gdb/expression.h

   1 /* Definitions for expressions stored in reversed prefix form, for GDB.
   2    Copyright 1986, 1989, 1992, 1994 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., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 #if !defined (EXPRESSION_H)
  21 #define EXPRESSION_H 1
  22
  23 #ifdef __STDC__
  24 struct block;   /* Forward declaration for prototypes */
  25 #endif
  26
  27 /* Definitions for saved C expressions.  */
  28
  29 /* An expression is represented as a vector of union exp_element's.
  30    Each exp_element is an opcode, except that some opcodes cause
  31    the following exp_element to be treated as a long or double constant
  32    or as a variable.  The opcodes are obeyed, using a stack for temporaries.
  33    The value is left on the temporary stack at the end.  */
  34
  35 /* When it is necessary to include a string,
  36    it can occupy as many exp_elements as it needs.
  37    We find the length of the string using strlen,
  38    divide to find out how many exp_elements are used up,
  39    and skip that many.  Strings, like numbers, are indicated
  40    by the preceding opcode.  */
  41
  42 enum exp_opcode
  43 {
  44   /* Used when it's necessary to pass an opcode which will be ignored,
  45      or to catch uninitialized values.  */
  46   OP_NULL,
  47
  48 /* BINOP_... operate on two values computed by following subexpressions,
  49    replacing them by one result value.  They take no immediate arguments.  */
  50
  51   BINOP_ADD,            /* + */
  52   BINOP_SUB,            /* - */
  53   BINOP_MUL,            /* * */
  54   BINOP_DIV,            /* / */
  55   BINOP_REM,            /* % */
  56   BINOP_MOD,            /* mod (Knuth 1.2.4) */
  57   BINOP_LSH,            /* << */
  58   BINOP_RSH,            /* >> */
  59   BINOP_LOGICAL_AND,    /* && */
  60   BINOP_LOGICAL_OR,     /* || */
  61   BINOP_BITWISE_AND,    /* & */
  62   BINOP_BITWISE_IOR,    /* | */
  63   BINOP_BITWISE_XOR,    /* ^ */
  64   BINOP_EQUAL,          /* == */
  65   BINOP_NOTEQUAL,       /* != */
  66   BINOP_LESS,           /* < */
  67   BINOP_GTR,            /* > */
  68   BINOP_LEQ,            /* <= */
  69   BINOP_GEQ,            /* >= */
  70   BINOP_REPEAT,         /* @ */
  71   BINOP_ASSIGN,         /* = */
  72   BINOP_COMMA,          /* , */
  73   BINOP_SUBSCRIPT,      /* x[y] */
  74   BINOP_EXP,            /* Exponentiation */
  75
  76   /* C++.  */
  77
  78   BINOP_MIN,            /* <? */
  79   BINOP_MAX,            /* >? */
  80   BINOP_SCOPE,          /* :: */
  81
  82   /* STRUCTOP_MEMBER is used for pointer-to-member constructs.
  83      X . * Y translates into X STRUCTOP_MEMBER Y.  */
  84   STRUCTOP_MEMBER,
  85
  86   /* STRUCTOP_MPTR is used for pointer-to-member constructs
  87      when X is a pointer instead of an aggregate.  */
  88   STRUCTOP_MPTR,
  89
  90   /* end of C++.  */
  91
  92   /* For Modula-2 integer division DIV */
  93   BINOP_INTDIV,
  94
  95   BINOP_ASSIGN_MODIFY,  /* +=, -=, *=, and so on.
  96                            The following exp_element is another opcode,
  97                            a BINOP_, saying how to modify.
  98                            Then comes another BINOP_ASSIGN_MODIFY,
  99                            making three exp_elements in total.  */
 100
 101   /* Modula-2 standard (binary) procedures */
 102   BINOP_VAL,
 103   BINOP_INCL,
 104   BINOP_EXCL,
 105
 106   /* Concatenate two operands, such as character strings or bitstrings.
 107      If the first operand is a integer expression, then it means concatenate
 108      the second operand with itself that many times. */
 109   BINOP_CONCAT,
 110
 111   /* For Chill and Pascal. */
 112   BINOP_IN, /* Returns 1 iff ARG1 IN ARG2. */
 113
 114   /* This must be the highest BINOP_ value, for expprint.c.  */
 115   BINOP_END,
 116
 117   /* Operates on three values computed by following subexpressions.  */
 118   TERNOP_COND,          /* ?: */
 119
 120   /* A sub-string/sub-array.  Chill syntax:  OP1(OP2:OP3).
 121      Return elements OP2 through OP3 of OP1.  */
 122   TERNOP_SLICE,
 123
 124   /* A sub-string/sub-array.  Chill syntax:  OP1(OP2 UP OP3).
 125      Return OP3 elements of OP1, starting with element OP2. */
 126   TERNOP_SLICE_COUNT,
 127
 128   /* Multidimensional subscript operator, such as Modula-2 x[a,b,...].
 129      The dimensionality is encoded in the operator, like the number of
 130      function arguments in OP_FUNCALL, I.E. <OP><dimension><OP>.
 131      The value of the first following subexpression is subscripted
 132      by each of the next following subexpressions, one per dimension. */
 133    MULTI_SUBSCRIPT,
 134
 135   /* The OP_... series take immediate following arguments.
 136      After the arguments come another OP_... (the same one)
 137      so that the grouping can be recognized from the end.  */
 138
 139   /* OP_LONG is followed by a type pointer in the next exp_element
 140      and the long constant value in the following exp_element.
 141      Then comes another OP_LONG.
 142      Thus, the operation occupies four exp_elements.  */
 143   OP_LONG,
 144
 145   /* OP_DOUBLE is similar but takes a double constant instead of a long.  */
 146   OP_DOUBLE,
 147
 148   /* OP_VAR_VALUE takes one struct block * in the following element,
 149      and one struct symbol * in the following exp_element, followed by
 150      another OP_VAR_VALUE, making four exp_elements.  If the block is
 151      non-NULL, evaluate the symbol relative to the innermost frame
 152      executing in that block; if the block is NULL use the selected frame.  */
 153   OP_VAR_VALUE,
 154
 155   /* OP_LAST is followed by an integer in the next exp_element.
 156      The integer is zero for the last value printed,
 157      or it is the absolute number of a history element.
 158      With another OP_LAST at the end, this makes three exp_elements.  */
 159   OP_LAST,
 160
 161   /* OP_REGISTER is followed by an integer in the next exp_element.
 162      This is the number of a register to fetch (as an int).
 163      With another OP_REGISTER at the end, this makes three exp_elements.  */
 164   OP_REGISTER,
 165
 166   /* OP_INTERNALVAR is followed by an internalvar ptr in the next exp_element.
 167      With another OP_INTERNALVAR at the end, this makes three exp_elements.  */
 168   OP_INTERNALVAR,
 169
 170   /* OP_FUNCALL is followed by an integer in the next exp_element.
 171      The integer is the number of args to the function call.
 172      That many plus one values from following subexpressions
 173      are used, the first one being the function.
 174      The integer is followed by a repeat of OP_FUNCALL,
 175      making three exp_elements.  */
 176   OP_FUNCALL,
 177
 178   /* This is EXACTLY like OP_FUNCALL but is semantically different.
 179      In F77, array subscript expressions, substring expressions
 180      and function calls are  all exactly the same syntactically. They may
 181      only be dismabiguated at runtime.  Thus this operator, which
 182      indicates that we have found something of the form <name> ( <stuff> ) */
 183   OP_F77_UNDETERMINED_ARGLIST,
 184
 185   /* The following OP is a special one, it introduces a F77 complex
 186      literal. It is followed by exactly two args that are doubles.  */
 187   OP_COMPLEX,
 188
 189   /* OP_STRING represents a string constant.
 190      Its format is the same as that of a STRUCTOP, but the string
 191      data is just made into a string constant when the operation
 192      is executed.  */
 193   OP_STRING,
 194
 195   /* OP_BITSTRING represents a packed bitstring constant.
 196      Its format is the same as that of a STRUCTOP, but the bitstring
 197      data is just made into a bitstring constant when the operation
 198      is executed.  */
 199   OP_BITSTRING,
 200
 201   /* OP_ARRAY creates an array constant out of the following subexpressions.
 202      It is followed by two exp_elements, the first containing an integer
 203      that is the lower bound of the array and the second containing another
 204      integer that is the upper bound of the array.  The second integer is
 205      followed by a repeat of OP_ARRAY, making four exp_elements total.
 206      The bounds are used to compute the number of following subexpressions
 207      to consume, as well as setting the bounds in the created array constant.
 208      The type of the elements is taken from the type of the first subexp,
 209      and they must all match. */
 210   OP_ARRAY,
 211
 212   /* UNOP_CAST is followed by a type pointer in the next exp_element.
 213      With another UNOP_CAST at the end, this makes three exp_elements.
 214      It casts the value of the following subexpression.  */
 215   UNOP_CAST,
 216
 217   /* UNOP_MEMVAL is followed by a type pointer in the next exp_element
 218      With another UNOP_MEMVAL at the end, this makes three exp_elements.
 219      It casts the contents of the word addressed by the value of the
 220      following subexpression.  */
 221   UNOP_MEMVAL,
 222
 223   /* UNOP_... operate on one value from a following subexpression
 224      and replace it with a result.  They take no immediate arguments.  */
 225
 226   UNOP_NEG,             /* Unary - */
 227   UNOP_LOGICAL_NOT,     /* Unary ! */
 228   UNOP_COMPLEMENT,      /* Unary ~ */
 229   UNOP_IND,             /* Unary * */
 230   UNOP_ADDR,            /* Unary & */
 231   UNOP_PREINCREMENT,    /* ++ before an expression */
 232   UNOP_POSTINCREMENT,   /* ++ after an expression */
 233   UNOP_PREDECREMENT,    /* -- before an expression */
 234   UNOP_POSTDECREMENT,   /* -- after an expression */
 235   UNOP_SIZEOF,          /* Unary sizeof (followed by expression) */
 236
 237   UNOP_PLUS,            /* Unary plus */
 238
 239   UNOP_CAP,             /* Modula-2 standard (unary) procedures */
 240   UNOP_CHR,
 241   UNOP_ORD,
 242   UNOP_ABS,
 243   UNOP_FLOAT,
 244   UNOP_HIGH,
 245   UNOP_MAX,
 246   UNOP_MIN,
 247   UNOP_ODD,
 248   UNOP_TRUNC,
 249
 250   OP_BOOL,              /* Modula-2 builtin BOOLEAN type */
 251   OP_M2_STRING,         /* Modula-2 string constants */
 252
 253   /* STRUCTOP_... operate on a value from a following subexpression
 254      by extracting a structure component specified by a string
 255      that appears in the following exp_elements (as many as needed).
 256      STRUCTOP_STRUCT is used for "." and STRUCTOP_PTR for "->".
 257      They differ only in the error message given in case the value is
 258      not suitable or the structure component specified is not found.
 259
 260      The length of the string follows the opcode, followed by
 261      BYTES_TO_EXP_ELEM(length) elements containing the data of the
 262      string, followed by the length again and the opcode again.  */
 263
 264   STRUCTOP_STRUCT,
 265   STRUCTOP_PTR,
 266
 267   /* C++ */
 268   /* OP_THIS is just a placeholder for the class instance variable.
 269      It just comes in a tight (OP_THIS, OP_THIS) pair.  */
 270   OP_THIS,
 271
 272   /* OP_SCOPE surrounds a type name and a field name.  The type
 273      name is encoded as one element, but the field name stays as
 274      a string, which, of course, is variable length.  */
 275   OP_SCOPE,
 276
 277   /* Used to represent named structure field values in brace initializers
 278      (or tuples as they are called in Chill).
 279      The gcc C syntax is NAME:VALUE or .NAME=VALUE, the Chill syntax is
 280      .NAME:VALUE.  Multiple labels (as in the Chill syntax
 281      .NAME1,.NAME2:VALUE) is represented as if it were
 282      .NAME1:(.NAME2:VALUE) (though that is not valid Chill syntax).
 283
 284      The NAME is represented as for STRUCTOP_STRUCT;  VALUE follows. */
 285   OP_LABELED,
 286
 287   /* OP_TYPE is for parsing types, and used with the "ptype" command
 288      so we can look up types that are qualified by scope, either with
 289      the GDB "::" operator, or the Modula-2 '.' operator. */
 290   OP_TYPE
 291 };
 292
 293 union exp_element
 294 {
 295   enum exp_opcode opcode;
 296   struct symbol *symbol;
 297   LONGEST longconst;
 298   double doubleconst;
 299   /* Really sizeof (union exp_element) characters (or less for the last
 300      element of a string).  */
 301   char string;
 302   struct type *type;
 303   struct internalvar *internalvar;
 304   struct block *block;
 305 };
 306
 307 struct expression
 308 {
 309   const struct language_defn *language_defn;  /* language it was entered in */
 310   int nelts;
 311   union exp_element elts[1];
 312 };
 313
 314 /* Macros for converting between number of expression elements and bytes
 315    to store that many expression elements. */
 316
 317 #define EXP_ELEM_TO_BYTES(elements) \
 318     ((elements) * sizeof (union exp_element))
 319 #define BYTES_TO_EXP_ELEM(bytes) \
 320     (((bytes) + sizeof (union exp_element) - 1) / sizeof (union exp_element))
 321
 322 #include "value.h"
 323
 324 /* From parse.c */
 325
 326 extern struct expression *parse_expression PARAMS ((char *));
 327
 328 extern struct expression *parse_exp_1 PARAMS ((char **, struct block *, int));
 329
 330 /* The innermost context required by the stack and register variables
 331    we've encountered so far.  To use this, set it to NULL, then call
 332    parse_<whatever>, then look at it.  */
 333 extern struct block *innermost_block;
 334
 335 /* From eval.c */
 336
 337 /* Values of NOSIDE argument to eval_subexp.  */
 338
 339 enum noside
 340 {
 341   EVAL_NORMAL,
 342   EVAL_SKIP,                    /* Only effect is to increment pos.  */
 343   EVAL_AVOID_SIDE_EFFECTS       /* Don't modify any variables or
 344                                    call any functions.  The value
 345                                    returned will have the correct
 346                                    type, and will have an
 347                                    approximately correct lvalue
 348                                    type (inaccuracy: anything that is
 349                                    listed as being in a register in
 350                                    the function in which it was
 351                                    declared will be lval_register).  */
 352 };
 353
 354 extern struct value* evaluate_subexp_standard
 355 PARAMS ((struct type *, struct expression *, int*, enum noside));
 356
 357 extern value_ptr evaluate_subexp_with_coercion PARAMS ((struct expression *,
 358                                                         int *, enum noside));
 359
 360 /* From expprint.c */
 361
 362 extern void print_expression PARAMS ((struct expression *, GDB_FILE *));
 363
 364 extern char *op_string PARAMS ((enum exp_opcode));
 365
 366 /* To enable dumping of all parsed expressions in a human readable
 367    form, define DEBUG_EXPRESSIONS.  This is a compile time constant
 368    at the moment, since it's not clear that this feature is important
 369    enough to include by default. */
 370
 371 #ifdef DEBUG_EXPRESSIONS
 372 extern void dump_expression PARAMS ((struct expression *, GDB_FILE *, char *));
 373 #define DUMP_EXPRESSION(exp,file,note) dump_expression ((exp), (file), (note))
 374 #else
 375 #define DUMP_EXPRESSION(exp,file,note)  /* Null expansion */
 376 #endif  /* DEBUG_EXPRESSIONS */
 377
 378 #endif  /* !defined (EXPRESSION_H) */