smatch_helper.c

   1 /*
   2  * Copyright (C) 2006 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 /*
  19  * Miscellaneous helper functions.
  20  */
  21
  22 #include <stdlib.h>
  23 #include <stdio.h>
  24 #include "allocate.h"
  25 #include "smatch.h"
  26 #include "smatch_extra.h"
  27
  28 #define VAR_LEN 512
  29
  30 char *alloc_string(const char *str)
  31 {
  32         char *tmp;
  33
  34         if (!str)
  35                 return NULL;
  36         tmp = malloc(strlen(str) + 1);
  37         strcpy(tmp, str);
  38         return tmp;
  39 }
  40
  41 void free_string(char *str)
  42 {
  43         free(str);
  44 }
  45
  46 void remove_parens(char *str)
  47 {
  48         char *src, *dst;
  49
  50         dst = src = str;
  51         while (*src != '\0') {
  52                 if (*src == '(' || *src == ')') {
  53                         src++;
  54                         continue;
  55                 }
  56                 *dst++ = *src++;
  57         }
  58         *dst = *src;
  59 }
  60
  61 struct smatch_state *alloc_state_num(int num)
  62 {
  63         struct smatch_state *state;
  64         static char buff[256];
  65
  66         state = __alloc_smatch_state(0);
  67         snprintf(buff, 255, "%d", num);
  68         buff[255] = '\0';
  69         state->name = alloc_string(buff);
  70         state->data = INT_PTR(num);
  71         return state;
  72 }
  73
  74 struct smatch_state *alloc_state_str(const char *name)
  75 {
  76         struct smatch_state *state;
  77
  78         state = __alloc_smatch_state(0);
  79         state->name = alloc_string(name);
  80         return state;
  81 }
  82
  83 void append(char *dest, const char *data, int buff_len)
  84 {
  85         strncat(dest, data, buff_len - strlen(dest) - 1);
  86 }
  87
  88 /*
  89  * If you have "foo(a, b, 1);" then use
  90  * get_argument_from_call_expr(expr, 0) to return the expression for
  91  * a.  Yes, it does start counting from 0.
  92  */
  93 struct expression *get_argument_from_call_expr(struct expression_list *args,
  94                                                int num)
  95 {
  96         struct expression *expr;
  97         int i = 0;
  98
  99         if (!args)
 100                 return NULL;
 101
 102         FOR_EACH_PTR(args, expr) {
 103                 if (i == num)
 104                         return expr;
 105                 i++;
 106         } END_FOR_EACH_PTR(expr);
 107         return NULL;
 108 }
 109
 110 static struct expression *get_array_expr(struct expression *expr)
 111 {
 112         struct symbol *type;
 113
 114         if (expr->type != EXPR_BINOP || expr->op != '+')
 115                 return NULL;
 116
 117         type = get_type(expr->left);
 118         if (!type || type->type != SYM_ARRAY)
 119                 return NULL;
 120         return expr->left;
 121 }
 122
 123 static void __get_variable_from_expr(struct symbol **sym_ptr, char *buf,
 124                                      struct expression *expr, int len,
 125                                      int *complicated, int no_parens)
 126 {
 127         switch (expr->type) {
 128         case EXPR_DEREF: {
 129                 struct expression *deref;
 130                 int op;
 131
 132                 deref = expr->deref;
 133                 op = deref->op;
 134                 if (op == '*') {
 135                         struct expression *unop = strip_expr(deref->unop);
 136
 137                         if (unop->type == EXPR_PREOP && unop->op == '&') {
 138                                 deref = unop->unop;
 139                                 op = '.';
 140                         } else {
 141                                 deref = deref->unop;
 142                         }
 143                 }
 144
 145                 __get_variable_from_expr(sym_ptr, buf, deref, len, complicated, no_parens);
 146
 147                 if (op == '*')
 148                         append(buf, "->", len);
 149                 else
 150                         append(buf, ".", len);
 151
 152                 if (expr->member)
 153                         append(buf, expr->member->name, len);
 154                 else
 155                         append(buf, "unknown_member", len);
 156
 157                 return;
 158         }
 159         case EXPR_SYMBOL:
 160                 if (expr->symbol_name)
 161                         append(buf, expr->symbol_name->name, len);
 162                 if (sym_ptr) {
 163                         if (*sym_ptr)
 164                                 *complicated = 1;
 165                         *sym_ptr = expr->symbol;
 166                 }
 167                 return;
 168         case EXPR_PREOP: {
 169                 const char *tmp;
 170
 171                 if (get_expression_statement(expr)) {
 172                         *complicated = 2;
 173                         return;
 174                 }
 175
 176                 if (expr->op == '(') {
 177                         if (!no_parens)
 178                                 append(buf, "(", len);
 179                 } else if (expr->op != '*' || !get_array_expr(expr->unop)) {
 180                         tmp = show_special(expr->op);
 181                         append(buf, tmp, len);
 182                 }
 183                 __get_variable_from_expr(sym_ptr, buf, expr->unop,
 184                                                  len, complicated, no_parens);
 185
 186                 if (expr->op == '(' && !no_parens)
 187                         append(buf, ")", len);
 188
 189                 if (expr->op == SPECIAL_DECREMENT ||
 190                                 expr->op == SPECIAL_INCREMENT)
 191                         *complicated = 1;
 192
 193                 return;
 194         }
 195         case EXPR_POSTOP: {
 196                 const char *tmp;
 197
 198                 __get_variable_from_expr(sym_ptr, buf, expr->unop,
 199                                                  len, complicated, no_parens);
 200                 tmp = show_special(expr->op);
 201                 append(buf, tmp, len);
 202
 203                 if (expr->op == SPECIAL_DECREMENT || expr->op == SPECIAL_INCREMENT)
 204                         *complicated = 1;
 205                 return;
 206         }
 207         case EXPR_ASSIGNMENT:
 208         case EXPR_COMPARE:
 209         case EXPR_LOGICAL:
 210         case EXPR_BINOP: {
 211                 char tmp[10];
 212                 struct expression *array_expr;
 213
 214                 *complicated = 1;
 215                 array_expr = get_array_expr(expr);
 216                 if (array_expr) {
 217                         __get_variable_from_expr(sym_ptr, buf, array_expr, len, complicated, no_parens);
 218                         append(buf, "[", len);
 219                 } else {
 220                         __get_variable_from_expr(sym_ptr, buf, expr->left, len, complicated, no_parens);
 221                         snprintf(tmp, sizeof(tmp), " %s ", show_special(expr->op));
 222                         append(buf, tmp, len);
 223                 }
 224                 __get_variable_from_expr(NULL, buf, expr->right, len, complicated, no_parens);
 225                 if (array_expr)
 226                         append(buf, "]", len);
 227                 return;
 228         }
 229         case EXPR_VALUE: {
 230                 char tmp[25];
 231
 232                 *complicated = 1;
 233                 snprintf(tmp, 25, "%lld", expr->value);
 234                 append(buf, tmp, len);
 235                 return;
 236         }
 237         case EXPR_STRING:
 238                 append(buf, "\"", len);
 239                 if (expr->string)
 240                         append(buf, expr->string->data, len);
 241                 append(buf, "\"", len);
 242                 return;
 243         case EXPR_CALL: {
 244                 struct expression *tmp;
 245                 int i;
 246
 247                 *complicated = 1;
 248                 __get_variable_from_expr(NULL, buf, expr->fn, len, complicated, no_parens);
 249                 append(buf, "(", len);
 250                 i = 0;
 251                 FOR_EACH_PTR(expr->args, tmp) {
 252                         if (i++)
 253                                 append(buf, ", ", len);
 254                         __get_variable_from_expr(NULL, buf, tmp, len, complicated, no_parens);
 255                 } END_FOR_EACH_PTR(tmp);
 256                 append(buf, ")", len);
 257                 return;
 258         }
 259         case EXPR_CAST:
 260         case EXPR_FORCE_CAST:
 261                 __get_variable_from_expr(sym_ptr, buf,
 262                                          expr->cast_expression, len,
 263                                          complicated, no_parens);
 264                 return;
 265         case EXPR_SIZEOF: {
 266                 int size;
 267                 char tmp[25];
 268
 269                 if (expr->cast_type && get_base_type(expr->cast_type)) {
 270                         size = type_bytes(get_base_type(expr->cast_type));
 271                         snprintf(tmp, 25, "%d", size);
 272                         append(buf, tmp, len);
 273                 }
 274                 return;
 275         }
 276         case EXPR_IDENTIFIER:
 277                 *complicated = 1;
 278                 if (expr->expr_ident)
 279                         append(buf, expr->expr_ident->name, len);
 280                 return;
 281         default:
 282                 *complicated = 1;
 283                 //printf("unknown type = %d\n", expr->type);
 284                 return;
 285         }
 286 }
 287
 288 /*
 289  * This is returns a stylized "c looking" representation of the
 290  * variable name.
 291  *
 292  * It uses the same buffer every time so you have to save the result
 293  * yourself if you want to keep it.
 294  *
 295  */
 296
 297 char *expr_to_str_sym(struct expression *expr, struct symbol **sym_ptr)
 298 {
 299         static char var_name[VAR_LEN];
 300         int complicated = 0;
 301
 302         if (sym_ptr)
 303                 *sym_ptr = NULL;
 304         var_name[0] = '\0';
 305
 306         if (!expr)
 307                 return NULL;
 308         __get_variable_from_expr(sym_ptr, var_name, expr, sizeof(var_name),
 309                                  &complicated, 0);
 310         if (complicated < 2)
 311                 return alloc_string(var_name);
 312         else
 313                 return NULL;
 314 }
 315
 316 char *expr_to_str(struct expression *expr)
 317 {
 318         return expr_to_str_sym(expr, NULL);
 319 }
 320
 321 /*
 322  * get_variable_from_expr_simple() only returns simple variables.
 323  * If it's a complicated variable like a->foo[x] instead of just 'a->foo'
 324  * then it returns NULL.
 325  */
 326 char *expr_to_var_sym(struct expression *expr,
 327                                     struct symbol **sym_ptr)
 328 {
 329         static char var_name[VAR_LEN];
 330         int complicated = 0;
 331
 332         if (sym_ptr)
 333                 *sym_ptr = NULL;
 334         var_name[0] = '\0';
 335
 336         if (!expr)
 337                 return NULL;
 338         expr = strip_expr(expr);
 339         __get_variable_from_expr(sym_ptr, var_name, expr, sizeof(var_name),
 340                                  &complicated, 1);
 341
 342         if (complicated) {
 343                 if (sym_ptr)
 344                         *sym_ptr = NULL;
 345                 return NULL;
 346         }
 347         return alloc_string(var_name);
 348 }
 349
 350 char *expr_to_var(struct expression *expr)
 351 {
 352         return expr_to_var_sym(expr, NULL);
 353 }
 354
 355 struct symbol *expr_to_sym(struct expression *expr)
 356 {
 357         struct symbol *sym;
 358         char *name;
 359
 360         name = expr_to_var_sym(expr, &sym);
 361         free_string(name);
 362         return sym;
 363 }
 364
 365 int get_complication_score(struct expression *expr)
 366 {
 367         int score = 0;
 368
 369         expr = strip_expr(expr);
 370
 371         /*
 372          * Don't forget to keep get_complication_score() and store_all_links()
 373          * in sync.
 374          *
 375          */
 376
 377         switch (expr->type) {
 378         case EXPR_CALL:
 379                 return 999;
 380         case EXPR_COMPARE:
 381         case EXPR_BINOP:
 382                 score += get_complication_score(expr->left);
 383                 score += get_complication_score(expr->right);
 384                 return score;
 385         case EXPR_SYMBOL:
 386                 if (is_local_variable(expr))
 387                         return 1;
 388                 return 999;
 389         case EXPR_PREOP:
 390                 if (expr->op == '*')
 391                         return score + get_complication_score(expr->unop);
 392                 return 999;
 393         case EXPR_DEREF:
 394                 return score + get_complication_score(expr->deref);
 395         case EXPR_VALUE:
 396                 return 0;
 397         default:
 398                 return 999;
 399         }
 400 }
 401
 402 char *expr_to_chunk_helper(struct expression *expr, struct symbol **sym, struct var_sym_list **vsl)
 403 {
 404         char *name;
 405         struct symbol *tmp;
 406
 407         if (vsl)
 408                 *vsl = NULL;
 409
 410         expr = strip_parens(expr);
 411         if (!expr)
 412                 return NULL;
 413         if (sym)
 414                 *sym = NULL;
 415
 416         name = expr_to_var_sym(expr, &tmp);
 417         if (name && tmp) {
 418                 if (sym)
 419                         *sym = tmp;
 420                 if (vsl)
 421                         *vsl = expr_to_vsl(expr);
 422                 return name;
 423         }
 424         free_string(name);
 425
 426         if (get_complication_score(expr) > 2)
 427                 return NULL;
 428
 429         if (vsl) {
 430                 *vsl = expr_to_vsl(expr);
 431                 if (!*vsl)
 432                         return NULL;
 433         }
 434
 435         return expr_to_str(expr);
 436 }
 437
 438 char *expr_to_known_chunk_sym(struct expression *expr, struct symbol **sym)
 439 {
 440         return expr_to_chunk_helper(expr, sym, NULL);
 441 }
 442
 443 char *expr_to_chunk_sym_vsl(struct expression *expr, struct symbol **sym, struct var_sym_list **vsl)
 444 {
 445         return expr_to_chunk_helper(expr, sym, vsl);
 446 }
 447
 448 int sym_name_is(const char *name, struct expression *expr)
 449 {
 450         if (!expr)
 451                 return 0;
 452         if (expr->type != EXPR_SYMBOL)
 453                 return 0;
 454         if (!strcmp(expr->symbol_name->name, name))
 455                 return 1;
 456         return 0;
 457 }
 458
 459 int is_zero(struct expression *expr)
 460 {
 461         sval_t sval;
 462
 463         if (get_value(expr, &sval) && sval.value == 0)
 464                 return 1;
 465         return 0;
 466 }
 467
 468 int is_array(struct expression *expr)
 469 {
 470         struct symbol *type;
 471
 472         expr = strip_expr(expr);
 473         if (!expr)
 474                 return 0;
 475
 476         if (expr->type == EXPR_PREOP && expr->op == '*') {
 477                 expr = strip_expr(expr->unop);
 478                 if (expr->type == EXPR_BINOP && expr->op == '+')
 479                         return 1;
 480         }
 481
 482         if (expr->type != EXPR_BINOP || expr->op != '+')
 483                 return 0;
 484
 485         type = get_type(expr->left);
 486         if (!type || type->type != SYM_ARRAY)
 487                 return 0;
 488
 489         return 1;
 490 }
 491
 492 struct expression *get_array_base(struct expression *expr)
 493 {
 494         if (!is_array(expr))
 495                 return NULL;
 496         expr = strip_expr(expr);
 497         if (expr->type == EXPR_PREOP && expr->op == '*')
 498                 expr = strip_expr(expr->unop);
 499         if (expr->type != EXPR_BINOP || expr->op != '+')
 500                 return NULL;
 501         return strip_parens(expr->left);
 502 }
 503
 504 struct expression *get_array_offset(struct expression *expr)
 505 {
 506         if (!is_array(expr))
 507                 return NULL;
 508         expr = strip_expr(expr);
 509         if (expr->type == EXPR_PREOP && expr->op == '*')
 510                 expr = strip_expr(expr->unop);
 511         if (expr->type != EXPR_BINOP || expr->op != '+')
 512                 return NULL;
 513         return strip_parens(expr->right);
 514 }
 515
 516 const char *show_state(struct smatch_state *state)
 517 {
 518         if (!state)
 519                 return NULL;
 520         return state->name;
 521 }
 522
 523 struct statement *get_expression_statement(struct expression *expr)
 524 {
 525         /* What are those things called? if (({....; ret;})) { ...*/
 526
 527         if (expr->type != EXPR_PREOP)
 528                 return NULL;
 529         if (expr->op != '(')
 530                 return NULL;
 531         if (expr->unop->type != EXPR_STATEMENT)
 532                 return NULL;
 533         if (expr->unop->statement->type != STMT_COMPOUND)
 534                 return NULL;
 535         return expr->unop->statement;
 536 }
 537
 538 struct expression *strip_parens(struct expression *expr)
 539 {
 540         if (!expr)
 541                 return NULL;
 542
 543         if (expr->type == EXPR_PREOP) {
 544                 if (expr->op == '(' && expr->unop->type == EXPR_STATEMENT &&
 545                         expr->unop->statement->type == STMT_COMPOUND)
 546                         return expr;
 547                 if (expr->op == '(')
 548                         return strip_parens(expr->unop);
 549         }
 550         return expr;
 551 }
 552
 553 struct expression *strip_expr(struct expression *expr)
 554 {
 555         if (!expr)
 556                 return NULL;
 557
 558         switch (expr->type) {
 559         case EXPR_FORCE_CAST:
 560         case EXPR_CAST:
 561                 return strip_expr(expr->cast_expression);
 562         case EXPR_PREOP: {
 563                 struct expression *unop;
 564
 565                 if (expr->op == '(' && expr->unop->type == EXPR_STATEMENT &&
 566                         expr->unop->statement->type == STMT_COMPOUND)
 567                         return expr;
 568
 569                 unop = strip_expr(expr->unop);
 570
 571                 if (expr->op == '*' &&
 572                     unop->type == EXPR_PREOP && unop->op == '&') {
 573                         struct symbol *type = get_type(unop->unop);
 574
 575                         if (type && type->type == SYM_ARRAY)
 576                                 return expr;
 577                         return strip_expr(unop->unop);
 578                 }
 579
 580                 if (expr->op == '(')
 581                         return unop;
 582
 583                 return expr;
 584         }
 585         case EXPR_CONDITIONAL:
 586                 if (known_condition_true(expr->conditional)) {
 587                         if (expr->cond_true)
 588                                 return strip_expr(expr->cond_true);
 589                         return strip_expr(expr->conditional);
 590                 }
 591                 if (known_condition_false(expr->conditional))
 592                         return strip_expr(expr->cond_false);
 593                 return expr;
 594         case EXPR_CALL:
 595                 if (sym_name_is("__builtin_expect", expr->fn)) {
 596                         expr = get_argument_from_call_expr(expr->args, 0);
 597                         return strip_expr(expr);
 598                 }
 599                 return expr;
 600         }
 601         return expr;
 602 }
 603
 604 static void delete_state_tracker(struct tracker *t)
 605 {
 606         delete_state(t->owner, t->name, t->sym);
 607         __free_tracker(t);
 608 }
 609
 610 void scoped_state(int my_id, const char *name, struct symbol *sym)
 611 {
 612         struct tracker *t;
 613
 614         t = alloc_tracker(my_id, name, sym);
 615         add_scope_hook((scope_hook *)&delete_state_tracker, t);
 616 }
 617
 618 int is_error_return(struct expression *expr)
 619 {
 620         struct symbol *cur_func = cur_func_sym;
 621         sval_t sval;
 622
 623         if (!expr)
 624                 return 0;
 625         if (cur_func->type != SYM_NODE)
 626                 return 0;
 627         cur_func = get_base_type(cur_func);
 628         if (cur_func->type != SYM_FN)
 629                 return 0;
 630         cur_func = get_base_type(cur_func);
 631         if (cur_func == &void_ctype)
 632                 return 0;
 633         if (!get_implied_value(expr, &sval))
 634                 return 0;
 635         if (sval.value < 0)
 636                 return 1;
 637         if (cur_func->type == SYM_PTR && sval.value == 0)
 638                 return 1;
 639         return 0;
 640 }
 641
 642 int getting_address(void)
 643 {
 644         struct expression *tmp;
 645         int i = 0;
 646         int dot_ops = 0;
 647
 648         FOR_EACH_PTR_REVERSE(big_expression_stack, tmp) {
 649                 if (!i++)
 650                         continue;
 651                 if (tmp->type == EXPR_PREOP && tmp->op == '(')
 652                         continue;
 653                 if (tmp->op == '.' && !dot_ops++)
 654                         continue;
 655                 if (tmp->op == '&')
 656                         return 1;
 657                 return 0;
 658         } END_FOR_EACH_PTR_REVERSE(tmp);
 659         return 0;
 660 }
 661
 662 char *get_member_name(struct expression *expr)
 663 {
 664         char buf[256];
 665         struct symbol *sym;
 666
 667         expr = strip_expr(expr);
 668         if (expr->type != EXPR_DEREF)
 669                 return NULL;
 670         if (!expr->member)
 671                 return NULL;
 672
 673         sym = get_type(expr->deref);
 674         if (!sym)
 675                 return NULL;
 676         if (sym->type == SYM_UNION) {
 677                 sym = expr_to_sym(expr->deref);
 678                 sym = get_real_base_type(sym);
 679                 if (sym && sym->type == SYM_PTR)
 680                         sym = get_real_base_type(sym);
 681                 if (!sym || !sym->ident) {
 682                         snprintf(buf, sizeof(buf), "(union hack)->%s", expr->member->name);
 683                         return alloc_string(buf);
 684                 }
 685         }
 686         if (!sym->ident)
 687                 return NULL;
 688         snprintf(buf, sizeof(buf), "(struct %s)->%s", sym->ident->name, expr->member->name);
 689         return alloc_string(buf);
 690 }
 691
 692 int cmp_pos(struct position pos1, struct position pos2)
 693 {
 694         /* the stream position is ... */
 695         if (pos1.stream > pos2.stream)
 696                 return -1;
 697         if (pos1.stream < pos2.stream)
 698                 return 1;
 699
 700         if (pos1.line < pos2.line)
 701                 return -1;
 702         if (pos1.line > pos2.line)
 703                 return 1;
 704
 705         if (pos1.pos < pos2.pos)
 706                 return -1;
 707         if (pos1.pos > pos2.pos)
 708                 return 1;
 709
 710         return 0;
 711 }
 712
 713 int positions_eq(struct position pos1, struct position pos2)
 714 {
 715         if (pos1.line != pos2.line)
 716                 return 0;
 717         if (pos1.pos != pos2.pos)
 718                 return 0;
 719         if (pos1.stream != pos2.stream)
 720                 return 0;
 721         return 1;
 722 }
 723
 724 struct statement *get_current_statement(void)
 725 {
 726         struct statement *prev, *tmp;
 727
 728         prev = last_ptr_list((struct ptr_list *)big_statement_stack);
 729
 730         if (!prev || !get_macro_name(prev->pos))
 731                 return prev;
 732
 733         FOR_EACH_PTR_REVERSE(big_statement_stack, tmp) {
 734                 if (positions_eq(tmp->pos, prev->pos))
 735                         continue;
 736                 if (prev->pos.line > tmp->pos.line)
 737                         return prev;
 738                 return tmp;
 739         } END_FOR_EACH_PTR_REVERSE(tmp);
 740         return prev;
 741 }
 742
 743 struct statement *get_prev_statement(void)
 744 {
 745         struct statement *tmp;
 746         int i;
 747
 748         i = 0;
 749         FOR_EACH_PTR_REVERSE(big_statement_stack, tmp) {
 750                 if (i++ == 1)
 751                         return tmp;
 752         } END_FOR_EACH_PTR_REVERSE(tmp);
 753         return NULL;
 754 }
 755
 756 int get_param_num_from_sym(struct symbol *sym)
 757 {
 758         struct symbol *tmp;
 759         int i;
 760
 761         if (!cur_func_sym)
 762                 return -1;
 763
 764         i = 0;
 765         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, tmp) {
 766                 if (tmp == sym)
 767                         return i;
 768                 i++;
 769         } END_FOR_EACH_PTR(tmp);
 770         return -1;
 771 }
 772
 773 int get_param_num(struct expression *expr)
 774 {
 775         struct symbol *sym;
 776         char *name;
 777
 778         if (!cur_func_sym)
 779                 return -1;
 780         name = expr_to_var_sym(expr, &sym);
 781         free_string(name);
 782         if (!sym)
 783                 return -1;
 784         return get_param_num_from_sym(sym);
 785 }
 786
 787 int ms_since(struct timeval *start)
 788 {
 789         struct timeval end;
 790         double diff;
 791
 792         gettimeofday(&end, NULL);
 793         diff = (end.tv_sec - start->tv_sec) * 1000.0;
 794         diff += (end.tv_usec - start->tv_usec) / 1000.0;
 795         return (int)diff;
 796 }
 797
 798 int parent_is_gone_var_sym(const char *name, struct symbol *sym)
 799 {
 800         if (!name || !sym)
 801                 return 0;
 802
 803         if (parent_is_null_var_sym(name, sym) ||
 804             parent_is_free_var_sym(name, sym))
 805                 return 1;
 806         return 0;
 807 }
 808
 809 int parent_is_gone(struct expression *expr)
 810 {
 811         struct symbol *sym;
 812         char *var;
 813         int ret = 0;
 814
 815         expr = strip_expr(expr);
 816         var = expr_to_var_sym(expr, &sym);
 817         if (!var || !sym)
 818                 goto free;
 819         ret = parent_is_gone_var_sym(var, sym);
 820 free:
 821         free_string(var);
 822         return ret;
 823 }
 824
 825 int invert_op(int op)
 826 {
 827         switch (op) {
 828         case '*':
 829                 return '/';
 830         case '/':
 831                 return '*';
 832         case '+':
 833                 return '-';
 834         case '-':
 835                 return '+';
 836         case SPECIAL_LEFTSHIFT:
 837                 return SPECIAL_RIGHTSHIFT;
 838         case SPECIAL_RIGHTSHIFT:
 839                 return SPECIAL_LEFTSHIFT;
 840         }
 841         return 0;
 842 }