The NAME is represented as for STRUCTOP_STRUCT;  VALUE follows. */
 316     OP_LABELED,
 317
 318     /* OP_TYPE is for parsing types, and used with the "ptype" command
 319        so we can look up types that are qualified by scope, either with
 320        the GDB "::" operator, or the Modula-2 '.' operator. */
 321     OP_TYPE,
 322
 323     /* An un-looked-up identifier. */
 324     OP_NAME,
 325
 326     /* An Objective C Foundation Class NSString constant */
 327     OP_OBJC_NSSTRING,
 328
 329     /* A F90 array range operator (for "exp:exp", "exp:", ":exp" and ":").  */
 330     OP_F90_RANGE,
 331
 332     /* OP_DECFLOAT is followed by a type pointer in the next exp_element
 333        and a dec long constant value in the following exp_element.
 334        Then comes another OP_DECFLOAT.  */
 335     OP_DECFLOAT,
 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     gdb_byte decfloatconst[16];
 365     /* Really sizeof (union exp_element) characters (or less for the last
 366        element of a string).  */
 367     char string;
 368     struct type *type;
 369     struct internalvar *internalvar;
 370     struct block *block;
 371     struct objfile *objfile;
 372   };
 373
 374 struct expression
 375   {
 376     const struct language_defn *language_defn;  /* language it was entered in */
 377     struct gdbarch *gdbarch;  /* architecture it was parsed in */
 378     int nelts;
 379     union exp_element elts[1];
 380   };
 381
 382 /* Macros for converting between number of expression elements and bytes
 383    to store that many expression elements. */
 384
 385 #define EXP_ELEM_TO_BYTES(elements) \
 386     ((elements) * sizeof (union exp_element))
 387 #define BYTES_TO_EXP_ELEM(bytes) \
 388     (((bytes) + sizeof (union exp_element) - 1) / sizeof (union exp_element))
 389
 390 /* From parse.c */
 391
 392 extern struct expression *parse_expression (char *);
 393
 394 extern struct type *parse_field_expression (char *, char **);
 395
 396 extern struct expression *parse_exp_1 (char **, struct block *, int);
 397
 398 /* For use by parsers; set if we want to parse an expression and
 399    attempt to complete a field name.  */
 400 extern int in_parse_field;
 401
 402 /* The innermost context required by the stack and register variables
 403    we've encountered so far.  To use this, set it to NULL, then call
 404    parse_<whatever>, then look at it.  */
 405 extern struct block *innermost_block;
 406
 407 /* From eval.c */
 408
 409 /* Values of NOSIDE argument to eval_subexp.  */
 410
 411 enum noside
 412   {
 413     EVAL_NORMAL,
 414     EVAL_SKIP,                  /* Only effect is to increment pos.  */
 415     EVAL_AVOID_SIDE_EFFECTS     /* Don't modify any variables or
 416                                    call any functions.  The value
 417                                    returned will have the correct
 418                                    type, and will have an
 419                                    approximately correct lvalue
 420                                    type (inaccuracy: anything that is
 421                                    listed as being in a register in
 422                                    the function in which it was
 423                                    declared will be lval_register).  */
 424   };
 425
 426 extern struct value *evaluate_subexp_standard
 427   (struct type *, struct expression *, int *, enum noside);
 428
 429 /* From expprint.c */
 430
 431 extern void print_expression (struct expression *, struct ui_file *);
 432
 433 extern char *op_string (enum exp_opcode);
 434
 435 extern void dump_raw_expression (struct expression *, struct ui_file *, char *);
 436 extern void dump_prefix_expression (struct expression *, struct ui_file *);
 437
 438 #endif /* !defined (EXPRESSION_H) */