smatch_math.c

   1 /*
   2  * smatch/smatch_math.c
   3  *
   4  * Copyright (C) 2010 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include "symbol.h"
  11 #include "smatch.h"
  12 #include "smatch_slist.h"
  13 #include "smatch_extra.h"
  14
  15 static sval_t _get_value(struct expression *expr, int *undefined, int implied);
  16 static sval_t _get_implied_value(struct expression *expr, int *undefined, int implied);
  17
  18 #define BOGUS 12345
  19
  20 static sval_t zero  = {.type = &int_ctype, {.value = 0} };
  21 static sval_t one   = {.type = &int_ctype, {.value = 1} };
  22 static sval_t bogus = {.type = &int_ctype, {.value = BOGUS} };
  23
  24 enum {
  25         NOTIMPLIED,
  26         IMPLIED,
  27         IMPLIED_MIN,
  28         IMPLIED_MAX,
  29         FUZZY_MAX,
  30         FUZZY_MIN,
  31         ABSOLUTE_MIN,
  32         ABSOLUTE_MAX,
  33         HARD_MAX,
  34 };
  35
  36 static int opposite_implied(int implied)
  37 {
  38         if (implied == IMPLIED_MIN)
  39                 return IMPLIED_MAX;
  40         if (implied == IMPLIED_MAX)
  41                 return IMPLIED_MIN;
  42         if (implied == FUZZY_MIN)
  43                 return FUZZY_MAX;
  44         if (implied == FUZZY_MAX)
  45                 return FUZZY_MIN;
  46         if (implied == ABSOLUTE_MIN)
  47                 return ABSOLUTE_MAX;
  48         if (implied == ABSOLUTE_MAX)
  49                 return ABSOLUTE_MIN;
  50         if (implied == HARD_MAX)  /* we don't have a hard min.  */
  51                 return NOTIMPLIED;
  52
  53         return implied;
  54 }
  55
  56 static int last_stmt_sval(struct statement *stmt, sval_t *sval)
  57 {
  58         struct expression *expr;
  59
  60         if (!stmt)
  61                 return 0;
  62
  63         stmt = last_ptr_list((struct ptr_list *)stmt->stmts);
  64         if (stmt->type != STMT_EXPRESSION)
  65                 return 0;
  66         expr = stmt->expression;
  67         if (!get_value(expr, sval))
  68                 return 0;
  69         return 1;
  70 }
  71
  72 static sval_t handle_expression_statement(struct expression *expr, int *undefined, int implied)
  73 {
  74         struct statement *stmt;
  75         sval_t ret;
  76
  77         stmt = get_expression_statement(expr);
  78         if (!last_stmt_sval(stmt, &ret)) {
  79                 *undefined = 1;
  80                 ret = bogus;
  81         }
  82
  83         return ret;
  84 }
  85
  86 static sval_t handle_ampersand(int *undefined, int implied)
  87 {
  88         sval_t ret;
  89
  90         ret.type = &ptr_ctype;
  91         ret.value = BOGUS;
  92
  93         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN)
  94                 return valid_ptr_min_sval;
  95         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX)
  96                 return valid_ptr_max_sval;
  97
  98         *undefined = 1;
  99         return ret;
 100 }
 101
 102 static sval_t handle_negate(struct expression *expr, int *undefined, int implied)
 103 {
 104         sval_t ret;
 105
 106         ret = sval_blank(expr->unop);
 107
 108         if (known_condition_true(expr->unop)) {
 109                 ret.value = 0;
 110                 return ret;
 111         }
 112
 113         if (implied == NOTIMPLIED) {
 114                 *undefined = 1;
 115                 return bogus;
 116         }
 117
 118         if (implied_condition_true(expr->unop)) {
 119                 ret.value = 0;
 120                 return ret;
 121         }
 122         if (implied_condition_false(expr->unop)) {
 123                 ret.value = 1;
 124                 return ret;
 125         }
 126         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN) {
 127                 ret.value = 0;
 128                 return ret;
 129         }
 130         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX) {
 131                 ret.value = 1;
 132                 return ret;
 133         }
 134         *undefined = 1;
 135         return bogus;
 136 }
 137
 138 static sval_t handle_preop(struct expression *expr, int *undefined, int implied)
 139 {
 140         sval_t ret;
 141
 142         switch (expr->op) {
 143         case '&':
 144                 ret = handle_ampersand(undefined, implied);
 145                 break;
 146         case '!':
 147                 ret = handle_negate(expr, undefined, implied);
 148                 break;
 149         case '~':
 150                 ret = _get_value(expr->unop, undefined, implied);
 151                 ret = sval_preop(ret, '~');
 152                 ret = sval_cast(get_type(expr->unop), ret);
 153                 break;
 154         case '-':
 155                 ret = _get_value(expr->unop, undefined, implied);
 156                 ret = sval_preop(ret, '-');
 157                 break;
 158         case '*':
 159                 ret = _get_implied_value(expr, undefined, implied);
 160                 break;
 161         case '(':
 162                 ret = handle_expression_statement(expr, undefined, implied);
 163                 break;
 164         default:
 165                 *undefined = 1;
 166                 ret = sval_blank(expr);
 167         }
 168         ret = sval_cast(get_type(expr), ret);
 169         return ret;
 170 }
 171
 172 static sval_t handle_divide(struct expression *expr, int *undefined, int implied)
 173 {
 174         sval_t left, right;
 175
 176         left = _get_value(expr->left, undefined, implied);
 177         right = _get_value(expr->right, undefined, opposite_implied(implied));
 178
 179         if (right.value == 0) {
 180                 *undefined = 1;
 181                 return bogus;
 182         }
 183
 184         return sval_binop(left, '/', right);
 185 }
 186
 187 static sval_t handle_subtract(struct expression *expr, int *undefined, int implied)
 188 {
 189         struct symbol *type;
 190         sval_t left, right, ret;
 191         int left_undefined = 0;
 192         int right_undefined = 0;
 193         int known_but_negative = 0;
 194         int comparison;
 195
 196         left = _get_value(expr->left, &left_undefined, implied);
 197         right = _get_value(expr->right, &right_undefined, opposite_implied(implied));
 198
 199         if (!left_undefined && !right_undefined) {
 200                 ret = sval_binop(left, '-', right);
 201                 if (sval_is_negative(ret))
 202                         known_but_negative = 1;
 203                 else
 204                         return ret;  /* best case scenario */
 205         }
 206
 207         comparison = get_comparison(expr->left, expr->right);
 208         if (!comparison)
 209                 goto bogus;
 210
 211         type = get_type(expr);
 212
 213         switch (comparison) {
 214         case '>':
 215         case SPECIAL_UNSIGNED_GT:
 216                 switch (implied) {
 217                 case IMPLIED_MIN:
 218                 case FUZZY_MIN:
 219                 case ABSOLUTE_MIN:
 220                         return sval_type_val(type, 1);
 221                 case IMPLIED_MAX:
 222                 case FUZZY_MAX:
 223                 case ABSOLUTE_MAX:
 224                         return _get_value(expr->left, undefined, implied);
 225                 }
 226                 break;
 227         case SPECIAL_GTE:
 228         case SPECIAL_UNSIGNED_GTE:
 229                 switch (implied) {
 230                 case IMPLIED_MIN:
 231                 case FUZZY_MIN:
 232                 case ABSOLUTE_MIN:
 233                         return sval_type_val(type, 0);
 234                 case IMPLIED_MAX:
 235                 case FUZZY_MAX:
 236                 case ABSOLUTE_MAX:
 237                         return _get_value(expr->left, undefined, implied);
 238                 }
 239                 break;
 240         }
 241
 242         if (known_but_negative)
 243                 return ret;
 244
 245 bogus:
 246         *undefined = 1;
 247         return bogus;
 248 }
 249
 250 static sval_t handle_mod(struct expression *expr, int *undefined, int implied)
 251 {
 252         sval_t left, right;
 253
 254         /* if we can't figure out the right side it's probably hopeless */
 255         right = _get_value(expr->right, undefined, implied);
 256         if (*undefined || right.value == 0) {
 257                 *undefined = 1;
 258                 return bogus;
 259         }
 260
 261         switch (implied) {
 262         case NOTIMPLIED:
 263         case IMPLIED:
 264                 left = _get_value(expr->left, undefined, implied);
 265                 if (!*undefined)
 266                         return sval_binop(left, '%', right);
 267                 return bogus;
 268         case IMPLIED_MIN:
 269         case FUZZY_MIN:
 270         case ABSOLUTE_MIN:
 271                 *undefined = 0;
 272                 return sval_type_val(get_type(expr->left), 0);
 273         case IMPLIED_MAX:
 274         case FUZZY_MAX:
 275         case ABSOLUTE_MAX:
 276                 *undefined = 0;
 277                 right = sval_cast(get_type(expr), right);
 278                 right.value--;
 279                 return right;
 280         }
 281         return bogus;
 282 }
 283
 284 static sval_t handle_binop(struct expression *expr, int *undefined, int implied)
 285 {
 286         struct symbol *type;
 287         sval_t left, right;
 288         sval_t ret = {.type = &int_ctype, {.value = 123456} };
 289         int local_undef = 0;
 290
 291         switch (expr->op) {
 292         case '%':
 293                 return handle_mod(expr, undefined, implied);
 294         case '&':
 295                 left = _get_value(expr->left, &local_undef, implied);
 296                 if (local_undef) {
 297                         if (implied == IMPLIED_MIN || implied == ABSOLUTE_MIN) {
 298                                 ret = sval_blank(expr->left);
 299                                 ret.value = 0;
 300                                 return ret;
 301                         }
 302                         if (implied != IMPLIED_MAX && implied != ABSOLUTE_MAX)
 303                                 *undefined = 1;
 304                         if (!get_absolute_max(expr->left, &left))
 305                                 *undefined = 1;
 306                 }
 307                 right = _get_value(expr->right, undefined, implied);
 308                 if (*undefined)
 309                         return bogus;
 310                 return sval_binop(left, '&', right);
 311
 312         case SPECIAL_RIGHTSHIFT:
 313                 left = _get_value(expr->left, &local_undef, implied);
 314                 if (local_undef) {
 315                         if (implied == IMPLIED_MIN || implied == ABSOLUTE_MIN) {
 316                                 ret = sval_blank(expr->left);
 317                                 ret.value = 0;
 318                                 return ret;
 319                         }
 320                         if (implied != IMPLIED_MAX && implied != ABSOLUTE_MAX)
 321                                 *undefined = 1;
 322                         if (!get_absolute_max(expr->left, &left))
 323                                 *undefined = 1;
 324                 }
 325                 right = _get_value(expr->right, undefined, implied);
 326                 if (*undefined)
 327                         return bogus;
 328                 return sval_binop(left, SPECIAL_RIGHTSHIFT, right);
 329         case '-':
 330                 return handle_subtract(expr, undefined, implied);
 331         }
 332
 333         left = _get_value(expr->left, undefined, implied);
 334         right = _get_value(expr->right, undefined, implied);
 335
 336         if (*undefined)
 337                 return bogus;
 338
 339         type = get_type(expr);
 340         left = sval_cast(type, left);
 341         right = sval_cast(type, right);
 342
 343         switch (implied) {
 344         case IMPLIED_MAX:
 345         case ABSOLUTE_MAX:
 346                 if (sval_binop_overflows(left, expr->op, right))
 347                         return sval_type_max(get_type(expr));
 348                 break;
 349         case HARD_MAX:
 350         case FUZZY_MAX:
 351                 if (sval_binop_overflows(left, expr->op, right)) {
 352                         *undefined = 1;
 353                         return bogus;
 354                 }
 355         }
 356
 357         switch (expr->op) {
 358         case '/':
 359                 return handle_divide(expr, undefined, implied);
 360         case '%':
 361                 if (right.value == 0) {
 362                         *undefined = 1;
 363                         return bogus;
 364                 } else {
 365                         return sval_binop(left, '%', right);
 366                 }
 367         default:
 368                 ret = sval_binop(left, expr->op, right);
 369         }
 370         return ret;
 371 }
 372
 373 static int do_comparison(struct expression *expr)
 374 {
 375         struct range_list *left_ranges = NULL;
 376         struct range_list *right_ranges = NULL;
 377         int poss_true, poss_false;
 378
 379         get_implied_rl(expr->left, &left_ranges);
 380         get_implied_rl(expr->right, &right_ranges);
 381
 382         poss_true = possibly_true_rl(left_ranges, expr->op, right_ranges);
 383         poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
 384
 385         free_rl(&left_ranges);
 386         free_rl(&right_ranges);
 387
 388         if (!poss_true && !poss_false)
 389                 return 0;
 390         if (poss_true && !poss_false)
 391                 return 1;
 392         if (!poss_true && poss_false)
 393                 return 2;
 394         return 3;
 395 }
 396
 397 static sval_t handle_comparison(struct expression *expr, int *undefined, int implied)
 398 {
 399         sval_t left, right;
 400         int res;
 401
 402         if (get_value(expr->left, &left) && get_value(expr->right, &right)) {
 403                 struct data_range tmp_left, tmp_right;
 404
 405                 tmp_left.min = left;
 406                 tmp_left.max = left;
 407                 tmp_right.min = right;
 408                 tmp_right.max = right;
 409                 if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
 410                         return one;
 411                 return zero;
 412         }
 413
 414         if (implied == NOTIMPLIED) {
 415                 *undefined = 1;
 416                 return bogus;
 417         }
 418
 419         res = do_comparison(expr);
 420         if (res == 1)
 421                 return one;
 422         if (res == 2)
 423                 return zero;
 424
 425         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN)
 426                 return zero;
 427         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX)
 428                 return one;
 429
 430         *undefined = 1;
 431         return bogus;
 432 }
 433
 434 static sval_t handle_logical(struct expression *expr, int *undefined, int implied)
 435 {
 436         sval_t left, right;
 437         int left_known = 0;
 438         int right_known = 0;
 439
 440         if (implied == NOTIMPLIED) {
 441                 if (get_value(expr->left, &left))
 442                         left_known = 1;
 443                 if (get_value(expr->right, &right))
 444                         right_known = 1;
 445         } else {
 446                 if (get_implied_value(expr->left, &left))
 447                         left_known = 1;
 448                 if (get_implied_value(expr->right, &right))
 449                         right_known = 1;
 450         }
 451
 452         switch (expr->op) {
 453         case SPECIAL_LOGICAL_OR:
 454                 if (left_known && left.value)
 455                         return one;
 456                 if (right_known && right.value)
 457                         return one;
 458                 if (left_known && right_known)
 459                         return zero;
 460                 break;
 461         case SPECIAL_LOGICAL_AND:
 462                 if (left_known && right_known) {
 463                         if (left.value && right.value)
 464                                 return one;
 465                         return zero;
 466                 }
 467                 break;
 468         default:
 469                 *undefined = 1;
 470                 return bogus;
 471         }
 472
 473         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN)
 474                 return zero;
 475         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX)
 476                 return one;
 477
 478         *undefined = 1;
 479         return bogus;
 480 }
 481
 482 static sval_t handle_conditional(struct expression *expr, int *undefined, int implied)
 483 {
 484         if (known_condition_true(expr->conditional))
 485                 return _get_value(expr->cond_true, undefined, implied);
 486         if (known_condition_false(expr->conditional))
 487                 return _get_value(expr->cond_false, undefined, implied);
 488
 489         if (implied == NOTIMPLIED) {
 490                 *undefined = 1;
 491                 return bogus;
 492         }
 493
 494         if (implied_condition_true(expr->conditional))
 495                 return _get_value(expr->cond_true, undefined, implied);
 496         if (implied_condition_false(expr->conditional))
 497                 return _get_value(expr->cond_false, undefined, implied);
 498
 499         *undefined = 1;
 500         return bogus;
 501 }
 502
 503 static int get_local_value(struct expression *expr, sval_t *sval, int implied)
 504 {
 505         switch (implied) {
 506         case NOTIMPLIED:
 507         case IMPLIED:
 508                 return 0;
 509         case IMPLIED_MIN:
 510         case FUZZY_MIN:
 511         case ABSOLUTE_MIN:
 512                 return get_local_min_helper(expr, sval);
 513         case ABSOLUTE_MAX:
 514         case HARD_MAX:
 515         case IMPLIED_MAX:
 516         case FUZZY_MAX:
 517                 return get_local_max_helper(expr, sval);
 518         }
 519         return 0;
 520 }
 521
 522 static int get_implied_value_helper(struct expression *expr, sval_t *sval, int implied)
 523 {
 524         struct smatch_state *state;
 525         struct symbol *sym;
 526         char *name;
 527
 528         /* fixme: this should return the casted value */
 529
 530         expr = strip_expr(expr);
 531
 532         if (get_value(expr, sval))
 533                 return 1;
 534
 535         name = expr_to_var_sym(expr, &sym);
 536         if (!name)
 537                 return 0;
 538         *sval = sval_blank(expr);
 539         state = get_state(SMATCH_EXTRA, name, sym);
 540         free_string(name);
 541         if (!state || !state->data)
 542                 return get_local_value(expr, sval, implied);
 543         if (implied == IMPLIED) {
 544                 if (estate_get_single_value(state, sval))
 545                         return 1;
 546                 return 0;
 547         }
 548         if (implied == HARD_MAX) {
 549                 if (estate_get_hard_max(state, sval))
 550                         return 1;
 551                 return 0;
 552         }
 553         if (implied == IMPLIED_MAX || implied == ABSOLUTE_MAX) {
 554                 *sval = estate_max(state);
 555                 return 1;
 556         }
 557         *sval = estate_min(state);
 558         return 1;
 559 }
 560
 561 static int get_fuzzy_max_helper(struct expression *expr, sval_t *max)
 562 {
 563         struct sm_state *sm;
 564         struct sm_state *tmp;
 565         sval_t sval;
 566
 567         if (get_hard_max(expr, &sval)) {
 568                 *max = sval;
 569                 return 1;
 570         }
 571
 572         sm = get_sm_state_expr(SMATCH_EXTRA, expr);
 573         if (!sm)
 574                 return 0;
 575
 576         sval = sval_type_min(estate_type(sm->state));
 577         FOR_EACH_PTR(sm->possible, tmp) {
 578                 sval_t new_min;
 579
 580                 new_min = estate_min(tmp->state);
 581                 if (sval_cmp(new_min, sval) > 0)
 582                         sval = new_min;
 583         } END_FOR_EACH_PTR(tmp);
 584
 585         if (sval_is_min(sval))
 586                 return 0;
 587         if (sval.value == sval_type_min(sval.type).value + 1)  /* it's common to be on off */
 588                 return 0;
 589
 590         *max = sval_cast(get_type(expr), sval);
 591         return 1;
 592 }
 593
 594 static int get_fuzzy_min_helper(struct expression *expr, sval_t *min)
 595 {
 596         struct sm_state *sm;
 597         struct sm_state *tmp;
 598         sval_t sval;
 599
 600         sm = get_sm_state_expr(SMATCH_EXTRA, expr);
 601         if (!sm)
 602                 return 0;
 603
 604         if (!sval_is_min(estate_min(sm->state))) {
 605                 *min = estate_min(sm->state);
 606                 return 1;
 607         }
 608
 609         sval = sval_type_max(estate_type(sm->state));
 610         FOR_EACH_PTR(sm->possible, tmp) {
 611                 sval_t new_max;
 612
 613                 new_max = estate_max(tmp->state);
 614                 if (sval_cmp(new_max, sval) < 0)
 615                         sval = new_max;
 616         } END_FOR_EACH_PTR(tmp);
 617
 618         if (sval_is_max(sval))
 619                 return 0;
 620         *min = sval_cast(get_type(expr), sval);
 621         return 1;
 622 }
 623
 624 static sval_t _get_implied_value(struct expression *expr, int *undefined, int implied)
 625 {
 626         sval_t ret;
 627
 628         ret = sval_blank(expr);
 629
 630         switch (implied) {
 631         case IMPLIED:
 632         case IMPLIED_MAX:
 633         case IMPLIED_MIN:
 634         case HARD_MAX:
 635         case ABSOLUTE_MIN:
 636         case ABSOLUTE_MAX:
 637                 if (!get_implied_value_helper(expr, &ret, implied))
 638                         *undefined = 1;
 639                 break;
 640         case FUZZY_MAX:
 641                 if (!get_fuzzy_max_helper(expr, &ret))
 642                         *undefined = 1;
 643                 break;
 644         case FUZZY_MIN:
 645                 if (!get_fuzzy_min_helper(expr, &ret))
 646                         *undefined = 1;
 647                 break;
 648         default:
 649                 *undefined = 1;
 650         }
 651         return ret;
 652 }
 653
 654 static int get_const_value(struct expression *expr, sval_t *sval)
 655 {
 656         struct symbol *sym;
 657         sval_t right;
 658
 659         if (expr->type != EXPR_SYMBOL || !expr->symbol)
 660                 return 0;
 661         sym = expr->symbol;
 662         if (!(sym->ctype.modifiers & MOD_CONST))
 663                 return 0;
 664         if (get_value(sym->initializer, &right)) {
 665                 *sval = sval_cast(get_type(expr), right);
 666                 return 1;
 667         }
 668         return 0;
 669 }
 670
 671 static sval_t handle_sizeof(struct expression *expr)
 672 {
 673         struct symbol *sym;
 674         sval_t ret;
 675
 676         ret = sval_blank(expr);
 677         sym = expr->cast_type;
 678         if (!sym) {
 679                 sym = evaluate_expression(expr->cast_expression);
 680                 /*
 681                  * Expressions of restricted types will possibly get
 682                  * promoted - check that here
 683                  */
 684                 if (is_restricted_type(sym)) {
 685                         if (sym->bit_size < bits_in_int)
 686                                 sym = &int_ctype;
 687                 } else if (is_fouled_type(sym)) {
 688                         sym = &int_ctype;
 689                 }
 690         }
 691         examine_symbol_type(sym);
 692
 693         ret.type = size_t_ctype;
 694         if (sym->bit_size <= 0) /* sizeof(void) */
 695                 ret.value = 1;
 696         else
 697                 ret.value = bits_to_bytes(sym->bit_size);
 698
 699         return ret;
 700 }
 701
 702 static sval_t _get_value(struct expression *expr, int *undefined, int implied)
 703 {
 704         sval_t ret;
 705
 706         if (!expr) {
 707                 *undefined = 1;
 708                 return bogus;
 709         }
 710         if (*undefined)
 711                 return bogus;
 712
 713         expr = strip_parens(expr);
 714
 715         switch (expr->type) {
 716         case EXPR_VALUE:
 717                 ret = sval_from_val(expr, expr->value);
 718                 break;
 719         case EXPR_PREOP:
 720                 ret = handle_preop(expr, undefined, implied);
 721                 break;
 722         case EXPR_POSTOP:
 723                 ret = _get_value(expr->unop, undefined, implied);
 724                 break;
 725         case EXPR_CAST:
 726         case EXPR_FORCE_CAST:
 727         case EXPR_IMPLIED_CAST:
 728                 ret = _get_value(expr->cast_expression, undefined, implied);
 729                 ret = sval_cast(get_type(expr), ret);
 730                 break;
 731         case EXPR_BINOP:
 732                 ret = handle_binop(expr, undefined, implied);
 733                 break;
 734         case EXPR_COMPARE:
 735                 ret = handle_comparison(expr, undefined, implied);
 736                 break;
 737         case EXPR_LOGICAL:
 738                 ret = handle_logical(expr, undefined, implied);
 739                 break;
 740         case EXPR_PTRSIZEOF:
 741         case EXPR_SIZEOF:
 742                 ret = handle_sizeof(expr);
 743                 break;
 744         case EXPR_SYMBOL:
 745                 if (get_const_value(expr, &ret)) {
 746                         break;
 747                 }
 748                 ret = _get_implied_value(expr, undefined, implied);
 749                 break;
 750         case EXPR_SELECT:
 751         case EXPR_CONDITIONAL:
 752                 ret = handle_conditional(expr, undefined, implied);
 753                 break;
 754         default:
 755                 ret = _get_implied_value(expr, undefined, implied);
 756         }
 757         if (*undefined)
 758                 return bogus;
 759         return ret;
 760 }
 761
 762 /* returns 1 if it can get a value literal or else returns 0 */
 763 int get_value(struct expression *expr, sval_t *sval)
 764 {
 765         int undefined = 0;
 766         sval_t ret;
 767
 768         ret = _get_value(expr, &undefined, NOTIMPLIED);
 769         if (undefined)
 770                 return 0;
 771         *sval = ret;
 772         return 1;
 773 }
 774
 775 int get_implied_value(struct expression *expr, sval_t *sval)
 776 {
 777         int undefined = 0;
 778         sval_t ret;
 779
 780         ret =  _get_value(expr, &undefined, IMPLIED);
 781         if (undefined)
 782                 return 0;
 783         *sval = ret;
 784         return 1;
 785 }
 786
 787 int get_implied_min(struct expression *expr, sval_t *sval)
 788 {
 789         int undefined = 0;
 790         sval_t ret;
 791
 792         ret =  _get_value(expr, &undefined, IMPLIED_MIN);
 793         if (undefined)
 794                 return 0;
 795         *sval = ret;
 796         return 1;
 797 }
 798
 799 int get_implied_max(struct expression *expr, sval_t *sval)
 800 {
 801         int undefined = 0;
 802         sval_t ret;
 803
 804         ret =  _get_value(expr, &undefined, IMPLIED_MAX);
 805         if (undefined)
 806                 return 0;
 807         *sval = ret;
 808         return 1;
 809 }
 810
 811 int get_implied_rl(struct expression *expr, struct range_list **rl)
 812 {
 813         sval_t sval;
 814         struct smatch_state *state;
 815         sval_t min, max;
 816         int min_known = 0;
 817         int max_known = 0;
 818
 819         *rl = NULL;
 820
 821         expr = strip_parens(expr);
 822         if (!expr)
 823                 return 0;
 824
 825         state = get_state_expr(SMATCH_EXTRA, expr);
 826         if (state) {
 827                 *rl = clone_rl(estate_rl(state));
 828                 return 1;
 829         }
 830
 831         if (expr->type == EXPR_CALL) {
 832                 if (get_implied_return(expr, rl))
 833                         return 1;
 834                 *rl = db_return_vals(expr);
 835                 if (*rl)
 836                         return 1;
 837                 return 0;
 838         }
 839
 840         if (get_implied_value(expr, &sval)) {
 841                 add_range(rl, sval, sval);
 842                 return 1;
 843         }
 844
 845         if (get_local_rl(expr, rl))
 846                 return 1;
 847
 848         min_known = get_implied_min(expr, &min);
 849         max_known = get_implied_max(expr, &max);
 850         if (!min_known && !max_known)
 851                 return 0;
 852         if (!min_known)
 853                 get_absolute_min(expr, &min);
 854         if (!max_known)
 855                 get_absolute_max(expr, &max);
 856
 857         *rl = alloc_rl(min, max);
 858         return 1;
 859 }
 860
 861 int get_hard_max(struct expression *expr, sval_t *sval)
 862 {
 863         int undefined = 0;
 864         sval_t ret;
 865
 866         ret =  _get_value(expr, &undefined, HARD_MAX);
 867         if (undefined)
 868                 return 0;
 869         *sval = ret;
 870         return 1;
 871 }
 872
 873 int get_fuzzy_min(struct expression *expr, sval_t *sval)
 874 {
 875         int undefined = 0;
 876         sval_t ret;
 877
 878         ret =  _get_value(expr, &undefined, FUZZY_MIN);
 879         if (undefined)
 880                 return 0;
 881         *sval = ret;
 882         return 1;
 883 }
 884
 885 int get_fuzzy_max(struct expression *expr, sval_t *sval)
 886 {
 887         int undefined = 0;
 888         sval_t ret;
 889
 890         ret =  _get_value(expr, &undefined, FUZZY_MAX);
 891         if (undefined)
 892                 return 0;
 893         if (ret.uvalue > INT_MAX - 10000)
 894                 return 0;
 895         *sval = ret;
 896         return 1;
 897 }
 898
 899 int get_absolute_min(struct expression *expr, sval_t *sval)
 900 {
 901         int undefined = 0;
 902         struct symbol *type;
 903
 904         type = get_type(expr);
 905         if (!type)
 906                 type = &llong_ctype;  // FIXME: this is wrong but places assume get type can't fail.
 907         *sval =  _get_value(expr, &undefined, ABSOLUTE_MIN);
 908         if (undefined) {
 909                 *sval = sval_type_min(type);
 910                 return 1;
 911         }
 912
 913         if (sval_cmp(*sval, sval_type_min(type)) < 0)
 914                 *sval = sval_type_min(type);
 915         return 1;
 916 }
 917
 918 int get_absolute_max(struct expression *expr, sval_t *sval)
 919 {
 920         int undefined = 0;
 921         struct symbol *type;
 922
 923         type = get_type(expr);
 924         if (!type)
 925                 type = &llong_ctype;
 926         *sval = _get_value(expr, &undefined, ABSOLUTE_MAX);
 927         if (undefined) {
 928                 *sval = sval_type_max(type);
 929                 return 1;
 930         }
 931
 932         if (sval_cmp(sval_type_max(type), *sval) < 0)
 933                 *sval = sval_type_max(type);
 934         return 1;
 935 }
 936
 937 int known_condition_true(struct expression *expr)
 938 {
 939         sval_t tmp;
 940
 941         if (!expr)
 942                 return 0;
 943
 944         if (get_value(expr, &tmp) && tmp.value)
 945                 return 1;
 946
 947         return 0;
 948 }
 949
 950 int known_condition_false(struct expression *expr)
 951 {
 952         if (!expr)
 953                 return 0;
 954
 955         if (is_zero(expr))
 956                 return 1;
 957
 958         if (expr->type == EXPR_CALL) {
 959                 if (sym_name_is("__builtin_constant_p", expr->fn))
 960                         return 1;
 961         }
 962         return 0;
 963 }
 964
 965 int implied_condition_true(struct expression *expr)
 966 {
 967         sval_t tmp;
 968
 969         if (!expr)
 970                 return 0;
 971
 972         if (known_condition_true(expr))
 973                 return 1;
 974         if (get_implied_value(expr, &tmp) && tmp.value)
 975                 return 1;
 976
 977         if (expr->type == EXPR_POSTOP)
 978                 return implied_condition_true(expr->unop);
 979
 980         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_DECREMENT)
 981                 return implied_not_equal(expr->unop, 1);
 982         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_INCREMENT)
 983                 return implied_not_equal(expr->unop, -1);
 984
 985         expr = strip_expr(expr);
 986         switch (expr->type) {
 987         case EXPR_COMPARE:
 988                 if (do_comparison(expr) == 1)
 989                         return 1;
 990                 break;
 991         case EXPR_PREOP:
 992                 if (expr->op == '!') {
 993                         if (implied_condition_false(expr->unop))
 994                                 return 1;
 995                         break;
 996                 }
 997                 break;
 998         default:
 999                 if (implied_not_equal(expr, 0) == 1)
1000                         return 1;
1001                 break;
1002         }
1003         return 0;
1004 }
1005
1006 int implied_condition_false(struct expression *expr)
1007 {
1008         struct expression *tmp;
1009         sval_t sval;
1010
1011         if (!expr)
1012                 return 0;
1013
1014         if (known_condition_false(expr))
1015                 return 1;
1016
1017         switch (expr->type) {
1018         case EXPR_COMPARE:
1019                 if (do_comparison(expr) == 2)
1020                         return 1;
1021         case EXPR_PREOP:
1022                 if (expr->op == '!') {
1023                         if (implied_condition_true(expr->unop))
1024                                 return 1;
1025                         break;
1026                 }
1027                 tmp = strip_expr(expr);
1028                 if (tmp != expr)
1029                         return implied_condition_false(tmp);
1030                 break;
1031         default:
1032                 if (get_implied_value(expr, &sval) && sval.value == 0)
1033                         return 1;
1034                 break;
1035         }
1036         return 0;
1037 }