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), 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         struct symbol *type;
 379
 380         type = get_type(expr);
 381
 382         get_implied_rl(expr->left, &left_ranges);
 383         get_implied_rl(expr->right, &right_ranges);
 384         left_ranges = cast_rl(type, left_ranges);
 385         right_ranges = cast_rl(type, right_ranges);
 386
 387         poss_true = possibly_true_rl(left_ranges, expr->op, right_ranges);
 388         poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
 389
 390         free_rl(&left_ranges);
 391         free_rl(&right_ranges);
 392
 393         if (!poss_true && !poss_false)
 394                 return 0;
 395         if (poss_true && !poss_false)
 396                 return 1;
 397         if (!poss_true && poss_false)
 398                 return 2;
 399         return 3;
 400 }
 401
 402 static sval_t handle_comparison(struct expression *expr, int *undefined, int implied)
 403 {
 404         sval_t left, right;
 405         int res;
 406
 407         if (get_value(expr->left, &left) && get_value(expr->right, &right)) {
 408                 struct data_range tmp_left, tmp_right;
 409
 410                 tmp_left.min = left;
 411                 tmp_left.max = left;
 412                 tmp_right.min = right;
 413                 tmp_right.max = right;
 414                 if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
 415                         return one;
 416                 return zero;
 417         }
 418
 419         if (implied == NOTIMPLIED) {
 420                 *undefined = 1;
 421                 return bogus;
 422         }
 423
 424         res = do_comparison(expr);
 425         if (res == 1)
 426                 return one;
 427         if (res == 2)
 428                 return zero;
 429
 430         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN)
 431                 return zero;
 432         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX)
 433                 return one;
 434
 435         *undefined = 1;
 436         return bogus;
 437 }
 438
 439 static sval_t handle_logical(struct expression *expr, int *undefined, int implied)
 440 {
 441         sval_t left, right;
 442         int left_known = 0;
 443         int right_known = 0;
 444
 445         if (implied == NOTIMPLIED) {
 446                 if (get_value(expr->left, &left))
 447                         left_known = 1;
 448                 if (get_value(expr->right, &right))
 449                         right_known = 1;
 450         } else {
 451                 if (get_implied_value(expr->left, &left))
 452                         left_known = 1;
 453                 if (get_implied_value(expr->right, &right))
 454                         right_known = 1;
 455         }
 456
 457         switch (expr->op) {
 458         case SPECIAL_LOGICAL_OR:
 459                 if (left_known && left.value)
 460                         return one;
 461                 if (right_known && right.value)
 462                         return one;
 463                 if (left_known && right_known)
 464                         return zero;
 465                 break;
 466         case SPECIAL_LOGICAL_AND:
 467                 if (left_known && right_known) {
 468                         if (left.value && right.value)
 469                                 return one;
 470                         return zero;
 471                 }
 472                 break;
 473         default:
 474                 *undefined = 1;
 475                 return bogus;
 476         }
 477
 478         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN)
 479                 return zero;
 480         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX)
 481                 return one;
 482
 483         *undefined = 1;
 484         return bogus;
 485 }
 486
 487 static sval_t handle_conditional(struct expression *expr, int *undefined, int implied)
 488 {
 489         if (known_condition_true(expr->conditional))
 490                 return _get_value(expr->cond_true, undefined, implied);
 491         if (known_condition_false(expr->conditional))
 492                 return _get_value(expr->cond_false, undefined, implied);
 493
 494         if (implied == NOTIMPLIED) {
 495                 *undefined = 1;
 496                 return bogus;
 497         }
 498
 499         if (implied_condition_true(expr->conditional))
 500                 return _get_value(expr->cond_true, undefined, implied);
 501         if (implied_condition_false(expr->conditional))
 502                 return _get_value(expr->cond_false, undefined, implied);
 503
 504         *undefined = 1;
 505         return bogus;
 506 }
 507
 508 static int get_local_value(struct expression *expr, sval_t *sval, int implied)
 509 {
 510         switch (implied) {
 511         case NOTIMPLIED:
 512         case IMPLIED:
 513                 return 0;
 514         case IMPLIED_MIN:
 515         case FUZZY_MIN:
 516         case ABSOLUTE_MIN:
 517                 return get_local_min_helper(expr, sval);
 518         case ABSOLUTE_MAX:
 519         case HARD_MAX:
 520         case IMPLIED_MAX:
 521         case FUZZY_MAX:
 522                 return get_local_max_helper(expr, sval);
 523         }
 524         return 0;
 525 }
 526
 527 static int get_implied_value_helper(struct expression *expr, sval_t *sval, int implied)
 528 {
 529         struct smatch_state *state;
 530         struct symbol *sym;
 531         char *name;
 532
 533         /* fixme: this should return the casted value */
 534
 535         expr = strip_expr(expr);
 536
 537         if (get_value(expr, sval))
 538                 return 1;
 539
 540         name = expr_to_var_sym(expr, &sym);
 541         if (!name)
 542                 return 0;
 543         *sval = sval_blank(expr);
 544         state = get_state(SMATCH_EXTRA, name, sym);
 545         free_string(name);
 546         if (!state || !state->data)
 547                 return get_local_value(expr, sval, implied);
 548         if (implied == IMPLIED) {
 549                 if (estate_get_single_value(state, sval))
 550                         return 1;
 551                 return 0;
 552         }
 553         if (implied == HARD_MAX) {
 554                 if (estate_get_hard_max(state, sval))
 555                         return 1;
 556                 return 0;
 557         }
 558         if (implied == IMPLIED_MAX || implied == ABSOLUTE_MAX) {
 559                 *sval = estate_max(state);
 560                 return 1;
 561         }
 562         *sval = estate_min(state);
 563         return 1;
 564 }
 565
 566 static int get_fuzzy_max_helper(struct expression *expr, sval_t *max)
 567 {
 568         struct sm_state *sm;
 569         struct sm_state *tmp;
 570         sval_t sval;
 571
 572         if (get_hard_max(expr, &sval)) {
 573                 *max = sval;
 574                 return 1;
 575         }
 576
 577         sm = get_sm_state_expr(SMATCH_EXTRA, expr);
 578         if (!sm)
 579                 return 0;
 580
 581         sval = sval_type_min(estate_type(sm->state));
 582         FOR_EACH_PTR(sm->possible, tmp) {
 583                 sval_t new_min;
 584
 585                 new_min = estate_min(tmp->state);
 586                 if (sval_cmp(new_min, sval) > 0)
 587                         sval = new_min;
 588         } END_FOR_EACH_PTR(tmp);
 589
 590         if (sval_is_min(sval))
 591                 return 0;
 592         if (sval.value == sval_type_min(sval.type).value + 1)  /* it's common to be on off */
 593                 return 0;
 594
 595         *max = sval_cast(get_type(expr), sval);
 596         return 1;
 597 }
 598
 599 static int get_fuzzy_min_helper(struct expression *expr, sval_t *min)
 600 {
 601         struct sm_state *sm;
 602         struct sm_state *tmp;
 603         sval_t sval;
 604
 605         sm = get_sm_state_expr(SMATCH_EXTRA, expr);
 606         if (!sm)
 607                 return 0;
 608
 609         if (!sval_is_min(estate_min(sm->state))) {
 610                 *min = estate_min(sm->state);
 611                 return 1;
 612         }
 613
 614         sval = sval_type_max(estate_type(sm->state));
 615         FOR_EACH_PTR(sm->possible, tmp) {
 616                 sval_t new_max;
 617
 618                 new_max = estate_max(tmp->state);
 619                 if (sval_cmp(new_max, sval) < 0)
 620                         sval = new_max;
 621         } END_FOR_EACH_PTR(tmp);
 622
 623         if (sval_is_max(sval))
 624                 return 0;
 625         *min = sval_cast(get_type(expr), sval);
 626         return 1;
 627 }
 628
 629 static sval_t _get_implied_value(struct expression *expr, int *undefined, int implied)
 630 {
 631         sval_t ret;
 632
 633         ret = sval_blank(expr);
 634
 635         switch (implied) {
 636         case IMPLIED:
 637         case IMPLIED_MAX:
 638         case IMPLIED_MIN:
 639         case HARD_MAX:
 640         case ABSOLUTE_MIN:
 641         case ABSOLUTE_MAX:
 642                 if (!get_implied_value_helper(expr, &ret, implied))
 643                         *undefined = 1;
 644                 break;
 645         case FUZZY_MAX:
 646                 if (!get_fuzzy_max_helper(expr, &ret))
 647                         *undefined = 1;
 648                 break;
 649         case FUZZY_MIN:
 650                 if (!get_fuzzy_min_helper(expr, &ret))
 651                         *undefined = 1;
 652                 break;
 653         default:
 654                 *undefined = 1;
 655         }
 656         return ret;
 657 }
 658
 659 static int get_const_value(struct expression *expr, sval_t *sval)
 660 {
 661         struct symbol *sym;
 662         sval_t right;
 663
 664         if (expr->type != EXPR_SYMBOL || !expr->symbol)
 665                 return 0;
 666         sym = expr->symbol;
 667         if (!(sym->ctype.modifiers & MOD_CONST))
 668                 return 0;
 669         if (get_value(sym->initializer, &right)) {
 670                 *sval = sval_cast(get_type(expr), right);
 671                 return 1;
 672         }
 673         return 0;
 674 }
 675
 676 static sval_t handle_sizeof(struct expression *expr)
 677 {
 678         struct symbol *sym;
 679         sval_t ret;
 680
 681         ret = sval_blank(expr);
 682         sym = expr->cast_type;
 683         if (!sym) {
 684                 sym = evaluate_expression(expr->cast_expression);
 685                 /*
 686                  * Expressions of restricted types will possibly get
 687                  * promoted - check that here
 688                  */
 689                 if (is_restricted_type(sym)) {
 690                         if (sym->bit_size < bits_in_int)
 691                                 sym = &int_ctype;
 692                 } else if (is_fouled_type(sym)) {
 693                         sym = &int_ctype;
 694                 }
 695         }
 696         examine_symbol_type(sym);
 697
 698         ret.type = size_t_ctype;
 699         if (sym->bit_size <= 0) /* sizeof(void) */
 700                 ret.value = 1;
 701         else
 702                 ret.value = bits_to_bytes(sym->bit_size);
 703
 704         return ret;
 705 }
 706
 707 static sval_t _get_value(struct expression *expr, int *undefined, int implied)
 708 {
 709         sval_t ret;
 710
 711         if (!expr) {
 712                 *undefined = 1;
 713                 return bogus;
 714         }
 715         if (*undefined)
 716                 return bogus;
 717
 718         expr = strip_parens(expr);
 719
 720         switch (expr->type) {
 721         case EXPR_VALUE:
 722                 ret = sval_from_val(expr, expr->value);
 723                 break;
 724         case EXPR_PREOP:
 725                 ret = handle_preop(expr, undefined, implied);
 726                 break;
 727         case EXPR_POSTOP:
 728                 ret = _get_value(expr->unop, undefined, implied);
 729                 break;
 730         case EXPR_CAST:
 731         case EXPR_FORCE_CAST:
 732         case EXPR_IMPLIED_CAST:
 733                 ret = _get_value(expr->cast_expression, undefined, implied);
 734                 ret = sval_cast(get_type(expr), ret);
 735                 break;
 736         case EXPR_BINOP:
 737                 ret = handle_binop(expr, undefined, implied);
 738                 break;
 739         case EXPR_COMPARE:
 740                 ret = handle_comparison(expr, undefined, implied);
 741                 break;
 742         case EXPR_LOGICAL:
 743                 ret = handle_logical(expr, undefined, implied);
 744                 break;
 745         case EXPR_PTRSIZEOF:
 746         case EXPR_SIZEOF:
 747                 ret = handle_sizeof(expr);
 748                 break;
 749         case EXPR_SYMBOL:
 750                 if (get_const_value(expr, &ret)) {
 751                         break;
 752                 }
 753                 ret = _get_implied_value(expr, undefined, implied);
 754                 break;
 755         case EXPR_SELECT:
 756         case EXPR_CONDITIONAL:
 757                 ret = handle_conditional(expr, undefined, implied);
 758                 break;
 759         default:
 760                 ret = _get_implied_value(expr, undefined, implied);
 761         }
 762         if (*undefined)
 763                 return bogus;
 764         return ret;
 765 }
 766
 767 /* returns 1 if it can get a value literal or else returns 0 */
 768 int get_value(struct expression *expr, sval_t *sval)
 769 {
 770         int undefined = 0;
 771         sval_t ret;
 772
 773         ret = _get_value(expr, &undefined, NOTIMPLIED);
 774         if (undefined)
 775                 return 0;
 776         *sval = ret;
 777         return 1;
 778 }
 779
 780 int get_implied_value(struct expression *expr, sval_t *sval)
 781 {
 782         int undefined = 0;
 783         sval_t ret;
 784
 785         ret =  _get_value(expr, &undefined, IMPLIED);
 786         if (undefined)
 787                 return 0;
 788         *sval = ret;
 789         return 1;
 790 }
 791
 792 int get_implied_min(struct expression *expr, sval_t *sval)
 793 {
 794         int undefined = 0;
 795         sval_t ret;
 796
 797         ret =  _get_value(expr, &undefined, IMPLIED_MIN);
 798         if (undefined)
 799                 return 0;
 800         *sval = ret;
 801         return 1;
 802 }
 803
 804 int get_implied_max(struct expression *expr, sval_t *sval)
 805 {
 806         int undefined = 0;
 807         sval_t ret;
 808
 809         ret =  _get_value(expr, &undefined, IMPLIED_MAX);
 810         if (undefined)
 811                 return 0;
 812         *sval = ret;
 813         return 1;
 814 }
 815
 816 int get_implied_rl(struct expression *expr, struct range_list **rl)
 817 {
 818         sval_t sval;
 819         struct smatch_state *state;
 820         sval_t min, max;
 821         int min_known = 0;
 822         int max_known = 0;
 823
 824         *rl = NULL;
 825
 826         expr = strip_parens(expr);
 827         if (!expr)
 828                 return 0;
 829
 830         state = get_state_expr(SMATCH_EXTRA, expr);
 831         if (state) {
 832                 *rl = clone_rl(estate_rl(state));
 833                 return 1;
 834         }
 835
 836         if (expr->type == EXPR_CALL) {
 837                 if (get_implied_return(expr, rl))
 838                         return 1;
 839                 *rl = db_return_vals(expr);
 840                 if (*rl)
 841                         return 1;
 842                 return 0;
 843         }
 844
 845         if (get_implied_value(expr, &sval)) {
 846                 add_range(rl, sval, sval);
 847                 return 1;
 848         }
 849
 850         if (get_local_rl(expr, rl))
 851                 return 1;
 852
 853         min_known = get_implied_min(expr, &min);
 854         max_known = get_implied_max(expr, &max);
 855         if (!min_known && !max_known)
 856                 return 0;
 857         if (!min_known)
 858                 get_absolute_min(expr, &min);
 859         if (!max_known)
 860                 get_absolute_max(expr, &max);
 861
 862         *rl = alloc_rl(min, max);
 863         return 1;
 864 }
 865
 866 int get_hard_max(struct expression *expr, sval_t *sval)
 867 {
 868         int undefined = 0;
 869         sval_t ret;
 870
 871         ret =  _get_value(expr, &undefined, HARD_MAX);
 872         if (undefined)
 873                 return 0;
 874         *sval = ret;
 875         return 1;
 876 }
 877
 878 int get_fuzzy_min(struct expression *expr, sval_t *sval)
 879 {
 880         int undefined = 0;
 881         sval_t ret;
 882
 883         ret =  _get_value(expr, &undefined, FUZZY_MIN);
 884         if (undefined)
 885                 return 0;
 886         *sval = ret;
 887         return 1;
 888 }
 889
 890 int get_fuzzy_max(struct expression *expr, sval_t *sval)
 891 {
 892         int undefined = 0;
 893         sval_t ret;
 894
 895         ret =  _get_value(expr, &undefined, FUZZY_MAX);
 896         if (undefined)
 897                 return 0;
 898         if (ret.uvalue > INT_MAX - 10000)
 899                 return 0;
 900         *sval = ret;
 901         return 1;
 902 }
 903
 904 int get_absolute_min(struct expression *expr, sval_t *sval)
 905 {
 906         int undefined = 0;
 907         struct symbol *type;
 908
 909         type = get_type(expr);
 910         if (!type)
 911                 type = &llong_ctype;  // FIXME: this is wrong but places assume get type can't fail.
 912         *sval =  _get_value(expr, &undefined, ABSOLUTE_MIN);
 913         if (undefined) {
 914                 *sval = sval_type_min(type);
 915                 return 1;
 916         }
 917
 918         if (sval_cmp(*sval, sval_type_min(type)) < 0)
 919                 *sval = sval_type_min(type);
 920         return 1;
 921 }
 922
 923 int get_absolute_max(struct expression *expr, sval_t *sval)
 924 {
 925         int undefined = 0;
 926         struct symbol *type;
 927
 928         type = get_type(expr);
 929         if (!type)
 930                 type = &llong_ctype;
 931         *sval = _get_value(expr, &undefined, ABSOLUTE_MAX);
 932         if (undefined) {
 933                 *sval = sval_type_max(type);
 934                 return 1;
 935         }
 936
 937         if (sval_cmp(sval_type_max(type), *sval) < 0)
 938                 *sval = sval_type_max(type);
 939         return 1;
 940 }
 941
 942 int known_condition_true(struct expression *expr)
 943 {
 944         sval_t tmp;
 945
 946         if (!expr)
 947                 return 0;
 948
 949         if (get_value(expr, &tmp) && tmp.value)
 950                 return 1;
 951
 952         return 0;
 953 }
 954
 955 int known_condition_false(struct expression *expr)
 956 {
 957         if (!expr)
 958                 return 0;
 959
 960         if (is_zero(expr))
 961                 return 1;
 962
 963         if (expr->type == EXPR_CALL) {
 964                 if (sym_name_is("__builtin_constant_p", expr->fn))
 965                         return 1;
 966         }
 967         return 0;
 968 }
 969
 970 int implied_condition_true(struct expression *expr)
 971 {
 972         sval_t tmp;
 973
 974         if (!expr)
 975                 return 0;
 976
 977         if (known_condition_true(expr))
 978                 return 1;
 979         if (get_implied_value(expr, &tmp) && tmp.value)
 980                 return 1;
 981
 982         if (expr->type == EXPR_POSTOP)
 983                 return implied_condition_true(expr->unop);
 984
 985         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_DECREMENT)
 986                 return implied_not_equal(expr->unop, 1);
 987         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_INCREMENT)
 988                 return implied_not_equal(expr->unop, -1);
 989
 990         expr = strip_expr(expr);
 991         switch (expr->type) {
 992         case EXPR_COMPARE:
 993                 if (do_comparison(expr) == 1)
 994                         return 1;
 995                 break;
 996         case EXPR_PREOP:
 997                 if (expr->op == '!') {
 998                         if (implied_condition_false(expr->unop))
 999                                 return 1;
1000                         break;
1001                 }
1002                 break;
1003         default:
1004                 if (implied_not_equal(expr, 0) == 1)
1005                         return 1;
1006                 break;
1007         }
1008         return 0;
1009 }
1010
1011 int implied_condition_false(struct expression *expr)
1012 {
1013         struct expression *tmp;
1014         sval_t sval;
1015
1016         if (!expr)
1017                 return 0;
1018
1019         if (known_condition_false(expr))
1020                 return 1;
1021
1022         switch (expr->type) {
1023         case EXPR_COMPARE:
1024                 if (do_comparison(expr) == 2)
1025                         return 1;
1026         case EXPR_PREOP:
1027                 if (expr->op == '!') {
1028                         if (implied_condition_true(expr->unop))
1029                                 return 1;
1030                         break;
1031                 }
1032                 tmp = strip_expr(expr);
1033                 if (tmp != expr)
1034                         return implied_condition_false(tmp);
1035                 break;
1036         default:
1037                 if (get_implied_value(expr, &sval) && sval.value == 0)
1038                         return 1;
1039                 break;
1040         }
1041         return 0;
1042 }