smatch_math.c

   1 /*
   2  * Copyright (C) 2010 Dan Carpenter.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17
  18 #include "symbol.h"
  19 #include "smatch.h"
  20 #include "smatch_slist.h"
  21 #include "smatch_extra.h"
  22
  23 static struct range_list *_get_rl(struct expression *expr, int implied, int *recurse_cnt);
  24 static struct range_list *handle_variable(struct expression *expr, int implied, int *recurse_cnt);
  25 static struct range_list *(*custom_handle_variable)(struct expression *expr);
  26
  27 static int get_implied_value_internal(struct expression *expr, sval_t *sval, int *recurse_cnt);
  28 static int get_absolute_rl_internal(struct expression *expr, struct range_list **rl, int *recurse_cnt);
  29
  30 static sval_t zero  = {.type = &int_ctype, {.value = 0} };
  31 static sval_t one   = {.type = &int_ctype, {.value = 1} };
  32
  33 struct range_list *rl_zero(void)
  34 {
  35         return alloc_rl(zero, zero);
  36 }
  37
  38 struct range_list *rl_one(void)
  39 {
  40         return alloc_rl(one, one);
  41 }
  42
  43 enum {
  44         RL_EXACT,
  45         RL_HARD,
  46         RL_FUZZY,
  47         RL_IMPLIED,
  48         RL_ABSOLUTE,
  49         RL_REAL_ABSOLUTE,
  50 };
  51
  52 static struct range_list *last_stmt_rl(struct statement *stmt, int implied, int *recurse_cnt)
  53 {
  54         struct expression *expr;
  55
  56         if (!stmt)
  57                 return NULL;
  58
  59         stmt = last_ptr_list((struct ptr_list *)stmt->stmts);
  60         if (stmt->type == STMT_LABEL) {
  61                 if (stmt->label_statement &&
  62                     stmt->label_statement->type == STMT_EXPRESSION)
  63                         expr = stmt->label_statement->expression;
  64                 else
  65                         return NULL;
  66         } else if (stmt->type == STMT_EXPRESSION) {
  67                 expr = stmt->expression;
  68         } else {
  69                 return NULL;
  70         }
  71         return _get_rl(expr, implied, recurse_cnt);
  72 }
  73
  74 static struct range_list *handle_expression_statement_rl(struct expression *expr, int implied, int *recurse_cnt)
  75 {
  76         return last_stmt_rl(get_expression_statement(expr), implied, recurse_cnt);
  77 }
  78
  79 static struct range_list *handle_ampersand_rl(struct expression *expr, int implied, int *recurse_cnt)
  80 {
  81         struct range_list *rl;
  82
  83         if (implied == RL_EXACT || implied == RL_HARD)
  84                 return NULL;
  85         if (get_address_rl(expr, &rl))
  86                 return rl;
  87         return alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
  88 }
  89
  90 static struct range_list *handle_negate_rl(struct expression *expr, int implied, int *recurse_cnt)
  91 {
  92         if (known_condition_true(expr->unop))
  93                 return rl_zero();
  94         if (known_condition_false(expr->unop))
  95                 return rl_one();
  96
  97         if (implied == RL_EXACT)
  98                 return NULL;
  99
 100         if (implied_condition_true(expr->unop))
 101                 return rl_zero();
 102         if (implied_condition_false(expr->unop))
 103                 return rl_one();
 104         return alloc_rl(zero, one);
 105 }
 106
 107 static struct range_list *handle_bitwise_negate(struct expression *expr, int implied, int *recurse_cnt)
 108 {
 109         struct range_list *rl;
 110         sval_t sval;
 111
 112         rl = _get_rl(expr->unop, implied, recurse_cnt);
 113         if (!rl_to_sval(rl, &sval))
 114                 return NULL;
 115         sval = sval_preop(sval, '~');
 116         sval_cast(get_type(expr->unop), sval);
 117         return alloc_rl(sval, sval);
 118 }
 119
 120 static struct range_list *handle_minus_preop(struct expression *expr, int implied, int *recurse_cnt)
 121 {
 122         struct range_list *rl;
 123         sval_t sval;
 124
 125         rl = _get_rl(expr->unop, implied, recurse_cnt);
 126         if (!rl_to_sval(rl, &sval))
 127                 return NULL;
 128         sval = sval_preop(sval, '-');
 129         return alloc_rl(sval, sval);
 130 }
 131
 132 static struct range_list *handle_preop_rl(struct expression *expr, int implied, int *recurse_cnt)
 133 {
 134         switch (expr->op) {
 135         case '&':
 136                 return handle_ampersand_rl(expr, implied, recurse_cnt);
 137         case '!':
 138                 return handle_negate_rl(expr, implied, recurse_cnt);
 139         case '~':
 140                 return handle_bitwise_negate(expr, implied, recurse_cnt);
 141         case '-':
 142                 return handle_minus_preop(expr, implied, recurse_cnt);
 143         case '*':
 144                 return handle_variable(expr, implied, recurse_cnt);
 145         case '(':
 146                 return handle_expression_statement_rl(expr, implied, recurse_cnt);
 147         default:
 148                 return NULL;
 149         }
 150 }
 151
 152 static struct range_list *handle_divide_rl(struct expression *expr, int implied, int *recurse_cnt)
 153 {
 154         struct range_list *left_rl, *right_rl;
 155         struct symbol *type;
 156
 157         type = get_type(expr);
 158
 159         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 160         left_rl = cast_rl(type, left_rl);
 161         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 162         right_rl = cast_rl(type, right_rl);
 163
 164         if (!left_rl || !right_rl)
 165                 return NULL;
 166
 167         if (implied != RL_REAL_ABSOLUTE) {
 168                 if (is_whole_rl(left_rl) || is_whole_rl(right_rl))
 169                         return NULL;
 170         }
 171
 172         return rl_binop(left_rl, '/', right_rl);
 173 }
 174
 175 static struct range_list *handle_subtract_rl(struct expression *expr, int implied, int *recurse_cnt)
 176 {
 177         struct symbol *type;
 178         struct range_list *left_rl, *right_rl;
 179         sval_t max, min, tmp;
 180         int comparison;
 181
 182         type = get_type(expr);
 183         comparison = get_comparison(expr->left, expr->right);
 184
 185         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 186         left_rl = cast_rl(type, left_rl);
 187         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 188         right_rl = cast_rl(type, right_rl);
 189
 190         if ((!left_rl || !right_rl) &&
 191             (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY))
 192                 return NULL;
 193
 194         if (!left_rl)
 195                 left_rl = alloc_whole_rl(type);
 196         if (!right_rl)
 197                 right_rl = alloc_whole_rl(type);
 198
 199         /* negative values complicate everything fix this later */
 200         if (sval_is_negative(rl_min(right_rl)))
 201                 return NULL;
 202         max = rl_max(left_rl);
 203
 204         switch (comparison) {
 205         case '>':
 206         case SPECIAL_UNSIGNED_GT:
 207                 min = sval_type_val(type, 1);
 208                 max = rl_max(left_rl);
 209                 break;
 210         case SPECIAL_GTE:
 211         case SPECIAL_UNSIGNED_GTE:
 212                 min = sval_type_val(type, 0);
 213                 max = rl_max(left_rl);
 214                 break;
 215         default:
 216                 if (sval_binop_overflows(rl_min(left_rl), '-', rl_max(right_rl)))
 217                         return NULL;
 218                 min = sval_type_min(type);
 219         }
 220
 221         if (!sval_binop_overflows(rl_min(left_rl), '-', rl_max(right_rl))) {
 222                 tmp = sval_binop(rl_min(left_rl), '-', rl_max(right_rl));
 223                 if (sval_cmp(tmp, min) > 0)
 224                         min = tmp;
 225         }
 226
 227         if (!sval_is_max(rl_max(left_rl))) {
 228                 tmp = sval_binop(rl_max(left_rl), '-', rl_min(right_rl));
 229                 if (sval_cmp(tmp, max) < 0)
 230                         max = tmp;
 231         }
 232
 233         if (sval_is_min(min) && sval_is_max(max))
 234                 return NULL;
 235
 236         return cast_rl(type, alloc_rl(min, max));
 237 }
 238
 239 static struct range_list *handle_mod_rl(struct expression *expr, int implied, int *recurse_cnt)
 240 {
 241         struct range_list *rl;
 242         sval_t left, right, sval;
 243
 244         if (implied == RL_EXACT) {
 245                 if (!get_value(expr->right, &right))
 246                         return NULL;
 247                 if (!get_value(expr->left, &left))
 248                         return NULL;
 249                 sval = sval_binop(left, '%', right);
 250                 return alloc_rl(sval, sval);
 251         }
 252         /* if we can't figure out the right side it's probably hopeless */
 253         if (!get_implied_value_internal(expr->right, &right, recurse_cnt))
 254                 return NULL;
 255
 256         right = sval_cast(get_type(expr), right);
 257         right.value--;
 258
 259         rl = _get_rl(expr->left, implied, recurse_cnt);
 260         if (rl && rl_max(rl).uvalue < right.uvalue)
 261                 right.uvalue = rl_max(rl).uvalue;
 262
 263         return alloc_rl(zero, right);
 264 }
 265
 266 static sval_t sval_lowest_set_bit(sval_t sval)
 267 {
 268         int i;
 269         int found = 0;
 270
 271         for (i = 0; i < 64; i++) {
 272                 if (sval.uvalue & 1ULL << i) {
 273                         if (!found++)
 274                                 continue;
 275                         sval.uvalue &= ~(1ULL << i);
 276                 }
 277         }
 278         return sval;
 279 }
 280
 281 static struct range_list *handle_bitwise_AND(struct expression *expr, int implied, int *recurse_cnt)
 282 {
 283         struct symbol *type;
 284         struct range_list *left_rl, *right_rl;
 285         sval_t known;
 286
 287         if (implied != RL_IMPLIED && implied != RL_ABSOLUTE && implied != RL_REAL_ABSOLUTE)
 288                 return NULL;
 289
 290         type = get_type(expr);
 291
 292         if (get_implied_value_internal(expr->left, &known, recurse_cnt)) {
 293                 sval_t min;
 294
 295                 min = sval_lowest_set_bit(known);
 296                 left_rl = alloc_rl(min, known);
 297                 left_rl = cast_rl(type, left_rl);
 298                 add_range(&left_rl, sval_type_val(type, 0), sval_type_val(type, 0));
 299         } else {
 300                 left_rl = _get_rl(expr->left, implied, recurse_cnt);
 301                 if (left_rl) {
 302                         left_rl = cast_rl(type, left_rl);
 303                         left_rl = alloc_rl(sval_type_val(type, 0), rl_max(left_rl));
 304                 } else {
 305                         if (implied == RL_HARD)
 306                                 return NULL;
 307                         left_rl = alloc_whole_rl(type);
 308                 }
 309         }
 310
 311         if (get_implied_value_internal(expr->right, &known, recurse_cnt)) {
 312                 sval_t min, left_max, mod;
 313
 314                 min = sval_lowest_set_bit(known);
 315                 right_rl = alloc_rl(min, known);
 316                 right_rl = cast_rl(type, right_rl);
 317                 add_range(&right_rl, sval_type_val(type, 0), sval_type_val(type, 0));
 318
 319                 if (min.value != 0) {
 320                         left_max = rl_max(left_rl);
 321                         mod = sval_binop(left_max, '%', min);
 322                         if (mod.value) {
 323                                 left_max = sval_binop(left_max, '-', mod);
 324                                 left_max.value++;
 325                                 if (left_max.value > 0 && sval_cmp(left_max, rl_max(left_rl)) < 0)
 326                                         left_rl = remove_range(left_rl, left_max, rl_max(left_rl));
 327                         }
 328                 }
 329         } else {
 330                 right_rl = _get_rl(expr->right, implied, recurse_cnt);
 331                 if (right_rl) {
 332                         right_rl = cast_rl(type, right_rl);
 333                         right_rl = alloc_rl(sval_type_val(type, 0), rl_max(right_rl));
 334                 } else {
 335                         if (implied == RL_HARD)
 336                                 return NULL;
 337                         right_rl = alloc_whole_rl(type);
 338                 }
 339         }
 340
 341         return rl_intersection(left_rl, right_rl);
 342 }
 343
 344 static struct range_list *use_rl_binop(struct expression *expr, int implied, int *recurse_cnt)
 345 {
 346         struct symbol *type;
 347         struct range_list *left_rl, *right_rl;
 348
 349         if (implied != RL_IMPLIED && implied != RL_ABSOLUTE && implied != RL_REAL_ABSOLUTE)
 350                 return NULL;
 351
 352         type = get_type(expr);
 353
 354         get_absolute_rl_internal(expr->left, &left_rl, recurse_cnt);
 355         get_absolute_rl_internal(expr->right, &right_rl, recurse_cnt);
 356         left_rl = cast_rl(type, left_rl);
 357         right_rl = cast_rl(type, right_rl);
 358         if (!left_rl || !right_rl)
 359                 return NULL;
 360
 361         return rl_binop(left_rl, expr->op, right_rl);
 362 }
 363
 364 static struct range_list *handle_right_shift(struct expression *expr, int implied, int *recurse_cnt)
 365 {
 366         struct range_list *left_rl;
 367         sval_t right;
 368         sval_t min, max;
 369
 370         if (implied == RL_EXACT || implied == RL_HARD)
 371                 return NULL;
 372
 373         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 374         if (left_rl) {
 375                 max = rl_max(left_rl);
 376                 min = rl_min(left_rl);
 377         } else {
 378                 if (implied == RL_FUZZY)
 379                         return NULL;
 380                 max = sval_type_max(get_type(expr->left));
 381                 min = sval_type_val(get_type(expr->left), 0);
 382         }
 383
 384         if (get_implied_value_internal(expr->right, &right, recurse_cnt)) {
 385                 min = sval_binop(min, SPECIAL_RIGHTSHIFT, right);
 386                 max = sval_binop(max, SPECIAL_RIGHTSHIFT, right);
 387         } else if (!sval_is_negative(min)) {
 388                 min.value = 0;
 389                 max = sval_type_max(max.type);
 390         } else {
 391                 return NULL;
 392         }
 393
 394         return alloc_rl(min, max);
 395 }
 396
 397 static struct range_list *handle_left_shift(struct expression *expr, int implied, int *recurse_cnt)
 398 {
 399         struct range_list *left_rl, *res;
 400         sval_t right;
 401         sval_t min, max;
 402         int add_zero = 0;
 403
 404         if (implied == RL_EXACT || implied == RL_HARD)
 405                 return NULL;
 406         /* this is hopeless without the right side */
 407         if (!get_implied_value_internal(expr->right, &right, recurse_cnt))
 408                 return NULL;
 409         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 410         if (left_rl) {
 411                 max = rl_max(left_rl);
 412                 min = rl_min(left_rl);
 413                 if (min.value == 0) {
 414                         min.value = 1;
 415                         add_zero = 1;
 416                 }
 417         } else {
 418                 if (implied == RL_FUZZY)
 419                         return NULL;
 420                 max = sval_type_max(get_type(expr->left));
 421                 min = sval_type_val(get_type(expr->left), 1);
 422                 add_zero = 1;
 423         }
 424
 425         max = sval_binop(max, SPECIAL_LEFTSHIFT, right);
 426         min = sval_binop(min, SPECIAL_LEFTSHIFT, right);
 427         res = alloc_rl(min, max);
 428         if (add_zero)
 429                 res = rl_union(res, rl_zero());
 430         return res;
 431 }
 432
 433 static struct range_list *handle_known_binop(struct expression *expr)
 434 {
 435         sval_t left, right;
 436
 437         if (!get_value(expr->left, &left))
 438                 return NULL;
 439         if (!get_value(expr->right, &right))
 440                 return NULL;
 441         left = sval_binop(left, expr->op, right);
 442         return alloc_rl(left, left);
 443 }
 444
 445 static int has_actual_ranges(struct range_list *rl)
 446 {
 447         struct data_range *tmp;
 448
 449         FOR_EACH_PTR(rl, tmp) {
 450                 if (sval_cmp(tmp->min, tmp->max) != 0)
 451                         return 1;
 452         } END_FOR_EACH_PTR(tmp);
 453         return 0;
 454 }
 455
 456 static struct range_list *handle_implied_binop(struct range_list *left_rl, int op, struct range_list *right_rl)
 457 {
 458         struct range_list *res_rl;
 459         struct data_range *left_drange, *right_drange;
 460         sval_t res;
 461
 462         if (!left_rl || !right_rl)
 463                 return NULL;
 464         if (has_actual_ranges(left_rl))
 465                 return NULL;
 466         if (has_actual_ranges(right_rl))
 467                 return NULL;
 468
 469         if (ptr_list_size((struct ptr_list *)left_rl) * ptr_list_size((struct ptr_list *)right_rl) > 20)
 470                 return NULL;
 471
 472         res_rl = NULL;
 473
 474         FOR_EACH_PTR(left_rl, left_drange) {
 475                 FOR_EACH_PTR(right_rl, right_drange) {
 476                         if ((op == '%' || op == '/') &&
 477                             right_drange->min.value == 0)
 478                                 return NULL;
 479                         res = sval_binop(left_drange->min, op, right_drange->min);
 480                         add_range(&res_rl, res, res);
 481                 } END_FOR_EACH_PTR(right_drange);
 482         } END_FOR_EACH_PTR(left_drange);
 483
 484         return res_rl;
 485 }
 486
 487 static struct range_list *handle_binop_rl(struct expression *expr, int implied, int *recurse_cnt)
 488 {
 489         struct smatch_state *state;
 490         struct symbol *type;
 491         struct range_list *left_rl, *right_rl, *rl;
 492         sval_t min, max;
 493
 494         rl = handle_known_binop(expr);
 495         if (rl)
 496                 return rl;
 497         if (implied == RL_EXACT)
 498                 return NULL;
 499
 500         state = get_extra_state(expr);
 501         if (state && !is_whole_rl(estate_rl(state)))
 502                 return clone_rl(estate_rl(state));
 503
 504         type = get_type(expr);
 505         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 506         left_rl = cast_rl(type, left_rl);
 507         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 508         right_rl = cast_rl(type, right_rl);
 509
 510         if (!left_rl && !right_rl)
 511                 return NULL;
 512
 513         rl = handle_implied_binop(left_rl, expr->op, right_rl);
 514         if (rl)
 515                 return rl;
 516
 517         switch (expr->op) {
 518         case '%':
 519                 return handle_mod_rl(expr, implied, recurse_cnt);
 520         case '&':
 521                 return handle_bitwise_AND(expr, implied, recurse_cnt);
 522         case '|':
 523         case '^':
 524                 return use_rl_binop(expr, implied, recurse_cnt);
 525         case SPECIAL_RIGHTSHIFT:
 526                 return handle_right_shift(expr, implied, recurse_cnt);
 527         case SPECIAL_LEFTSHIFT:
 528                 return handle_left_shift(expr, implied, recurse_cnt);
 529         case '-':
 530                 return handle_subtract_rl(expr, implied, recurse_cnt);
 531         case '/':
 532                 return handle_divide_rl(expr, implied, recurse_cnt);
 533         }
 534
 535         if (!left_rl || !right_rl)
 536                 return NULL;
 537
 538         if (sval_binop_overflows(rl_min(left_rl), expr->op, rl_min(right_rl)))
 539                 return NULL;
 540         if (sval_binop_overflows(rl_max(left_rl), expr->op, rl_max(right_rl)))
 541                 return NULL;
 542
 543         min = sval_binop(rl_min(left_rl), expr->op, rl_min(right_rl));
 544         max = sval_binop(rl_max(left_rl), expr->op, rl_max(right_rl));
 545
 546         return alloc_rl(min, max);
 547 }
 548
 549 static int do_comparison(struct expression *expr)
 550 {
 551         struct range_list *left_ranges = NULL;
 552         struct range_list *right_ranges = NULL;
 553         int poss_true, poss_false;
 554         struct symbol *type;
 555
 556         type = get_type(expr);
 557         get_absolute_rl(expr->left, &left_ranges);
 558         get_absolute_rl(expr->right, &right_ranges);
 559
 560         left_ranges = cast_rl(type, left_ranges);
 561         right_ranges = cast_rl(type, right_ranges);
 562
 563         poss_true = possibly_true_rl(left_ranges, expr->op, right_ranges);
 564         poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
 565
 566         free_rl(&left_ranges);
 567         free_rl(&right_ranges);
 568
 569         if (!poss_true && !poss_false)
 570                 return 0x0;
 571         if (poss_true && !poss_false)
 572                 return 0x1;
 573         if (!poss_true && poss_false)
 574                 return 0x2;
 575         return 0x3;
 576 }
 577
 578 static struct range_list *handle_comparison_rl(struct expression *expr, int implied, int *recurse_cnt)
 579 {
 580         sval_t left, right;
 581         int res;
 582
 583         if (get_value(expr->left, &left) && get_value(expr->right, &right)) {
 584                 struct data_range tmp_left, tmp_right;
 585
 586                 tmp_left.min = left;
 587                 tmp_left.max = left;
 588                 tmp_right.min = right;
 589                 tmp_right.max = right;
 590                 if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
 591                         return rl_one();
 592                 return rl_zero();
 593         }
 594
 595         if (implied == RL_EXACT)
 596                 return NULL;
 597
 598         res = do_comparison(expr);
 599         if (res == 1)
 600                 return rl_one();
 601         if (res == 2)
 602                 return rl_zero();
 603
 604         return alloc_rl(zero, one);
 605 }
 606
 607 static struct range_list *handle_logical_rl(struct expression *expr, int implied, int *recurse_cnt)
 608 {
 609         sval_t left, right;
 610         int left_known = 0;
 611         int right_known = 0;
 612
 613         if (implied == RL_EXACT) {
 614                 if (get_value(expr->left, &left))
 615                         left_known = 1;
 616                 if (get_value(expr->right, &right))
 617                         right_known = 1;
 618         } else {
 619                 if (get_implied_value_internal(expr->left, &left, recurse_cnt))
 620                         left_known = 1;
 621                 if (get_implied_value_internal(expr->right, &right, recurse_cnt))
 622                         right_known = 1;
 623         }
 624
 625         switch (expr->op) {
 626         case SPECIAL_LOGICAL_OR:
 627                 if (left_known && left.value)
 628                         return rl_one();
 629                 if (right_known && right.value)
 630                         return rl_one();
 631                 if (left_known && right_known)
 632                         return rl_zero();
 633                 break;
 634         case SPECIAL_LOGICAL_AND:
 635                 if (left_known && right_known) {
 636                         if (left.value && right.value)
 637                                 return rl_one();
 638                         return rl_zero();
 639                 }
 640                 break;
 641         default:
 642                 return NULL;
 643         }
 644
 645         if (implied == RL_EXACT)
 646                 return NULL;
 647
 648         return alloc_rl(zero, one);
 649 }
 650
 651 static struct range_list *handle_conditional_rl(struct expression *expr, int implied, int *recurse_cnt)
 652 {
 653         struct range_list *true_rl, *false_rl;
 654         struct symbol *type;
 655         int final_pass_orig = final_pass;
 656
 657         if (known_condition_true(expr->conditional))
 658                 return _get_rl(expr->cond_true, implied, recurse_cnt);
 659         if (known_condition_false(expr->conditional))
 660                 return _get_rl(expr->cond_false, implied, recurse_cnt);
 661
 662         if (implied == RL_EXACT)
 663                 return NULL;
 664
 665         if (implied_condition_true(expr->conditional))
 666                 return _get_rl(expr->cond_true, implied, recurse_cnt);
 667         if (implied_condition_false(expr->conditional))
 668                 return _get_rl(expr->cond_false, implied, recurse_cnt);
 669
 670
 671         /* this becomes a problem with deeply nested conditional statements */
 672         if (low_on_memory())
 673                 return NULL;
 674
 675         type = get_type(expr);
 676
 677         __push_fake_cur_stree();
 678         final_pass = 0;
 679         __split_whole_condition(expr->conditional);
 680         true_rl = _get_rl(expr->cond_true, implied, recurse_cnt);
 681         __push_true_states();
 682         __use_false_states();
 683         false_rl = _get_rl(expr->cond_false, implied, recurse_cnt);
 684         __merge_true_states();
 685         __free_fake_cur_stree();
 686         final_pass = final_pass_orig;
 687
 688         if (!true_rl || !false_rl)
 689                 return NULL;
 690         true_rl = cast_rl(type, true_rl);
 691         false_rl = cast_rl(type, false_rl);
 692
 693         return rl_union(true_rl, false_rl);
 694 }
 695
 696 static int get_fuzzy_max_helper(struct expression *expr, sval_t *max)
 697 {
 698         struct smatch_state *state;
 699         sval_t sval;
 700
 701         if (get_hard_max(expr, &sval)) {
 702                 *max = sval;
 703                 return 1;
 704         }
 705
 706         state = get_extra_state(expr);
 707         if (!state || !estate_has_fuzzy_max(state))
 708                 return 0;
 709         *max = sval_cast(get_type(expr), estate_get_fuzzy_max(state));
 710         return 1;
 711 }
 712
 713 static int get_fuzzy_min_helper(struct expression *expr, sval_t *min)
 714 {
 715         struct smatch_state *state;
 716         sval_t sval;
 717
 718         state = get_extra_state(expr);
 719         if (!state || !estate_rl(state))
 720                 return 0;
 721
 722         sval = estate_min(state);
 723         if (sval_is_negative(sval) && sval_is_min(sval))
 724                 return 0;
 725
 726         if (sval_is_max(sval))
 727                 return 0;
 728
 729         *min = sval_cast(get_type(expr), sval);
 730         return 1;
 731 }
 732
 733 int get_const_value(struct expression *expr, sval_t *sval)
 734 {
 735         struct symbol *sym;
 736         sval_t right;
 737
 738         if (expr->type != EXPR_SYMBOL || !expr->symbol)
 739                 return 0;
 740         sym = expr->symbol;
 741         if (!(sym->ctype.modifiers & MOD_CONST))
 742                 return 0;
 743         if (get_value(sym->initializer, &right)) {
 744                 *sval = sval_cast(get_type(expr), right);
 745                 return 1;
 746         }
 747         return 0;
 748 }
 749
 750 struct range_list *var_to_absolute_rl(struct expression *expr)
 751 {
 752         struct smatch_state *state;
 753         struct range_list *rl;
 754
 755         state = get_extra_state(expr);
 756         if (!state || is_whole_rl(estate_rl(state))) {
 757                 state = get_real_absolute_state(expr);
 758                 if (state && state->data && !estate_is_whole(state))
 759                         return clone_rl(estate_rl(state));
 760                 if (get_local_rl(expr, &rl) && !is_whole_rl(rl))
 761                         return rl;
 762                 if (get_db_type_rl(expr, &rl) && !is_whole_rl(rl))
 763                         return rl;
 764                 return alloc_whole_rl(get_type(expr));
 765         }
 766         /* err on the side of saying things are possible */
 767         if (!estate_rl(state))
 768                 return alloc_whole_rl(get_type(expr));
 769         return clone_rl(estate_rl(state));
 770 }
 771
 772 static struct range_list *handle_variable(struct expression *expr, int implied, int *recurse_cnt)
 773 {
 774         struct smatch_state *state;
 775         struct range_list *rl;
 776         sval_t sval, min, max;
 777
 778         if (get_const_value(expr, &sval))
 779                 return alloc_rl(sval, sval);
 780
 781         if (custom_handle_variable) {
 782                 rl = custom_handle_variable(expr);
 783                 if (!rl)
 784                         return var_to_absolute_rl(expr);
 785                 return rl;
 786         }
 787
 788         switch (implied) {
 789         case RL_EXACT:
 790                 return NULL;
 791         case RL_HARD:
 792         case RL_IMPLIED:
 793         case RL_ABSOLUTE:
 794                 state = get_extra_state(expr);
 795                 if (!state || !state->data) {
 796                         if (implied == RL_HARD)
 797                                 return NULL;
 798                         if (get_local_rl(expr, &rl))
 799                                 return rl;
 800                         if (get_db_type_rl(expr, &rl))
 801                                 return rl;
 802                         return NULL;
 803                 }
 804                 if (implied == RL_HARD && !estate_has_hard_max(state))
 805                         return NULL;
 806                 return clone_rl(estate_rl(state));
 807         case RL_REAL_ABSOLUTE:
 808                 state = get_extra_state(expr);
 809                 if (!state || !state->data || is_whole_rl(estate_rl(state))) {
 810                         state = get_real_absolute_state(expr);
 811                         if (state && state->data)
 812                                 return clone_rl(estate_rl(state));
 813                         if (get_local_rl(expr, &rl))
 814                                 return rl;
 815                         if (get_db_type_rl(expr, &rl))
 816                                 return rl;
 817                         return NULL;
 818                 }
 819                 return clone_rl(estate_rl(state));
 820         case RL_FUZZY:
 821                 if (!get_fuzzy_min_helper(expr, &min))
 822                         min = sval_type_min(get_type(expr));
 823                 if (!get_fuzzy_max_helper(expr, &max))
 824                         return NULL;
 825                 /* fuzzy ranges are often inverted */
 826                 if (sval_cmp(min, max) > 0) {
 827                         sval = min;
 828                         min = max;
 829                         max = sval;
 830                 }
 831                 return alloc_rl(min, max);
 832         }
 833         return NULL;
 834 }
 835
 836 static sval_t handle_sizeof(struct expression *expr)
 837 {
 838         struct symbol *sym;
 839         sval_t ret;
 840
 841         ret = sval_blank(expr);
 842         sym = expr->cast_type;
 843         if (!sym) {
 844                 sym = evaluate_expression(expr->cast_expression);
 845                 /*
 846                  * Expressions of restricted types will possibly get
 847                  * promoted - check that here
 848                  */
 849                 if (is_restricted_type(sym)) {
 850                         if (type_bits(sym) < bits_in_int)
 851                                 sym = &int_ctype;
 852                 } else if (is_fouled_type(sym)) {
 853                         sym = &int_ctype;
 854                 }
 855         }
 856         examine_symbol_type(sym);
 857
 858         ret.type = size_t_ctype;
 859         if (type_bits(sym) <= 0) /* sizeof(void) */ {
 860                 if (get_real_base_type(sym) == &void_ctype)
 861                         ret.value = 1;
 862                 else
 863                         ret.value = 0;
 864         } else
 865                 ret.value = type_bytes(sym);
 866
 867         return ret;
 868 }
 869
 870 static struct range_list *handle_strlen(struct expression *expr, int implied, int *recurse_cnt)
 871 {
 872         struct range_list *rl;
 873         struct expression *arg;
 874         sval_t sval = { .type = &ulong_ctype };
 875
 876         if (implied == RL_EXACT)
 877                 return NULL;
 878
 879         arg = get_argument_from_call_expr(expr->args, 0);
 880         if (!arg)
 881                 return NULL;
 882         if (arg->type == EXPR_STRING) {
 883                 sval.value = arg->string->length - 1;
 884                 return alloc_rl(sval, sval);
 885         }
 886
 887         if (implied == RL_HARD || implied == RL_FUZZY)
 888                 return NULL;
 889
 890         if (get_implied_return(expr, &rl))
 891                 return rl;
 892
 893         return NULL;
 894 }
 895
 896 static struct range_list *handle_call_rl(struct expression *expr, int implied, int *recurse_cnt)
 897 {
 898         struct range_list *rl;
 899
 900         if (sym_name_is("__builtin_expect", expr->fn)) {
 901                 struct expression *arg;
 902
 903                 arg = get_argument_from_call_expr(expr->args, 0);
 904                 return _get_rl(arg, implied, recurse_cnt);
 905         }
 906
 907         if (sym_name_is("strlen", expr->fn))
 908                 return handle_strlen(expr, implied, recurse_cnt);
 909
 910         if (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY)
 911                 return NULL;
 912
 913         if (get_implied_return(expr, &rl))
 914                 return rl;
 915         return db_return_vals(expr);
 916 }
 917
 918 static struct range_list *handle_cast(struct expression *expr, int implied, int *recurse_cnt)
 919 {
 920         struct range_list *rl;
 921         struct symbol *type;
 922
 923         type = get_type(expr);
 924         rl = _get_rl(expr->cast_expression, implied, recurse_cnt);
 925         if (rl)
 926                 return cast_rl(type, rl);
 927         if (implied == RL_ABSOLUTE || implied == RL_REAL_ABSOLUTE)
 928                 return alloc_whole_rl(type);
 929         if (implied == RL_IMPLIED && type &&
 930             type_bits(type) > 0 && type_bits(type) < 32)
 931                 return alloc_whole_rl(type);
 932         return NULL;
 933 }
 934
 935 static struct range_list *_get_rl(struct expression *expr, int implied, int *recurse_cnt)
 936 {
 937         struct range_list *rl;
 938         struct symbol *type;
 939         sval_t sval;
 940
 941         type = get_type(expr);
 942         expr = strip_parens(expr);
 943         if (!expr)
 944                 return NULL;
 945
 946         if (++(*recurse_cnt) >= 200)
 947                 return NULL;
 948
 949         switch(expr->type) {
 950         case EXPR_CAST:
 951         case EXPR_FORCE_CAST:
 952         case EXPR_IMPLIED_CAST:
 953                 rl = handle_cast(expr, implied, recurse_cnt);
 954                 goto out_cast;
 955         }
 956
 957         expr = strip_expr(expr);
 958         if (!expr)
 959                 return NULL;
 960
 961         switch (expr->type) {
 962         case EXPR_VALUE:
 963                 sval = sval_from_val(expr, expr->value);
 964                 rl = alloc_rl(sval, sval);
 965                 break;
 966         case EXPR_PREOP:
 967                 rl = handle_preop_rl(expr, implied, recurse_cnt);
 968                 break;
 969         case EXPR_POSTOP:
 970                 rl = _get_rl(expr->unop, implied, recurse_cnt);
 971                 break;
 972         case EXPR_BINOP:
 973                 rl = handle_binop_rl(expr, implied, recurse_cnt);
 974                 break;
 975         case EXPR_COMPARE:
 976                 rl = handle_comparison_rl(expr, implied, recurse_cnt);
 977                 break;
 978         case EXPR_LOGICAL:
 979                 rl = handle_logical_rl(expr, implied, recurse_cnt);
 980                 break;
 981         case EXPR_PTRSIZEOF:
 982         case EXPR_SIZEOF:
 983                 sval = handle_sizeof(expr);
 984                 rl = alloc_rl(sval, sval);
 985                 break;
 986         case EXPR_SELECT:
 987         case EXPR_CONDITIONAL:
 988                 rl = handle_conditional_rl(expr, implied, recurse_cnt);
 989                 break;
 990         case EXPR_CALL:
 991                 rl = handle_call_rl(expr, implied, recurse_cnt);
 992                 break;
 993         default:
 994                 rl = handle_variable(expr, implied, recurse_cnt);
 995         }
 996
 997 out_cast:
 998         if (rl)
 999                 return rl;
1000         if (type && (implied == RL_ABSOLUTE || implied == RL_REAL_ABSOLUTE))
1001                 return alloc_whole_rl(type);
1002         return NULL;
1003 }
1004
1005 /* returns 1 if it can get a value literal or else returns 0 */
1006 int get_value(struct expression *expr, sval_t *sval)
1007 {
1008         struct range_list *rl;
1009         int recurse_cnt = 0;
1010
1011         rl = _get_rl(expr, RL_EXACT, &recurse_cnt);
1012         if (!rl_to_sval(rl, sval))
1013                 return 0;
1014         return 1;
1015 }
1016
1017 static int get_implied_value_internal(struct expression *expr, sval_t *sval, int *recurse_cnt)
1018 {
1019         struct range_list *rl;
1020
1021         rl =  _get_rl(expr, RL_IMPLIED, recurse_cnt);
1022         if (!rl_to_sval(rl, sval))
1023                 return 0;
1024         return 1;
1025 }
1026
1027 int get_implied_value(struct expression *expr, sval_t *sval)
1028 {
1029         struct range_list *rl;
1030         int recurse_cnt = 0;
1031
1032         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1033         if (!rl_to_sval(rl, sval))
1034                 return 0;
1035         return 1;
1036 }
1037
1038 int get_implied_min(struct expression *expr, sval_t *sval)
1039 {
1040         struct range_list *rl;
1041         int recurse_cnt = 0;
1042
1043         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1044         if (!rl)
1045                 return 0;
1046         *sval = rl_min(rl);
1047         return 1;
1048 }
1049
1050 int get_implied_max(struct expression *expr, sval_t *sval)
1051 {
1052         struct range_list *rl;
1053         int recurse_cnt = 0;
1054
1055         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1056         if (!rl)
1057                 return 0;
1058         *sval = rl_max(rl);
1059         return 1;
1060 }
1061
1062 int get_implied_rl(struct expression *expr, struct range_list **rl)
1063 {
1064         int recurse_cnt = 0;
1065
1066         *rl = _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1067         if (*rl)
1068                 return 1;
1069         return 0;
1070 }
1071
1072 static int get_absolute_rl_internal(struct expression *expr, struct range_list **rl, int *recurse_cnt)
1073 {
1074         *rl = _get_rl(expr, RL_ABSOLUTE, recurse_cnt);
1075         if (!*rl)
1076                 *rl = alloc_whole_rl(get_type(expr));
1077         return 1;
1078 }
1079
1080 int get_absolute_rl(struct expression *expr, struct range_list **rl)
1081 {
1082         int recurse_cnt = 0;
1083
1084         *rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1085         if (!*rl)
1086                 *rl = alloc_whole_rl(get_type(expr));
1087         return 1;
1088 }
1089
1090 int get_real_absolute_rl(struct expression *expr, struct range_list **rl)
1091 {
1092         int recurse_cnt = 0;
1093
1094         *rl = _get_rl(expr, RL_REAL_ABSOLUTE, &recurse_cnt);
1095         if (!*rl)
1096                 *rl = alloc_whole_rl(get_type(expr));
1097         return 1;
1098 }
1099
1100 int custom_get_absolute_rl(struct expression *expr,
1101                            struct range_list *(*fn)(struct expression *expr),
1102                            struct range_list **rl)
1103 {
1104         int recurse_cnt = 0;
1105
1106         *rl = NULL;
1107         custom_handle_variable = fn;
1108         *rl = _get_rl(expr, RL_REAL_ABSOLUTE, &recurse_cnt);
1109         custom_handle_variable = NULL;
1110         return 1;
1111 }
1112
1113 int get_implied_rl_var_sym(const char *var, struct symbol *sym, struct range_list **rl)
1114 {
1115         struct smatch_state *state;
1116
1117         state = get_state(SMATCH_EXTRA, var, sym);
1118         *rl = estate_rl(state);
1119         if (*rl)
1120                 return 1;
1121         return 0;
1122 }
1123
1124 int get_hard_max(struct expression *expr, sval_t *sval)
1125 {
1126         struct range_list *rl;
1127         int recurse_cnt = 0;
1128
1129         rl =  _get_rl(expr, RL_HARD, &recurse_cnt);
1130         if (!rl)
1131                 return 0;
1132         *sval = rl_max(rl);
1133         return 1;
1134 }
1135
1136 int get_fuzzy_min(struct expression *expr, sval_t *sval)
1137 {
1138         struct range_list *rl;
1139         sval_t tmp;
1140         int recurse_cnt = 0;
1141
1142         rl =  _get_rl(expr, RL_FUZZY, &recurse_cnt);
1143         if (!rl)
1144                 return 0;
1145         tmp = rl_min(rl);
1146         if (sval_is_negative(tmp) && sval_is_min(tmp))
1147                 return 0;
1148         *sval = tmp;
1149         return 1;
1150 }
1151
1152 int get_fuzzy_max(struct expression *expr, sval_t *sval)
1153 {
1154         struct range_list *rl;
1155         sval_t max;
1156         int recurse_cnt = 0;
1157
1158         rl =  _get_rl(expr, RL_FUZZY, &recurse_cnt);
1159         if (!rl)
1160                 return 0;
1161         max = rl_max(rl);
1162         if (max.uvalue > INT_MAX - 10000)
1163                 return 0;
1164         *sval = max;
1165         return 1;
1166 }
1167
1168 int get_absolute_min(struct expression *expr, sval_t *sval)
1169 {
1170         struct range_list *rl;
1171         struct symbol *type;
1172         int recurse_cnt = 0;
1173
1174         type = get_type(expr);
1175         if (!type)
1176                 type = &llong_ctype;  // FIXME: this is wrong but places assume get type can't fail.
1177         rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1178         if (rl)
1179                 *sval = rl_min(rl);
1180         else
1181                 *sval = sval_type_min(type);
1182
1183         if (sval_cmp(*sval, sval_type_min(type)) < 0)
1184                 *sval = sval_type_min(type);
1185         return 1;
1186 }
1187
1188 int get_absolute_max(struct expression *expr, sval_t *sval)
1189 {
1190         struct range_list *rl;
1191         struct symbol *type;
1192         int recurse_cnt = 0;
1193
1194         type = get_type(expr);
1195         if (!type)
1196                 type = &llong_ctype;
1197         rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1198         if (rl)
1199                 *sval = rl_max(rl);
1200         else
1201                 *sval = sval_type_max(type);
1202
1203         if (sval_cmp(sval_type_max(type), *sval) < 0)
1204                 *sval = sval_type_max(type);
1205         return 1;
1206 }
1207
1208 int known_condition_true(struct expression *expr)
1209 {
1210         sval_t tmp;
1211
1212         if (!expr)
1213                 return 0;
1214
1215         if (get_value(expr, &tmp) && tmp.value)
1216                 return 1;
1217
1218         return 0;
1219 }
1220
1221 int known_condition_false(struct expression *expr)
1222 {
1223         if (!expr)
1224                 return 0;
1225
1226         if (is_zero(expr))
1227                 return 1;
1228
1229         if (expr->type == EXPR_CALL) {
1230                 if (sym_name_is("__builtin_constant_p", expr->fn))
1231                         return 1;
1232         }
1233         return 0;
1234 }
1235
1236 int implied_condition_true(struct expression *expr)
1237 {
1238         sval_t tmp;
1239
1240         if (!expr)
1241                 return 0;
1242
1243         if (known_condition_true(expr))
1244                 return 1;
1245         if (get_implied_value(expr, &tmp) && tmp.value)
1246                 return 1;
1247
1248         if (expr->type == EXPR_POSTOP)
1249                 return implied_condition_true(expr->unop);
1250
1251         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_DECREMENT)
1252                 return implied_not_equal(expr->unop, 1);
1253         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_INCREMENT)
1254                 return implied_not_equal(expr->unop, -1);
1255
1256         expr = strip_expr(expr);
1257         switch (expr->type) {
1258         case EXPR_COMPARE:
1259                 if (do_comparison(expr) == 1)
1260                         return 1;
1261                 break;
1262         case EXPR_PREOP:
1263                 if (expr->op == '!') {
1264                         if (implied_condition_false(expr->unop))
1265                                 return 1;
1266                         break;
1267                 }
1268                 break;
1269         default:
1270                 if (implied_not_equal(expr, 0) == 1)
1271                         return 1;
1272                 break;
1273         }
1274         return 0;
1275 }
1276
1277 int implied_condition_false(struct expression *expr)
1278 {
1279         struct expression *tmp;
1280         sval_t sval;
1281
1282         if (!expr)
1283                 return 0;
1284
1285         if (known_condition_false(expr))
1286                 return 1;
1287
1288         switch (expr->type) {
1289         case EXPR_COMPARE:
1290                 if (do_comparison(expr) == 2)
1291                         return 1;
1292         case EXPR_PREOP:
1293                 if (expr->op == '!') {
1294                         if (implied_condition_true(expr->unop))
1295                                 return 1;
1296                         break;
1297                 }
1298                 tmp = strip_expr(expr);
1299                 if (tmp != expr)
1300                         return implied_condition_false(tmp);
1301                 break;
1302         default:
1303                 if (get_implied_value(expr, &sval) && sval.value == 0)
1304                         return 1;
1305                 break;
1306         }
1307         return 0;
1308 }
1309
1310 int can_integer_overflow(struct symbol *type, struct expression *expr)
1311 {
1312         int op;
1313         sval_t lmax, rmax, res;
1314
1315         if (!type)
1316                 type = &int_ctype;
1317
1318         expr = strip_expr(expr);
1319
1320         if (expr->type == EXPR_ASSIGNMENT) {
1321                 switch(expr->op) {
1322                 case SPECIAL_MUL_ASSIGN:
1323                         op = '*';
1324                         break;
1325                 case SPECIAL_ADD_ASSIGN:
1326                         op = '+';
1327                         break;
1328                 case SPECIAL_SHL_ASSIGN:
1329                         op = SPECIAL_LEFTSHIFT;
1330                         break;
1331                 default:
1332                         return 0;
1333                 }
1334         } else if (expr->type == EXPR_BINOP) {
1335                 if (expr->op != '*' && expr->op != '+' && expr->op != SPECIAL_LEFTSHIFT)
1336                         return 0;
1337                 op = expr->op;
1338         } else {
1339                 return 0;
1340         }
1341
1342         get_absolute_max(expr->left, &lmax);
1343         get_absolute_max(expr->right, &rmax);
1344
1345         if (sval_binop_overflows(lmax, op, rmax))
1346                 return 1;
1347
1348         res = sval_binop(lmax, op, rmax);
1349         if (sval_cmp(res, sval_type_max(type)) > 0)
1350                 return 1;
1351         return 0;
1352 }