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         left = _get_value(expr->left, undefined, implied);
 262         if (!*undefined)
 263                 return sval_binop(left, '%', right);
 264
 265         switch (implied) {
 266         case NOTIMPLIED:
 267         case IMPLIED:
 268                 return bogus;
 269         case IMPLIED_MIN:
 270         case FUZZY_MIN:
 271         case ABSOLUTE_MIN:
 272                 *undefined = 0;
 273                 return sval_type_val(get_type(expr->left), 0);
 274         case IMPLIED_MAX:
 275         case FUZZY_MAX:
 276         case ABSOLUTE_MAX:
 277                 *undefined = 0;
 278                 right = sval_cast(get_type(expr), right);
 279                 right.value--;
 280                 return right;
 281         }
 282         return bogus;
 283 }
 284
 285 static sval_t handle_binop(struct expression *expr, int *undefined, int implied)
 286 {
 287         struct symbol *type;
 288         sval_t left, right;
 289         sval_t ret = {.type = &int_ctype, {.value = 123456} };
 290         int local_undef = 0;
 291
 292         switch (expr->op) {
 293         case '%':
 294                 return handle_mod(expr, undefined, implied);
 295         case '&':
 296                 left = _get_value(expr->left, &local_undef, implied);
 297                 if (local_undef) {
 298                         if (implied == IMPLIED_MIN || implied == ABSOLUTE_MIN) {
 299                                 ret = sval_blank(expr->left);
 300                                 ret.value = 0;
 301                                 return ret;
 302                         }
 303                         if (implied != IMPLIED_MAX && implied != ABSOLUTE_MAX)
 304                                 *undefined = 1;
 305                         if (!get_absolute_max(expr->left, &left))
 306                                 *undefined = 1;
 307                 }
 308                 right = _get_value(expr->right, undefined, implied);
 309                 if (*undefined)
 310                         return bogus;
 311                 return sval_binop(left, '&', right);
 312
 313         case SPECIAL_RIGHTSHIFT:
 314                 left = _get_value(expr->left, &local_undef, implied);
 315                 if (local_undef) {
 316                         if (implied == IMPLIED_MIN || implied == ABSOLUTE_MIN) {
 317                                 ret = sval_blank(expr->left);
 318                                 ret.value = 0;
 319                                 return ret;
 320                         }
 321                         if (implied != IMPLIED_MAX && implied != ABSOLUTE_MAX)
 322                                 *undefined = 1;
 323                         if (!get_absolute_max(expr->left, &left))
 324                                 *undefined = 1;
 325                 }
 326                 right = _get_value(expr->right, undefined, implied);
 327                 if (*undefined)
 328                         return bogus;
 329                 return sval_binop(left, SPECIAL_RIGHTSHIFT, right);
 330         case '-':
 331                 return handle_subtract(expr, undefined, implied);
 332         }
 333
 334         left = _get_value(expr->left, undefined, implied);
 335         right = _get_value(expr->right, undefined, implied);
 336
 337         if (*undefined)
 338                 return bogus;
 339
 340         type = get_type(expr);
 341         left = sval_cast(type, left);
 342         right = sval_cast(type, right);
 343
 344         switch (implied) {
 345         case IMPLIED_MAX:
 346         case ABSOLUTE_MAX:
 347                 if (sval_binop_overflows(left, expr->op, right))
 348                         return sval_type_max(get_type(expr));
 349                 break;
 350         case HARD_MAX:
 351         case FUZZY_MAX:
 352                 if (sval_binop_overflows(left, expr->op, right)) {
 353                         *undefined = 1;
 354                         return bogus;
 355                 }
 356         }
 357
 358         switch (expr->op) {
 359         case '/':
 360                 return handle_divide(expr, undefined, implied);
 361         case '%':
 362                 if (right.value == 0) {
 363                         *undefined = 1;
 364                         return bogus;
 365                 } else {
 366                         return sval_binop(left, '%', right);
 367                 }
 368         default:
 369                 ret = sval_binop(left, expr->op, right);
 370         }
 371         return ret;
 372 }
 373
 374 static int do_comparison(struct expression *expr)
 375 {
 376         struct range_list *left_ranges = NULL;
 377         struct range_list *right_ranges = NULL;
 378         int poss_true, poss_false;
 379
 380         get_implied_rl(expr->left, &left_ranges);
 381         get_implied_rl(expr->right, &right_ranges);
 382
 383         poss_true = possibly_true_rl(left_ranges, expr->op, right_ranges);
 384         poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
 385
 386         free_rl(&left_ranges);
 387         free_rl(&right_ranges);
 388
 389         if (!poss_true && !poss_false)
 390                 return 0;
 391         if (poss_true && !poss_false)
 392                 return 1;
 393         if (!poss_true && poss_false)
 394                 return 2;
 395         return 3;
 396 }
 397
 398 static sval_t handle_comparison(struct expression *expr, int *undefined, int implied)
 399 {
 400         sval_t left, right;
 401         int res;
 402
 403         if (get_value(expr->left, &left) && get_value(expr->right, &right)) {
 404                 struct data_range tmp_left, tmp_right;
 405
 406                 tmp_left.min = left;
 407                 tmp_left.max = left;
 408                 tmp_right.min = right;
 409                 tmp_right.max = right;
 410                 if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
 411                         return one;
 412                 return zero;
 413         }
 414
 415         if (implied == NOTIMPLIED) {
 416                 *undefined = 1;
 417                 return bogus;
 418         }
 419
 420         res = do_comparison(expr);
 421         if (res == 1)
 422                 return one;
 423         if (res == 2)
 424                 return zero;
 425
 426         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN)
 427                 return zero;
 428         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX)
 429                 return one;
 430
 431         *undefined = 1;
 432         return bogus;
 433 }
 434
 435 static sval_t handle_logical(struct expression *expr, int *undefined, int implied)
 436 {
 437         sval_t left, right;
 438         int left_known = 0;
 439         int right_known = 0;
 440
 441         if (implied == NOTIMPLIED) {
 442                 if (get_value(expr->left, &left))
 443                         left_known = 1;
 444                 if (get_value(expr->right, &right))
 445                         right_known = 1;
 446         } else {
 447                 if (get_implied_value(expr->left, &left))
 448                         left_known = 1;
 449                 if (get_implied_value(expr->right, &right))
 450                         right_known = 1;
 451         }
 452
 453         switch (expr->op) {
 454         case SPECIAL_LOGICAL_OR:
 455                 if (left_known && left.value)
 456                         return one;
 457                 if (right_known && right.value)
 458                         return one;
 459                 if (left_known && right_known)
 460                         return zero;
 461                 break;
 462         case SPECIAL_LOGICAL_AND:
 463                 if (left_known && right_known) {
 464                         if (left.value && right.value)
 465                                 return one;
 466                         return zero;
 467                 }
 468                 break;
 469         default:
 470                 *undefined = 1;
 471                 return bogus;
 472         }
 473
 474         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN)
 475                 return zero;
 476         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX)
 477                 return one;
 478
 479         *undefined = 1;
 480         return bogus;
 481 }
 482
 483 static sval_t handle_conditional(struct expression *expr, int *undefined, int implied)
 484 {
 485         if (known_condition_true(expr->conditional))
 486                 return _get_value(expr->cond_true, undefined, implied);
 487         if (known_condition_false(expr->conditional))
 488                 return _get_value(expr->cond_false, undefined, implied);
 489
 490         if (implied == NOTIMPLIED) {
 491                 *undefined = 1;
 492                 return bogus;
 493         }
 494
 495         if (implied_condition_true(expr->conditional))
 496                 return _get_value(expr->cond_true, undefined, implied);
 497         if (implied_condition_false(expr->conditional))
 498                 return _get_value(expr->cond_false, undefined, implied);
 499
 500         *undefined = 1;
 501         return bogus;
 502 }
 503
 504 static int get_implied_value_helper(struct expression *expr, sval_t *sval, int implied)
 505 {
 506         struct smatch_state *state;
 507         struct symbol *sym;
 508         char *name;
 509
 510         /* fixme: this should return the casted value */
 511
 512         expr = strip_expr(expr);
 513
 514         if (get_value(expr, sval))
 515                 return 1;
 516
 517         name = expr_to_var_sym(expr, &sym);
 518         if (!name)
 519                 return 0;
 520         *sval = sval_blank(expr);
 521         state = get_state(SMATCH_EXTRA, name, sym);
 522         free_string(name);
 523         if (!state || !state->data)
 524                 return 0;
 525         if (implied == IMPLIED) {
 526                 if (estate_get_single_value(state, sval))
 527                         return 1;
 528                 return 0;
 529         }
 530         if (implied == HARD_MAX) {
 531                 if (estate_get_hard_max(state, sval))
 532                         return 1;
 533                 return 0;
 534         }
 535         if (implied == IMPLIED_MAX || implied == ABSOLUTE_MAX) {
 536                 *sval = estate_max(state);
 537                 return 1;
 538         }
 539         *sval = estate_min(state);
 540         return 1;
 541 }
 542
 543 static int get_fuzzy_max_helper(struct expression *expr, sval_t *max)
 544 {
 545         struct sm_state *sm;
 546         struct sm_state *tmp;
 547         sval_t sval;
 548
 549         if (get_hard_max(expr, &sval)) {
 550                 *max = sval;
 551                 return 1;
 552         }
 553
 554         sm = get_sm_state_expr(SMATCH_EXTRA, expr);
 555         if (!sm)
 556                 return 0;
 557
 558         sval = sval_type_min(estate_type(sm->state));
 559         FOR_EACH_PTR(sm->possible, tmp) {
 560                 sval_t new_min;
 561
 562                 new_min = estate_min(tmp->state);
 563                 if (sval_cmp(new_min, sval) > 0)
 564                         sval = new_min;
 565         } END_FOR_EACH_PTR(tmp);
 566
 567         if (sval_is_min(sval))
 568                 return 0;
 569         if (sval.value == sval_type_min(sval.type).value + 1)  /* it's common to be on off */
 570                 return 0;
 571
 572         *max = sval_cast(get_type(expr), sval);
 573         return 1;
 574 }
 575
 576 static int get_fuzzy_min_helper(struct expression *expr, sval_t *min)
 577 {
 578         struct sm_state *sm;
 579         struct sm_state *tmp;
 580         sval_t sval;
 581
 582         sm = get_sm_state_expr(SMATCH_EXTRA, expr);
 583         if (!sm)
 584                 return 0;
 585
 586         if (!sval_is_min(estate_min(sm->state))) {
 587                 *min = estate_min(sm->state);
 588                 return 1;
 589         }
 590
 591         sval = sval_type_max(estate_type(sm->state));
 592         FOR_EACH_PTR(sm->possible, tmp) {
 593                 sval_t new_max;
 594
 595                 new_max = estate_max(tmp->state);
 596                 if (sval_cmp(new_max, sval) < 0)
 597                         sval = new_max;
 598         } END_FOR_EACH_PTR(tmp);
 599
 600         if (sval_is_max(sval))
 601                 return 0;
 602         *min = sval_cast(get_type(expr), sval);
 603         return 1;
 604 }
 605
 606 static sval_t _get_implied_value(struct expression *expr, int *undefined, int implied)
 607 {
 608         sval_t ret;
 609
 610         ret = sval_blank(expr);
 611
 612         switch (implied) {
 613         case IMPLIED:
 614         case IMPLIED_MAX:
 615         case IMPLIED_MIN:
 616         case HARD_MAX:
 617         case ABSOLUTE_MIN:
 618         case ABSOLUTE_MAX:
 619                 if (!get_implied_value_helper(expr, &ret, implied))
 620                         *undefined = 1;
 621                 break;
 622         case FUZZY_MAX:
 623                 if (!get_fuzzy_max_helper(expr, &ret))
 624                         *undefined = 1;
 625                 break;
 626         case FUZZY_MIN:
 627                 if (!get_fuzzy_min_helper(expr, &ret))
 628                         *undefined = 1;
 629                 break;
 630         default:
 631                 *undefined = 1;
 632         }
 633         return ret;
 634 }
 635
 636 static int get_const_value(struct expression *expr, sval_t *sval)
 637 {
 638         struct symbol *sym;
 639         sval_t right;
 640
 641         if (expr->type != EXPR_SYMBOL || !expr->symbol)
 642                 return 0;
 643         sym = expr->symbol;
 644         if (!(sym->ctype.modifiers & MOD_CONST))
 645                 return 0;
 646         if (get_value(sym->initializer, &right)) {
 647                 *sval = sval_cast(get_type(expr), right);
 648                 return 1;
 649         }
 650         return 0;
 651 }
 652
 653 static sval_t handle_sizeof(struct expression *expr)
 654 {
 655         struct symbol *sym;
 656         sval_t ret;
 657
 658         ret = sval_blank(expr);
 659         sym = expr->cast_type;
 660         if (!sym) {
 661                 sym = evaluate_expression(expr->cast_expression);
 662                 /*
 663                  * Expressions of restricted types will possibly get
 664                  * promoted - check that here
 665                  */
 666                 if (is_restricted_type(sym)) {
 667                         if (sym->bit_size < bits_in_int)
 668                                 sym = &int_ctype;
 669                 } else if (is_fouled_type(sym)) {
 670                         sym = &int_ctype;
 671                 }
 672         }
 673         examine_symbol_type(sym);
 674
 675         ret.type = size_t_ctype;
 676         if (sym->bit_size <= 0) /* sizeof(void) */
 677                 ret.value = 1;
 678         else
 679                 ret.value = bits_to_bytes(sym->bit_size);
 680
 681         return ret;
 682 }
 683
 684 static sval_t _get_value(struct expression *expr, int *undefined, int implied)
 685 {
 686         sval_t ret;
 687
 688         if (!expr) {
 689                 *undefined = 1;
 690                 return bogus;
 691         }
 692         if (*undefined)
 693                 return bogus;
 694
 695         expr = strip_parens(expr);
 696
 697         switch (expr->type) {
 698         case EXPR_VALUE:
 699                 ret = sval_from_val(expr, expr->value);
 700                 break;
 701         case EXPR_PREOP:
 702                 ret = handle_preop(expr, undefined, implied);
 703                 break;
 704         case EXPR_POSTOP:
 705                 ret = _get_value(expr->unop, undefined, implied);
 706                 break;
 707         case EXPR_CAST:
 708         case EXPR_FORCE_CAST:
 709         case EXPR_IMPLIED_CAST:
 710                 ret = _get_value(expr->cast_expression, undefined, implied);
 711                 ret = sval_cast(get_type(expr), ret);
 712                 break;
 713         case EXPR_BINOP:
 714                 ret = handle_binop(expr, undefined, implied);
 715                 break;
 716         case EXPR_COMPARE:
 717                 ret = handle_comparison(expr, undefined, implied);
 718                 break;
 719         case EXPR_LOGICAL:
 720                 ret = handle_logical(expr, undefined, implied);
 721                 break;
 722         case EXPR_PTRSIZEOF:
 723         case EXPR_SIZEOF:
 724                 ret = handle_sizeof(expr);
 725                 break;
 726         case EXPR_SYMBOL:
 727                 if (get_const_value(expr, &ret)) {
 728                         break;
 729                 }
 730                 ret = _get_implied_value(expr, undefined, implied);
 731                 break;
 732         case EXPR_SELECT:
 733         case EXPR_CONDITIONAL:
 734                 ret = handle_conditional(expr, undefined, implied);
 735                 break;
 736         default:
 737                 ret = _get_implied_value(expr, undefined, implied);
 738         }
 739         if (*undefined)
 740                 return bogus;
 741         return ret;
 742 }
 743
 744 /* returns 1 if it can get a value literal or else returns 0 */
 745 int get_value(struct expression *expr, sval_t *sval)
 746 {
 747         int undefined = 0;
 748         sval_t ret;
 749
 750         ret = _get_value(expr, &undefined, NOTIMPLIED);
 751         if (undefined)
 752                 return 0;
 753         *sval = ret;
 754         return 1;
 755 }
 756
 757 int get_implied_value(struct expression *expr, sval_t *sval)
 758 {
 759         int undefined = 0;
 760         sval_t ret;
 761
 762         ret =  _get_value(expr, &undefined, IMPLIED);
 763         if (undefined)
 764                 return 0;
 765         *sval = ret;
 766         return 1;
 767 }
 768
 769 int get_implied_min(struct expression *expr, sval_t *sval)
 770 {
 771         int undefined = 0;
 772         sval_t ret;
 773
 774         ret =  _get_value(expr, &undefined, IMPLIED_MIN);
 775         if (undefined)
 776                 return 0;
 777         *sval = ret;
 778         return 1;
 779 }
 780
 781 int get_implied_max(struct expression *expr, sval_t *sval)
 782 {
 783         int undefined = 0;
 784         sval_t ret;
 785
 786         ret =  _get_value(expr, &undefined, IMPLIED_MAX);
 787         if (undefined)
 788                 return 0;
 789         *sval = ret;
 790         return 1;
 791 }
 792
 793 int get_implied_rl(struct expression *expr, struct range_list **rl)
 794 {
 795         sval_t sval;
 796         struct smatch_state *state;
 797         sval_t min, max;
 798         int min_known = 0;
 799         int max_known = 0;
 800
 801         *rl = NULL;
 802
 803         expr = strip_parens(expr);
 804         if (!expr)
 805                 return 0;
 806
 807         state = get_state_expr(SMATCH_EXTRA, expr);
 808         if (state) {
 809                 *rl = clone_rl(estate_rl(state));
 810                 return 1;
 811         }
 812
 813         if (expr->type == EXPR_CALL) {
 814                 if (get_implied_return(expr, rl))
 815                         return 1;
 816                 *rl = db_return_vals(expr);
 817                 if (*rl)
 818                         return 1;
 819                 return 0;
 820         }
 821
 822         if (get_implied_value(expr, &sval)) {
 823                 add_range(rl, sval, sval);
 824                 return 1;
 825         }
 826
 827         min_known = get_implied_min(expr, &min);
 828         max_known = get_implied_max(expr, &max);
 829         if (!min_known && !max_known)
 830                 return 0;
 831         if (!min_known)
 832                 get_absolute_min(expr, &min);
 833         if (!max_known)
 834                 get_absolute_max(expr, &max);
 835
 836         *rl = alloc_rl(min, max);
 837         return 1;
 838 }
 839
 840 int get_hard_max(struct expression *expr, sval_t *sval)
 841 {
 842         int undefined = 0;
 843         sval_t ret;
 844
 845         ret =  _get_value(expr, &undefined, HARD_MAX);
 846         if (undefined)
 847                 return 0;
 848         *sval = ret;
 849         return 1;
 850 }
 851
 852 int get_fuzzy_min(struct expression *expr, sval_t *sval)
 853 {
 854         int undefined = 0;
 855         sval_t ret;
 856
 857         ret =  _get_value(expr, &undefined, FUZZY_MIN);
 858         if (undefined)
 859                 return 0;
 860         *sval = ret;
 861         return 1;
 862 }
 863
 864 int get_fuzzy_max(struct expression *expr, sval_t *sval)
 865 {
 866         int undefined = 0;
 867         sval_t ret;
 868
 869         ret =  _get_value(expr, &undefined, FUZZY_MAX);
 870         if (undefined)
 871                 return 0;
 872         if (ret.uvalue > INT_MAX - 10000)
 873                 return 0;
 874         *sval = ret;
 875         return 1;
 876 }
 877
 878 int get_absolute_min(struct expression *expr, sval_t *sval)
 879 {
 880         int undefined = 0;
 881         struct symbol *type;
 882
 883         type = get_type(expr);
 884         if (!type)
 885                 type = &llong_ctype;  // FIXME: this is wrong but places assume get type can't fail.
 886         *sval =  _get_value(expr, &undefined, ABSOLUTE_MIN);
 887         if (undefined) {
 888                 *sval = sval_type_min(type);
 889                 return 1;
 890         }
 891
 892         if (sval_cmp(*sval, sval_type_min(type)) < 0)
 893                 *sval = sval_type_min(type);
 894         return 1;
 895 }
 896
 897 int get_absolute_max(struct expression *expr, sval_t *sval)
 898 {
 899         int undefined = 0;
 900         struct symbol *type;
 901
 902         type = get_type(expr);
 903         if (!type)
 904                 type = &llong_ctype;
 905         *sval = _get_value(expr, &undefined, ABSOLUTE_MAX);
 906         if (undefined) {
 907                 *sval = sval_type_max(type);
 908                 return 1;
 909         }
 910
 911         if (sval_cmp(sval_type_max(type), *sval) < 0)
 912                 *sval = sval_type_max(type);
 913         return 1;
 914 }
 915
 916 int known_condition_true(struct expression *expr)
 917 {
 918         sval_t tmp;
 919
 920         if (!expr)
 921                 return 0;
 922
 923         if (get_value(expr, &tmp) && tmp.value)
 924                 return 1;
 925
 926         return 0;
 927 }
 928
 929 int known_condition_false(struct expression *expr)
 930 {
 931         if (!expr)
 932                 return 0;
 933
 934         if (is_zero(expr))
 935                 return 1;
 936
 937         if (expr->type == EXPR_CALL) {
 938                 if (sym_name_is("__builtin_constant_p", expr->fn))
 939                         return 1;
 940         }
 941         return 0;
 942 }
 943
 944 int implied_condition_true(struct expression *expr)
 945 {
 946         sval_t tmp;
 947
 948         if (!expr)
 949                 return 0;
 950
 951         if (known_condition_true(expr))
 952                 return 1;
 953         if (get_implied_value(expr, &tmp) && tmp.value)
 954                 return 1;
 955
 956         if (expr->type == EXPR_POSTOP)
 957                 return implied_condition_true(expr->unop);
 958
 959         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_DECREMENT)
 960                 return implied_not_equal(expr->unop, 1);
 961         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_INCREMENT)
 962                 return implied_not_equal(expr->unop, -1);
 963
 964         expr = strip_expr(expr);
 965         switch (expr->type) {
 966         case EXPR_COMPARE:
 967                 if (do_comparison(expr) == 1)
 968                         return 1;
 969                 break;
 970         case EXPR_PREOP:
 971                 if (expr->op == '!') {
 972                         if (implied_condition_false(expr->unop))
 973                                 return 1;
 974                         break;
 975                 }
 976                 break;
 977         default:
 978                 if (implied_not_equal(expr, 0) == 1)
 979                         return 1;
 980                 break;
 981         }
 982         return 0;
 983 }
 984
 985 int implied_condition_false(struct expression *expr)
 986 {
 987         struct expression *tmp;
 988         sval_t sval;
 989
 990         if (!expr)
 991                 return 0;
 992
 993         if (known_condition_false(expr))
 994                 return 1;
 995
 996         switch (expr->type) {
 997         case EXPR_COMPARE:
 998                 if (do_comparison(expr) == 2)
 999                         return 1;
1000         case EXPR_PREOP:
1001                 if (expr->op == '!') {
1002                         if (implied_condition_true(expr->unop))
1003                                 return 1;
1004                         break;
1005                 }
1006                 tmp = strip_expr(expr);
1007                 if (tmp != expr)
1008                         return implied_condition_false(tmp);
1009                 break;
1010         default:
1011                 if (get_implied_value(expr, &sval) && sval.value == 0)
1012                         return 1;
1013                 break;
1014         }
1015         return 0;
1016 }