gdb/eval.c

   1 /* Evaluate expressions for GDB.
   2    Copyright 1986, 1987, 1989, 1991, 1992 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 #include "defs.h"
  21 #include "symtab.h"
  22 #include "gdbtypes.h"
  23 #include "value.h"
  24 #include "expression.h"
  25 #include "target.h"
  26 #include "frame.h"
  27
  28 /* Values of NOSIDE argument to eval_subexp.  */
  29 enum noside
  30 { EVAL_NORMAL,
  31   EVAL_SKIP,                    /* Only effect is to increment pos.  */
  32   EVAL_AVOID_SIDE_EFFECTS       /* Don't modify any variables or
  33                                    call any functions.  The value
  34                                    returned will have the correct
  35                                    type, and will have an
  36                                    approximately correct lvalue
  37                                    type (inaccuracy: anything that is
  38                                    listed as being in a register in
  39                                    the function in which it was
  40                                    declared will be lval_register).  */
  41 };
  42
  43 /* Prototypes for local functions. */
  44
  45 static value
  46 evaluate_subexp_for_sizeof PARAMS ((struct expression *, int *));
  47
  48 static value
  49 evaluate_subexp_with_coercion PARAMS ((struct expression *, int *,
  50                                        enum noside));
  51
  52 static value
  53 evaluate_subexp_for_address PARAMS ((struct expression *, int *,
  54                                      enum noside));
  55
  56 static value
  57 evaluate_subexp PARAMS ((struct type *, struct expression *, int *,
  58                          enum noside));
  59
  60 \f
  61 /* Parse the string EXP as a C expression, evaluate it,
  62    and return the result as a number.  */
  63
  64 CORE_ADDR
  65 parse_and_eval_address (exp)
  66      char *exp;
  67 {
  68   struct expression *expr = parse_expression (exp);
  69   register CORE_ADDR addr;
  70   register struct cleanup *old_chain =
  71       make_cleanup (free_current_contents, &expr);
  72
  73   addr = value_as_pointer (evaluate_expression (expr));
  74   do_cleanups (old_chain);
  75   return addr;
  76 }
  77
  78 /* Like parse_and_eval_address but takes a pointer to a char * variable
  79    and advanced that variable across the characters parsed.  */
  80
  81 CORE_ADDR
  82 parse_and_eval_address_1 (expptr)
  83      char **expptr;
  84 {
  85   struct expression *expr = parse_exp_1 (expptr, (struct block *)0, 0);
  86   register CORE_ADDR addr;
  87   register struct cleanup *old_chain =
  88       make_cleanup (free_current_contents, &expr);
  89
  90   addr = value_as_pointer (evaluate_expression (expr));
  91   do_cleanups (old_chain);
  92   return addr;
  93 }
  94
  95 value
  96 parse_and_eval (exp)
  97      char *exp;
  98 {
  99   struct expression *expr = parse_expression (exp);
 100   register value val;
 101   register struct cleanup *old_chain
 102     = make_cleanup (free_current_contents, &expr);
 103
 104   val = evaluate_expression (expr);
 105   do_cleanups (old_chain);
 106   return val;
 107 }
 108
 109 /* Parse up to a comma (or to a closeparen)
 110    in the string EXPP as an expression, evaluate it, and return the value.
 111    EXPP is advanced to point to the comma.  */
 112
 113 value
 114 parse_to_comma_and_eval (expp)
 115      char **expp;
 116 {
 117   struct expression *expr = parse_exp_1 (expp, (struct block *) 0, 1);
 118   register value val;
 119   register struct cleanup *old_chain
 120     = make_cleanup (free_current_contents, &expr);
 121
 122   val = evaluate_expression (expr);
 123   do_cleanups (old_chain);
 124   return val;
 125 }
 126 \f
 127 /* Evaluate an expression in internal prefix form
 128    such as is constructed by parse.y.
 129
 130    See expression.h for info on the format of an expression.  */
 131
 132 static value evaluate_subexp ();
 133 static value evaluate_subexp_for_address ();
 134 static value evaluate_subexp_for_sizeof ();
 135 static value evaluate_subexp_with_coercion ();
 136
 137 value
 138 evaluate_expression (exp)
 139      struct expression *exp;
 140 {
 141   int pc = 0;
 142   return evaluate_subexp (NULL_TYPE, exp, &pc, EVAL_NORMAL);
 143 }
 144
 145 /* Evaluate an expression, avoiding all memory references
 146    and getting a value whose type alone is correct.  */
 147
 148 value
 149 evaluate_type (exp)
 150      struct expression *exp;
 151 {
 152   int pc = 0;
 153   return evaluate_subexp (NULL_TYPE, exp, &pc, EVAL_AVOID_SIDE_EFFECTS);
 154 }
 155
 156 static value
 157 evaluate_subexp (expect_type, exp, pos, noside)
 158      struct type *expect_type;
 159      register struct expression *exp;
 160      register int *pos;
 161      enum noside noside;
 162 {
 163   enum exp_opcode op;
 164   int tem;
 165   register int pc, pc2, oldpos;
 166   register value arg1, arg2, arg3;
 167   struct type *type;
 168   int nargs;
 169   value *argvec;
 170
 171   pc = (*pos)++;
 172   op = exp->elts[pc].opcode;
 173
 174   switch (op)
 175     {
 176     case OP_SCOPE:
 177       tem = strlen (&exp->elts[pc + 2].string);
 178       (*pos) += 3 + ((tem + sizeof (union exp_element))
 179                      / sizeof (union exp_element));
 180       arg1 = value_struct_elt_for_reference (exp->elts[pc + 1].type,
 181                                              0,
 182                                              exp->elts[pc + 1].type,
 183                                              &exp->elts[pc + 2].string,
 184                                              expect_type);
 185       if (arg1 == NULL)
 186         error ("There is no field named %s", &exp->elts[pc + 2].string);
 187       return arg1;
 188
 189     case OP_LONG:
 190       (*pos) += 3;
 191       return value_from_longest (exp->elts[pc + 1].type,
 192                               exp->elts[pc + 2].longconst);
 193
 194     case OP_DOUBLE:
 195       (*pos) += 3;
 196       return value_from_double (exp->elts[pc + 1].type,
 197                                 exp->elts[pc + 2].doubleconst);
 198
 199     case OP_VAR_VALUE:
 200       (*pos) += 2;
 201       if (noside == EVAL_SKIP)
 202         goto nosideret;
 203       if (noside == EVAL_AVOID_SIDE_EFFECTS)
 204         {
 205           struct symbol * sym = exp->elts[pc + 1].symbol;
 206           enum lval_type lv;
 207
 208           switch (SYMBOL_CLASS (sym))
 209             {
 210             case LOC_CONST:
 211             case LOC_LABEL:
 212             case LOC_CONST_BYTES:
 213               lv = not_lval;
 214               break;
 215
 216             case LOC_REGISTER:
 217             case LOC_REGPARM:
 218               lv = lval_register;
 219               break;
 220
 221             default:
 222               lv = lval_memory;
 223               break;
 224             }
 225
 226           return value_zero (SYMBOL_TYPE (sym), lv);
 227         }
 228       else
 229         return value_of_variable (exp->elts[pc + 1].symbol);
 230
 231     case OP_LAST:
 232       (*pos) += 2;
 233       return
 234         access_value_history (longest_to_int (exp->elts[pc + 1].longconst));
 235
 236     case OP_REGISTER:
 237       (*pos) += 2;
 238       return value_of_register (longest_to_int (exp->elts[pc + 1].longconst));
 239
 240     case OP_INTERNALVAR:
 241       (*pos) += 2;
 242       return value_of_internalvar (exp->elts[pc + 1].internalvar);
 243
 244     case OP_STRING:
 245       tem = strlen (&exp->elts[pc + 1].string);
 246       (*pos) += 2 + ((tem + sizeof (union exp_element))
 247                      / sizeof (union exp_element));
 248       if (noside == EVAL_SKIP)
 249         goto nosideret;
 250       return value_string (&exp->elts[pc + 1].string, tem);
 251
 252     case TERNOP_COND:
 253       /* Skip third and second args to evaluate the first one.  */
 254       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 255       if (value_zerop (arg1))
 256         {
 257           evaluate_subexp (NULL_TYPE, exp, pos, EVAL_SKIP);
 258           return evaluate_subexp (NULL_TYPE, exp, pos, noside);
 259         }
 260       else
 261         {
 262           arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 263           evaluate_subexp (NULL_TYPE, exp, pos, EVAL_SKIP);
 264           return arg2;
 265         }
 266
 267     case OP_FUNCALL:
 268       (*pos) += 2;
 269       op = exp->elts[*pos].opcode;
 270       if (op == STRUCTOP_MEMBER || op == STRUCTOP_MPTR)
 271         {
 272           int fnptr;
 273
 274           nargs = longest_to_int (exp->elts[pc + 1].longconst) + 1;
 275           /* First, evaluate the structure into arg2 */
 276           pc2 = (*pos)++;
 277
 278           if (noside == EVAL_SKIP)
 279             goto nosideret;
 280
 281           if (op == STRUCTOP_MEMBER)
 282             {
 283               arg2 = evaluate_subexp_for_address (exp, pos, noside);
 284             }
 285           else
 286             {
 287               arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 288             }
 289
 290           /* If the function is a virtual function, then the
 291              aggregate value (providing the structure) plays
 292              its part by providing the vtable.  Otherwise,
 293              it is just along for the ride: call the function
 294              directly.  */
 295
 296           arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 297
 298           fnptr = longest_to_int (value_as_long (arg1));
 299           /* FIXME-tiemann: this is way obsolete.  */
 300           if (fnptr < 128)
 301             {
 302               struct type *basetype;
 303               int i, j;
 304               basetype = TYPE_TARGET_TYPE (VALUE_TYPE (arg2));
 305               basetype = TYPE_VPTR_BASETYPE (basetype);
 306               for (i = TYPE_NFN_FIELDS (basetype) - 1; i >= 0; i--)
 307                 {
 308                   struct fn_field *f = TYPE_FN_FIELDLIST1 (basetype, i);
 309                   /* If one is virtual, then all are virtual.  */
 310                   if (TYPE_FN_FIELD_VIRTUAL_P (f, 0))
 311                     for (j = TYPE_FN_FIELDLIST_LENGTH (basetype, i) - 1; j >= 0; --j)
 312                       if (TYPE_FN_FIELD_VOFFSET (f, j) == fnptr)
 313                         {
 314                           value vtbl;
 315                           value base = value_ind (arg2);
 316                           struct type *fntype = lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j));
 317
 318                           if (TYPE_VPTR_FIELDNO (basetype) < 0)
 319                             fill_in_vptr_fieldno (basetype);
 320
 321                           VALUE_TYPE (base) = basetype;
 322                           vtbl = value_field (base, TYPE_VPTR_FIELDNO (basetype));
 323                           VALUE_TYPE (vtbl) = lookup_pointer_type (fntype);
 324                           VALUE_TYPE (arg1) = builtin_type_int;
 325                           arg1 = value_subscript (vtbl, arg1);
 326                           VALUE_TYPE (arg1) = fntype;
 327                           goto got_it;
 328                         }
 329                 }
 330               if (i < 0)
 331                 error ("virtual function at index %d not found", fnptr);
 332             }
 333           else
 334             {
 335               VALUE_TYPE (arg1) = lookup_pointer_type (TYPE_TARGET_TYPE (VALUE_TYPE (arg1)));
 336             }
 337         got_it:
 338
 339           /* Now, say which argument to start evaluating from */
 340           tem = 2;
 341         }
 342       else if (op == STRUCTOP_STRUCT || op == STRUCTOP_PTR)
 343         {
 344           /* Hair for method invocations */
 345           int tem2;
 346
 347           nargs = longest_to_int (exp->elts[pc + 1].longconst) + 1;
 348           /* First, evaluate the structure into arg2 */
 349           pc2 = (*pos)++;
 350           tem2 = strlen (&exp->elts[pc2 + 1].string);
 351           *pos += 2 + (tem2 + sizeof (union exp_element)) / sizeof (union exp_element);
 352           if (noside == EVAL_SKIP)
 353             goto nosideret;
 354
 355           if (op == STRUCTOP_STRUCT)
 356             {
 357               arg2 = evaluate_subexp_for_address (exp, pos, noside);
 358             }
 359           else
 360             {
 361               arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 362             }
 363           /* Now, say which argument to start evaluating from */
 364           tem = 2;
 365         }
 366       else
 367         {
 368           nargs = longest_to_int (exp->elts[pc + 1].longconst);
 369           tem = 0;
 370         }
 371       argvec = (value *) alloca (sizeof (value) * (nargs + 2));
 372       for (; tem <= nargs; tem++)
 373         /* Ensure that array expressions are coerced into pointer objects. */
 374         argvec[tem] = evaluate_subexp_with_coercion (exp, pos, noside);
 375
 376       /* signal end of arglist */
 377       argvec[tem] = 0;
 378
 379       if (op == STRUCTOP_STRUCT || op == STRUCTOP_PTR)
 380         {
 381           int static_memfuncp;
 382           value temp = arg2;
 383
 384           argvec[1] = arg2;
 385           argvec[0] =
 386             value_struct_elt (&temp, argvec+1, &exp->elts[pc2 + 1].string,
 387                               &static_memfuncp,
 388                               op == STRUCTOP_STRUCT
 389                               ? "structure" : "structure pointer");
 390           if (VALUE_OFFSET (temp))
 391             {
 392               arg2 = value_from_longest (lookup_pointer_type (VALUE_TYPE (temp)),
 393                                       value_as_long (arg2)+VALUE_OFFSET (temp));
 394               argvec[1] = arg2;
 395             }
 396           if (static_memfuncp)
 397             {
 398               argvec[1] = argvec[0];
 399               nargs--;
 400               argvec++;
 401             }
 402         }
 403       else if (op == STRUCTOP_MEMBER || op == STRUCTOP_MPTR)
 404         {
 405           argvec[1] = arg2;
 406           argvec[0] = arg1;
 407         }
 408
 409       if (noside == EVAL_SKIP)
 410         goto nosideret;
 411       if (noside == EVAL_AVOID_SIDE_EFFECTS)
 412         {
 413           /* If the return type doesn't look like a function type, call an
 414              error.  This can happen if somebody tries to turn a variable into
 415              a function call. This is here because people often want to
 416              call, eg, strcmp, which gdb doesn't know is a function.  If
 417              gdb isn't asked for it's opinion (ie. through "whatis"),
 418              it won't offer it. */
 419
 420           struct type *ftype =
 421             TYPE_TARGET_TYPE (VALUE_TYPE (argvec[0]));
 422
 423           if (ftype)
 424             return allocate_value (TYPE_TARGET_TYPE (VALUE_TYPE (argvec[0])));
 425           else
 426             error ("Expression of type other than \"Function returning ...\" used as function");
 427         }
 428       return call_function_by_hand (argvec[0], nargs, argvec + 1);
 429
 430     case STRUCTOP_STRUCT:
 431       tem = strlen (&exp->elts[pc + 1].string);
 432       (*pos) += 2 + ((tem + sizeof (union exp_element))
 433                      / sizeof (union exp_element));
 434       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 435       if (noside == EVAL_SKIP)
 436         goto nosideret;
 437       if (noside == EVAL_AVOID_SIDE_EFFECTS)
 438         return value_zero (lookup_struct_elt_type (VALUE_TYPE (arg1),
 439                                                    &exp->elts[pc + 1].string,
 440                                                    1),
 441                            lval_memory);
 442       else
 443         {
 444           value temp = arg1;
 445           return value_struct_elt (&temp, (value *)0, &exp->elts[pc + 1].string,
 446                                    (int *) 0, "structure");
 447         }
 448
 449     case STRUCTOP_PTR:
 450       tem = strlen (&exp->elts[pc + 1].string);
 451       (*pos) += 2 + (tem + sizeof (union exp_element)) / sizeof (union exp_element);
 452       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 453       if (noside == EVAL_SKIP)
 454         goto nosideret;
 455       if (noside == EVAL_AVOID_SIDE_EFFECTS)
 456         return value_zero (lookup_struct_elt_type (TYPE_TARGET_TYPE
 457                                                    (VALUE_TYPE (arg1)),
 458                                                    &exp->elts[pc + 1].string,
 459                                                    1),
 460                            lval_memory);
 461       else
 462         {
 463           value temp = arg1;
 464           return value_struct_elt (&temp, (value *)0, &exp->elts[pc + 1].string,
 465                                    (int *) 0, "structure pointer");
 466         }
 467
 468     case STRUCTOP_MEMBER:
 469       arg1 = evaluate_subexp_for_address (exp, pos, noside);
 470       goto handle_pointer_to_member;
 471     case STRUCTOP_MPTR:
 472       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 473     handle_pointer_to_member:
 474       arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 475       if (noside == EVAL_SKIP)
 476         goto nosideret;
 477       if (TYPE_CODE (VALUE_TYPE (arg2)) != TYPE_CODE_PTR)
 478         goto bad_pointer_to_member;
 479       type = TYPE_TARGET_TYPE (VALUE_TYPE (arg2));
 480       if (TYPE_CODE (type) == TYPE_CODE_METHOD)
 481         error ("not implemented: pointer-to-method in pointer-to-member construct");
 482       if (TYPE_CODE (type) != TYPE_CODE_MEMBER)
 483         goto bad_pointer_to_member;
 484       /* Now, convert these values to an address.  */
 485       arg1 = value_cast (lookup_pointer_type (TYPE_DOMAIN_TYPE (type)),
 486                          arg1);
 487       arg3 = value_from_longest (lookup_pointer_type (TYPE_TARGET_TYPE (type)),
 488                                  value_as_long (arg1) + value_as_long (arg2));
 489       return value_ind (arg3);
 490     bad_pointer_to_member:
 491       error("non-pointer-to-member value used in pointer-to-member construct");
 492
 493     case BINOP_ASSIGN:
 494       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 495       arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
 496       if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
 497         return arg1;
 498       if (binop_user_defined_p (op, arg1, arg2))
 499         return value_x_binop (arg1, arg2, op, OP_NULL);
 500       else
 501         return value_assign (arg1, arg2);
 502
 503     case BINOP_ASSIGN_MODIFY:
 504       (*pos) += 2;
 505       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 506       arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
 507       if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
 508         return arg1;
 509       op = exp->elts[pc + 1].opcode;
 510       if (binop_user_defined_p (op, arg1, arg2))
 511         return value_x_binop (arg1, arg2, BINOP_ASSIGN_MODIFY, op);
 512       else if (op == BINOP_ADD)
 513         arg2 = value_add (arg1, arg2);
 514       else if (op == BINOP_SUB)
 515         arg2 = value_sub (arg1, arg2);
 516       else
 517         arg2 = value_binop (arg1, arg2, op);
 518       return value_assign (arg1, arg2);
 519
 520     case BINOP_ADD:
 521       arg1 = evaluate_subexp_with_coercion (exp, pos, noside);
 522       arg2 = evaluate_subexp_with_coercion (exp, pos, noside);
 523       if (noside == EVAL_SKIP)
 524         goto nosideret;
 525       if (binop_user_defined_p (op, arg1, arg2))
 526         return value_x_binop (arg1, arg2, op, OP_NULL);
 527       else
 528         return value_add (arg1, arg2);
 529
 530     case BINOP_SUB:
 531       arg1 = evaluate_subexp_with_coercion (exp, pos, noside);
 532       arg2 = evaluate_subexp_with_coercion (exp, pos, noside);
 533       if (noside == EVAL_SKIP)
 534         goto nosideret;
 535       if (binop_user_defined_p (op, arg1, arg2))
 536         return value_x_binop (arg1, arg2, op, OP_NULL);
 537       else
 538         return value_sub (arg1, arg2);
 539
 540     case BINOP_MUL:
 541     case BINOP_DIV:
 542     case BINOP_REM:
 543     case BINOP_LSH:
 544     case BINOP_RSH:
 545     case BINOP_LOGAND:
 546     case BINOP_LOGIOR:
 547     case BINOP_LOGXOR:
 548       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 549       arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 550       if (noside == EVAL_SKIP)
 551         goto nosideret;
 552       if (binop_user_defined_p (op, arg1, arg2))
 553         return value_x_binop (arg1, arg2, op, OP_NULL);
 554       else
 555         if (noside == EVAL_AVOID_SIDE_EFFECTS
 556             && (op == BINOP_DIV || op == BINOP_REM))
 557           return value_zero (VALUE_TYPE (arg1), not_lval);
 558       else
 559         return value_binop (arg1, arg2, op);
 560
 561     case BINOP_SUBSCRIPT:
 562       arg1 = evaluate_subexp_with_coercion (exp, pos, noside);
 563       arg2 = evaluate_subexp_with_coercion (exp, pos, noside);
 564       if (noside == EVAL_SKIP)
 565         goto nosideret;
 566       if (noside == EVAL_AVOID_SIDE_EFFECTS)
 567         return value_zero (TYPE_TARGET_TYPE (VALUE_TYPE (arg1)),
 568                            VALUE_LVAL (arg1));
 569
 570       if (binop_user_defined_p (op, arg1, arg2))
 571         return value_x_binop (arg1, arg2, op, OP_NULL);
 572       else
 573         return value_subscript (arg1, arg2);
 574
 575     case BINOP_AND:
 576       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 577       if (noside == EVAL_SKIP)
 578         {
 579           arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 580           goto nosideret;
 581         }
 582
 583       oldpos = *pos;
 584       arg2 = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_AVOID_SIDE_EFFECTS);
 585       *pos = oldpos;
 586
 587       if (binop_user_defined_p (op, arg1, arg2))
 588         {
 589           arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 590           return value_x_binop (arg1, arg2, op, OP_NULL);
 591         }
 592       else
 593         {
 594           tem = value_zerop (arg1);
 595           arg2 = evaluate_subexp (NULL_TYPE, exp, pos,
 596                                   (tem ? EVAL_SKIP : noside));
 597           return value_from_longest (builtin_type_int,
 598                                   (LONGEST) (!tem && !value_zerop (arg2)));
 599         }
 600
 601     case BINOP_OR:
 602       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 603       if (noside == EVAL_SKIP)
 604         {
 605           arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 606           goto nosideret;
 607         }
 608
 609       oldpos = *pos;
 610       arg2 = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_AVOID_SIDE_EFFECTS);
 611       *pos = oldpos;
 612
 613       if (binop_user_defined_p (op, arg1, arg2))
 614         {
 615           arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 616           return value_x_binop (arg1, arg2, op, OP_NULL);
 617         }
 618       else
 619         {
 620           tem = value_zerop (arg1);
 621           arg2 = evaluate_subexp (NULL_TYPE, exp, pos,
 622                                   (!tem ? EVAL_SKIP : noside));
 623           return value_from_longest (builtin_type_int,
 624                                   (LONGEST) (!tem || !value_zerop (arg2)));
 625         }
 626
 627     case BINOP_EQUAL:
 628       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 629       arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
 630       if (noside == EVAL_SKIP)
 631         goto nosideret;
 632       if (binop_user_defined_p (op, arg1, arg2))
 633         {
 634           return value_x_binop (arg1, arg2, op, OP_NULL);
 635         }
 636       else
 637         {
 638           tem = value_equal (arg1, arg2);
 639           return value_from_longest (builtin_type_int, (LONGEST) tem);
 640         }
 641
 642     case BINOP_NOTEQUAL:
 643       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 644       arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
 645       if (noside == EVAL_SKIP)
 646         goto nosideret;
 647       if (binop_user_defined_p (op, arg1, arg2))
 648         {
 649           return value_x_binop (arg1, arg2, op, OP_NULL);
 650         }
 651       else
 652         {
 653           tem = value_equal (arg1, arg2);
 654           return value_from_longest (builtin_type_int, (LONGEST) ! tem);
 655         }
 656
 657     case BINOP_LESS:
 658       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 659       arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
 660       if (noside == EVAL_SKIP)
 661         goto nosideret;
 662       if (binop_user_defined_p (op, arg1, arg2))
 663         {
 664           return value_x_binop (arg1, arg2, op, OP_NULL);
 665         }
 666       else
 667         {
 668           tem = value_less (arg1, arg2);
 669           return value_from_longest (builtin_type_int, (LONGEST) tem);
 670         }
 671
 672     case BINOP_GTR:
 673       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 674       arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
 675       if (noside == EVAL_SKIP)
 676         goto nosideret;
 677       if (binop_user_defined_p (op, arg1, arg2))
 678         {
 679           return value_x_binop (arg1, arg2, op, OP_NULL);
 680         }
 681       else
 682         {
 683           tem = value_less (arg2, arg1);
 684           return value_from_longest (builtin_type_int, (LONGEST) tem);
 685         }
 686
 687     case BINOP_GEQ:
 688       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 689       arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
 690       if (noside == EVAL_SKIP)
 691         goto nosideret;
 692       if (binop_user_defined_p (op, arg1, arg2))
 693         {
 694           return value_x_binop (arg1, arg2, op, OP_NULL);
 695         }
 696       else
 697         {
 698           tem = value_less (arg2, arg1) || value_equal (arg1, arg2);
 699           return value_from_longest (builtin_type_int, (LONGEST) tem);
 700         }
 701
 702     case BINOP_LEQ:
 703       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 704       arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
 705       if (noside == EVAL_SKIP)
 706         goto nosideret;
 707       if (binop_user_defined_p (op, arg1, arg2))
 708         {
 709           return value_x_binop (arg1, arg2, op, OP_NULL);
 710         }
 711       else
 712         {
 713           tem = value_less (arg1, arg2) || value_equal (arg1, arg2);
 714           return value_from_longest (builtin_type_int, (LONGEST) tem);
 715         }
 716
 717     case BINOP_REPEAT:
 718       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 719       arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 720       if (noside == EVAL_SKIP)
 721         goto nosideret;
 722       if (TYPE_CODE (VALUE_TYPE (arg2)) != TYPE_CODE_INT)
 723         error ("Non-integral right operand for \"@\" operator.");
 724       if (noside == EVAL_AVOID_SIDE_EFFECTS)
 725         return allocate_repeat_value (VALUE_TYPE (arg1),
 726                                       longest_to_int (value_as_long (arg2)));
 727       else
 728         return value_repeat (arg1, longest_to_int (value_as_long (arg2)));
 729
 730     case BINOP_COMMA:
 731       evaluate_subexp (NULL_TYPE, exp, pos, noside);
 732       return evaluate_subexp (NULL_TYPE, exp, pos, noside);
 733
 734     case UNOP_NEG:
 735       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 736       if (noside == EVAL_SKIP)
 737         goto nosideret;
 738       if (unop_user_defined_p (op, arg1))
 739         return value_x_unop (arg1, op);
 740       else
 741         return value_neg (arg1);
 742
 743     case UNOP_LOGNOT:
 744       /* C++: check for and handle destructor names.  */
 745       op = exp->elts[*pos].opcode;
 746
 747       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 748       if (noside == EVAL_SKIP)
 749         goto nosideret;
 750       if (unop_user_defined_p (UNOP_LOGNOT, arg1))
 751         return value_x_unop (arg1, UNOP_LOGNOT);
 752       else
 753         return value_lognot (arg1);
 754
 755     case UNOP_ZEROP:
 756       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 757       if (noside == EVAL_SKIP)
 758         goto nosideret;
 759       if (unop_user_defined_p (op, arg1))
 760         return value_x_unop (arg1, op);
 761       else
 762         return value_from_longest (builtin_type_int,
 763                                 (LONGEST) value_zerop (arg1));
 764
 765     case UNOP_IND:
 766       if (expect_type && TYPE_CODE (expect_type) == TYPE_CODE_PTR)
 767         expect_type = TYPE_TARGET_TYPE (expect_type);
 768       arg1 = evaluate_subexp (expect_type, exp, pos, noside);
 769       if (noside == EVAL_SKIP)
 770         goto nosideret;
 771       if (noside == EVAL_AVOID_SIDE_EFFECTS)
 772         {
 773           if (TYPE_CODE (VALUE_TYPE (arg1)) == TYPE_CODE_PTR
 774               || TYPE_CODE (VALUE_TYPE (arg1)) == TYPE_CODE_REF
 775               /* In C you can dereference an array to get the 1st elt.  */
 776               || TYPE_CODE (VALUE_TYPE (arg1)) == TYPE_CODE_ARRAY
 777               )
 778             return value_zero (TYPE_TARGET_TYPE (VALUE_TYPE (arg1)),
 779                                lval_memory);
 780           else if (TYPE_CODE (VALUE_TYPE (arg1)) == TYPE_CODE_INT)
 781             /* GDB allows dereferencing an int.  */
 782             return value_zero (builtin_type_int, lval_memory);
 783           else
 784             error ("Attempt to take contents of a non-pointer value.");
 785         }
 786       return value_ind (arg1);
 787
 788     case UNOP_ADDR:
 789       /* C++: check for and handle pointer to members.  */
 790
 791       op = exp->elts[*pos].opcode;
 792
 793       if (noside == EVAL_SKIP)
 794         {
 795           if (op == OP_SCOPE)
 796             {
 797               char *name = &exp->elts[pc+3].string;
 798               int temm = strlen (name);
 799               (*pos) += 2 + (temm + sizeof (union exp_element)) / sizeof (union exp_element);
 800             }
 801           else
 802             evaluate_subexp (expect_type, exp, pos, EVAL_SKIP);
 803           goto nosideret;
 804         }
 805
 806       return evaluate_subexp_for_address (exp, pos, noside);
 807
 808     case UNOP_SIZEOF:
 809       if (noside == EVAL_SKIP)
 810         {
 811           evaluate_subexp (NULL_TYPE, exp, pos, EVAL_SKIP);
 812           goto nosideret;
 813         }
 814       return evaluate_subexp_for_sizeof (exp, pos);
 815
 816     case UNOP_CAST:
 817       (*pos) += 2;
 818       arg1 = evaluate_subexp (expect_type, exp, pos, noside);
 819       if (noside == EVAL_SKIP)
 820         goto nosideret;
 821       return value_cast (exp->elts[pc + 1].type, arg1);
 822
 823     case UNOP_MEMVAL:
 824       (*pos) += 2;
 825       arg1 = evaluate_subexp (expect_type, exp, pos, noside);
 826       if (noside == EVAL_SKIP)
 827         goto nosideret;
 828       if (noside == EVAL_AVOID_SIDE_EFFECTS)
 829         return value_zero (exp->elts[pc + 1].type, lval_memory);
 830       else
 831         return value_at_lazy (exp->elts[pc + 1].type,
 832                               value_as_pointer (arg1));
 833
 834     case UNOP_PREINCREMENT:
 835       arg1 = evaluate_subexp (expect_type, exp, pos, noside);
 836       if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
 837         return arg1;
 838       else if (unop_user_defined_p (op, arg1))
 839         {
 840           return value_x_unop (arg1, op);
 841         }
 842       else
 843         {
 844           arg2 = value_add (arg1, value_from_longest (builtin_type_char,
 845                                                    (LONGEST) 1));
 846           return value_assign (arg1, arg2);
 847         }
 848
 849     case UNOP_PREDECREMENT:
 850       arg1 = evaluate_subexp (expect_type, exp, pos, noside);
 851       if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
 852         return arg1;
 853       else if (unop_user_defined_p (op, arg1))
 854         {
 855           return value_x_unop (arg1, op);
 856         }
 857       else
 858         {
 859           arg2 = value_sub (arg1, value_from_longest (builtin_type_char,
 860                                                    (LONGEST) 1));
 861           return value_assign (arg1, arg2);
 862         }
 863
 864     case UNOP_POSTINCREMENT:
 865       arg1 = evaluate_subexp (expect_type, exp, pos, noside);
 866       if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
 867         return arg1;
 868       else if (unop_user_defined_p (op, arg1))
 869         {
 870           return value_x_unop (arg1, op);
 871         }
 872       else
 873         {
 874           arg2 = value_add (arg1, value_from_longest (builtin_type_char,
 875                                                    (LONGEST) 1));
 876           value_assign (arg1, arg2);
 877           return arg1;
 878         }
 879
 880     case UNOP_POSTDECREMENT:
 881       arg1 = evaluate_subexp (expect_type, exp, pos, noside);
 882       if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
 883         return arg1;
 884       else if (unop_user_defined_p (op, arg1))
 885         {
 886           return value_x_unop (arg1, op);
 887         }
 888       else
 889         {
 890           arg2 = value_sub (arg1, value_from_longest (builtin_type_char,
 891                                                    (LONGEST) 1));
 892           value_assign (arg1, arg2);
 893           return arg1;
 894         }
 895
 896     case OP_THIS:
 897       (*pos) += 1;
 898       return value_of_this (1);
 899
 900     default:
 901       error ("internal error: I do not know how to evaluate what you gave me");
 902     }
 903
 904  nosideret:
 905   return value_from_longest (builtin_type_long, (LONGEST) 1);
 906 }
 907 \f
 908 /* Evaluate a subexpression of EXP, at index *POS,
 909    and return the address of that subexpression.
 910    Advance *POS over the subexpression.
 911    If the subexpression isn't an lvalue, get an error.
 912    NOSIDE may be EVAL_AVOID_SIDE_EFFECTS;
 913    then only the type of the result need be correct.  */
 914
 915 static value
 916 evaluate_subexp_for_address (exp, pos, noside)
 917      register struct expression *exp;
 918      register int *pos;
 919      enum noside noside;
 920 {
 921   enum exp_opcode op;
 922   register int pc;
 923   struct symbol *var;
 924
 925   pc = (*pos);
 926   op = exp->elts[pc].opcode;
 927
 928   switch (op)
 929     {
 930     case UNOP_IND:
 931       (*pos)++;
 932       return evaluate_subexp (NULL_TYPE, exp, pos, noside);
 933
 934     case UNOP_MEMVAL:
 935       (*pos) += 3;
 936       return value_cast (lookup_pointer_type (exp->elts[pc + 1].type),
 937                          evaluate_subexp (NULL_TYPE, exp, pos, noside));
 938
 939     case OP_VAR_VALUE:
 940       var = exp->elts[pc + 1].symbol;
 941
 942       /* C++: The "address" of a reference should yield the address
 943        * of the object pointed to. Let value_addr() deal with it. */
 944       if (TYPE_CODE (SYMBOL_TYPE (var)) == TYPE_CODE_REF)
 945         goto default_case;
 946
 947       (*pos) += 3;
 948       if (noside == EVAL_AVOID_SIDE_EFFECTS)
 949         {
 950           struct type *type =
 951             lookup_pointer_type (SYMBOL_TYPE (var));
 952           enum address_class sym_class = SYMBOL_CLASS (var);
 953
 954           if (sym_class == LOC_CONST
 955               || sym_class == LOC_CONST_BYTES
 956               || sym_class == LOC_REGISTER
 957               || sym_class == LOC_REGPARM)
 958             error ("Attempt to take address of register or constant.");
 959
 960         return
 961           value_zero (type, not_lval);
 962         }
 963       else
 964         return locate_var_value (var, (FRAME) 0);
 965
 966     default:
 967     default_case:
 968       if (noside == EVAL_AVOID_SIDE_EFFECTS)
 969         {
 970           value x = evaluate_subexp (NULL_TYPE, exp, pos, noside);
 971           if (VALUE_LVAL (x) == lval_memory)
 972             return value_zero (lookup_pointer_type (VALUE_TYPE (x)),
 973                                not_lval);
 974           else
 975             error ("Attempt to take address of non-lval");
 976         }
 977       return value_addr (evaluate_subexp (NULL_TYPE, exp, pos, noside));
 978     }
 979 }
 980
 981 /* Evaluate like `evaluate_subexp' except coercing arrays to pointers.
 982    When used in contexts where arrays will be coerced anyway,
 983    this is equivalent to `evaluate_subexp'
 984    but much faster because it avoids actually fetching array contents.  */
 985
 986 static value
 987 evaluate_subexp_with_coercion (exp, pos, noside)
 988      register struct expression *exp;
 989      register int *pos;
 990      enum noside noside;
 991 {
 992   register enum exp_opcode op;
 993   register int pc;
 994   register value val;
 995   struct symbol *var;
 996
 997   pc = (*pos);
 998   op = exp->elts[pc].opcode;
 999
1000   switch (op)
1001     {
1002     case OP_VAR_VALUE:
1003       var = exp->elts[pc + 1].symbol;
1004       if (TYPE_CODE (SYMBOL_TYPE (var)) == TYPE_CODE_ARRAY)
1005         {
1006           (*pos) += 3;
1007           val = locate_var_value (var, (FRAME) 0);
1008           return value_cast (lookup_pointer_type (TYPE_TARGET_TYPE (SYMBOL_TYPE (var))),
1009                              val);
1010         }
1011       default:
1012         return evaluate_subexp (NULL_TYPE, exp, pos, noside);
1013     }
1014 }
1015
1016 /* Evaluate a subexpression of EXP, at index *POS,
1017    and return a value for the size of that subexpression.
1018    Advance *POS over the subexpression.  */
1019
1020 static value
1021 evaluate_subexp_for_sizeof (exp, pos)
1022      register struct expression *exp;
1023      register int *pos;
1024 {
1025   enum exp_opcode op;
1026   register int pc;
1027   value val;
1028
1029   pc = (*pos);
1030   op = exp->elts[pc].opcode;
1031
1032   switch (op)
1033     {
1034       /* This case is handled specially
1035          so that we avoid creating a value for the result type.
1036          If the result type is very big, it's desirable not to
1037          create a value unnecessarily.  */
1038     case UNOP_IND:
1039       (*pos)++;
1040       val = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_AVOID_SIDE_EFFECTS);
1041       return value_from_longest (builtin_type_int, (LONGEST)
1042                       TYPE_LENGTH (TYPE_TARGET_TYPE (VALUE_TYPE (val))));
1043
1044     case UNOP_MEMVAL:
1045       (*pos) += 3;
1046       return value_from_longest (builtin_type_int,
1047                               (LONGEST) TYPE_LENGTH (exp->elts[pc + 1].type));
1048
1049     case OP_VAR_VALUE:
1050       (*pos) += 3;
1051       return value_from_longest (builtin_type_int,
1052          (LONGEST) TYPE_LENGTH (SYMBOL_TYPE (exp->elts[pc + 1].symbol)));
1053
1054     default:
1055       val = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_AVOID_SIDE_EFFECTS);
1056       return value_from_longest (builtin_type_int,
1057                               (LONGEST) TYPE_LENGTH (VALUE_TYPE (val)));
1058     }
1059 }
1060
1061 /* Parse a type expression in the string [P..P+LENGTH). */
1062
1063 struct type *
1064 parse_and_eval_type (p, length)
1065      char *p;
1066      int length;
1067 {
1068     char *tmp = (char *)alloca (length + 4);
1069     struct expression *expr;
1070     tmp[0] = '(';
1071     bcopy (p, tmp+1, length);
1072     tmp[length+1] = ')';
1073     tmp[length+2] = '0';
1074     tmp[length+3] = '\0';
1075     expr = parse_expression (tmp);
1076     if (expr->elts[0].opcode != UNOP_CAST)
1077         error ("Internal error in eval_type.");
1078     return expr->elts[1].type;
1079 }