smatch_extra.c

   1 /*
   2  * sparse/smatch_extra.c
   3  *
   4  * Copyright (C) 2008 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * smatch_extra.c is supposed to track the value of every variable.
  12  */
  13
  14 #include <stdlib.h>
  15 #define __USE_ISOC99
  16 #include <limits.h>
  17 #include "parse.h"
  18 #include "smatch.h"
  19 #include "smatch_slist.h"
  20 #include "smatch_extra.h"
  21
  22 static int my_id;
  23
  24 static struct symbol *cur_func;
  25
  26 struct data_range whole_range = {
  27         .min = LLONG_MIN,
  28         .max = LLONG_MAX,
  29 };
  30
  31 static struct smatch_state *alloc_extra_state_empty()
  32 {
  33         struct smatch_state *state;
  34         struct data_info *dinfo;
  35
  36         dinfo = __alloc_data_info(0);
  37         dinfo->type = DATA_RANGE;
  38         dinfo->value_ranges = NULL;
  39         state = __alloc_smatch_state(0);
  40         state->data = dinfo;
  41         return state;
  42 }
  43
  44 static struct smatch_state *alloc_extra_state_no_name(int val)
  45 {
  46         struct smatch_state *state;
  47
  48         state = __alloc_smatch_state(0);
  49         state->data = (void *)alloc_dinfo_range(val, val);
  50         return state;
  51 }
  52
  53 /* We do this because ->value_ranges is a list */
  54 struct smatch_state *extra_undefined()
  55 {
  56         struct data_info *dinfo;
  57         static struct smatch_state *ret;
  58         static struct symbol *prev_func;
  59
  60         if  (prev_func == cur_func)
  61                 return ret;
  62         prev_func = cur_func;
  63
  64         dinfo = alloc_dinfo_range(whole_range.min, whole_range.max);
  65         ret = __alloc_smatch_state(0);
  66         ret->name = "unknown";
  67         ret->data = dinfo;
  68         return ret;
  69 }
  70
  71 struct smatch_state *alloc_extra_state(int val)
  72 {
  73         struct smatch_state *state;
  74
  75         state = alloc_extra_state_no_name(val);
  76         state->name = show_ranges(((struct data_info *)state->data)->value_ranges);
  77         return state;
  78 }
  79
  80 struct smatch_state *alloc_extra_state_range(long long min, long long max)
  81 {
  82         struct smatch_state *state;
  83
  84         if (min == whole_range.min && max == whole_range.max)
  85                 return extra_undefined();
  86         state = __alloc_smatch_state(0);
  87         state->data = (void *)alloc_dinfo_range(min, max);
  88         state->name = show_ranges(((struct data_info *)state->data)->value_ranges);
  89         return state;
  90 }
  91
  92 struct smatch_state *alloc_extra_state_range_list(struct range_list *rl)
  93 {
  94         struct smatch_state *state;
  95
  96         state = __alloc_smatch_state(0);
  97         state->data = (void *)alloc_dinfo_range_list(rl);
  98         state->name = show_ranges(((struct data_info *)state->data)->value_ranges);
  99         return state;
 100 }
 101
 102 struct smatch_state *filter_range(struct smatch_state *orig,
 103                                  long long filter_min, long long filter_max)
 104 {
 105         struct smatch_state *ret;
 106         struct data_info *orig_info;
 107         struct data_info *ret_info;
 108
 109         if (!orig)
 110                 orig = extra_undefined();
 111         orig_info = (struct data_info *)orig->data;
 112         ret = alloc_extra_state_empty();
 113         ret_info = (struct data_info *)ret->data;
 114         ret_info->value_ranges = remove_range(orig_info->value_ranges, filter_min, filter_max);
 115         ret->name = show_ranges(ret_info->value_ranges);
 116         return ret;
 117 }
 118
 119 struct smatch_state *add_filter(struct smatch_state *orig, long long num)
 120 {
 121         return filter_range(orig, num, num);
 122 }
 123
 124 static struct smatch_state *merge_func(const char *name, struct symbol *sym,
 125                                        struct smatch_state *s1,
 126                                        struct smatch_state *s2)
 127 {
 128         struct data_info *info1 = (struct data_info *)s1->data;
 129         struct data_info *info2 = (struct data_info *)s2->data;
 130         struct data_info *ret_info;
 131         struct smatch_state *tmp;
 132         struct range_list *value_ranges;
 133
 134         value_ranges = range_list_union(info1->value_ranges, info2->value_ranges);
 135         tmp = alloc_extra_state_empty();
 136         ret_info = (struct data_info *)tmp->data;
 137         ret_info->value_ranges = value_ranges;
 138         tmp->name = show_ranges(ret_info->value_ranges);
 139         return tmp;
 140 }
 141
 142 struct sm_state *__extra_pre_loop_hook_before(struct statement *iterator_pre_statement)
 143 {
 144         struct expression *expr;
 145         char *name;
 146         struct symbol *sym;
 147         struct sm_state *ret = NULL;
 148
 149         if (!iterator_pre_statement)
 150                 return NULL;
 151         if (iterator_pre_statement->type != STMT_EXPRESSION)
 152                 return NULL;
 153         expr = iterator_pre_statement->expression;
 154         if (expr->type != EXPR_ASSIGNMENT)
 155                 return NULL;
 156         name = get_variable_from_expr(expr->left, &sym);
 157         if (!name || !sym)
 158                 goto free;
 159         ret = get_sm_state(my_id, name, sym);
 160 free:
 161         free_string(name);
 162         return ret;
 163 }
 164
 165 int __iterator_unchanged(struct sm_state *sm, struct statement *iterator)
 166 {
 167         struct expression *iter_expr;
 168         char *name;
 169         struct symbol *sym;
 170         int ret = 0;
 171
 172         if (!iterator)
 173                 return 0;
 174         if (iterator->type != STMT_EXPRESSION)
 175                 return 0;
 176         iter_expr = iterator->expression;
 177         if (iter_expr->op != SPECIAL_INCREMENT && iter_expr->op != SPECIAL_DECREMENT)
 178                 return 0;
 179         name = get_variable_from_expr(iter_expr->unop, &sym);
 180         if (!name || !sym)
 181                 goto free;
 182         if (get_sm_state(my_id, name, sym) == sm)
 183                 ret = 1;
 184 free:
 185         free_string(name);
 186         return ret;
 187 }
 188
 189 void __extra_pre_loop_hook_after(struct sm_state *sm,
 190                                 struct statement *iterator,
 191                                 struct expression *condition)
 192 {
 193         struct expression *iter_expr;
 194         char *name;
 195         struct symbol *sym;
 196         long long value;
 197         int left = 0;
 198         struct smatch_state *state;
 199         struct data_info *dinfo;
 200         long long min, max;
 201
 202         iter_expr = iterator->expression;
 203
 204         if (condition->type != EXPR_COMPARE)
 205                 return;
 206         if (!get_value(condition->left, &value)) {
 207                 if (!get_value(condition->right, &value))
 208                         return;
 209                 left = 1;
 210         }
 211         if (left)
 212                 name = get_variable_from_expr(condition->left, &sym);
 213         else
 214                 name = get_variable_from_expr(condition->right, &sym);
 215         if (!name || !sym)
 216                 goto free;
 217         if (sym != sm->sym || strcmp(name, sm->name))
 218                 goto free;
 219         state = get_state(my_id, name, sym);
 220         dinfo = (struct data_info *)state->data;
 221         min = get_dinfo_min(dinfo);
 222         max = get_dinfo_max(dinfo);
 223         if (iter_expr->op == SPECIAL_INCREMENT && min != whole_range.min && max == whole_range.max) {
 224                 set_state(my_id, name, sym, alloc_extra_state(min));
 225         } else if (min == whole_range.min && max != whole_range.max) {
 226                 set_state(my_id, name, sym, alloc_extra_state(max));
 227         }
 228 free:
 229         free_string(name);
 230         return;
 231 }
 232
 233 static struct smatch_state *unmatched_state(struct sm_state *sm)
 234 {
 235         return extra_undefined();
 236 }
 237
 238 static void match_function_call(struct expression *expr)
 239 {
 240         struct expression *tmp;
 241         struct symbol *sym;
 242         char *name;
 243         int i = 0;
 244
 245         FOR_EACH_PTR(expr->args, tmp) {
 246                 if (tmp->op == '&') {
 247                         name = get_variable_from_expr(tmp->unop, &sym);
 248                         if (name) {
 249                                 set_state(my_id, name, sym, extra_undefined());
 250                         }
 251                         free_string(name);
 252                 }
 253                 i++;
 254         } END_FOR_EACH_PTR(tmp);
 255 }
 256
 257 static void match_assign(struct expression *expr)
 258 {
 259         struct expression *left;
 260         struct symbol *sym;
 261         char *name;
 262         long long value;
 263         int known;
 264         long long min = whole_range.min;
 265         long long max = whole_range.max;
 266         long long tmp;
 267
 268         left = strip_expr(expr->left);
 269         name = get_variable_from_expr(left, &sym);
 270         if (!name)
 271                 return;
 272         known = get_value(expr->right, &value);
 273
 274         if (expr->op == '=') {
 275                 if (known)
 276                         set_state(my_id, name, sym, alloc_extra_state(value));
 277                 else
 278                         set_state(my_id, name, sym, extra_undefined());
 279                 goto free;
 280         }
 281         if (expr->op == SPECIAL_ADD_ASSIGN) {
 282                 if (get_implied_min(expr->unop, &tmp)) {
 283                         if (known)
 284                                 min = tmp + value;
 285                         else
 286                                 min = tmp;
 287                 }
 288
 289         }
 290         if (expr->op == SPECIAL_SUB_ASSIGN) {
 291                 if (get_implied_max(expr->unop, &tmp)) {
 292                         if (known)
 293                                 max = tmp - value;
 294                         else
 295                                 max = tmp;
 296                 }
 297
 298         }
 299         set_state(my_id, name, sym, alloc_extra_state_range(min, max));
 300 free:
 301         free_string(name);
 302 }
 303
 304 static void undef_expr(struct expression *expr)
 305 {
 306         struct symbol *sym;
 307         char *name;
 308         long long min = whole_range.min;
 309         long long max = whole_range.max;
 310         long long val;
 311
 312         if (expr->op == '*')
 313                 return;
 314         if (expr->op == '(')
 315                 return;
 316
 317         name = get_variable_from_expr(expr->unop, &sym);
 318         if (!name)
 319                 goto free;
 320         if (expr->op == SPECIAL_INCREMENT) {
 321                 if (get_implied_min(expr->unop, &val))
 322                         min = val + 1;
 323         }
 324         if (expr->op == SPECIAL_DECREMENT) {
 325                 if (get_implied_max(expr->unop, &val))
 326                         max = val - 1;
 327         }
 328         set_state(my_id, name, sym, alloc_extra_state_range(min, max));
 329 free:
 330         free_string(name);
 331 }
 332
 333 static void match_declarations(struct symbol *sym)
 334 {
 335         const char *name;
 336         long long val;
 337
 338         if (sym->ident) {
 339                 name = sym->ident->name;
 340                 if (sym->initializer) {
 341                         if (get_value(sym->initializer, &val))
 342                                 set_state(my_id, name, sym, alloc_extra_state(val));
 343                         else
 344                                 set_state(my_id, name, sym, extra_undefined());
 345                         scoped_state(name, my_id, sym);
 346                 } else {
 347                         set_state(my_id, name, sym, extra_undefined());
 348                         scoped_state(name, my_id, sym);
 349                 }
 350         }
 351 }
 352
 353 static void match_function_def(struct symbol *sym)
 354 {
 355         struct symbol *arg;
 356
 357         cur_func = sym;
 358         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 359                 if (!arg->ident) {
 360                         continue;
 361                 }
 362                 set_state(my_id, arg->ident->name, arg, extra_undefined());
 363         } END_FOR_EACH_PTR(arg);
 364 }
 365
 366 #define VAL_SINGLE 0
 367 #define VAL_MAX    1
 368 #define VAL_MIN    2
 369
 370 static int get_implied_value_helper(struct expression *expr, long long *val, int what)
 371 {
 372         struct smatch_state *state;
 373         struct symbol *sym;
 374         char *name;
 375
 376         if (get_value(expr, val))
 377                 return 1;
 378
 379         name = get_variable_from_expr(expr, &sym);
 380         if (!name)
 381                 return 0;
 382         state = get_state(my_id, name, sym);
 383         free_string(name);
 384         if (!state || !state->data)
 385                 return 0;
 386         if (what == VAL_SINGLE)
 387                 return get_single_value_from_range((struct data_info *)state->data, val);
 388         if (what == VAL_MAX) {
 389                 *val = get_dinfo_max((struct data_info *)state->data);
 390                 if (*val == whole_range.max) /* this means just guessing */
 391                         return 0;
 392                 return 1;
 393         }
 394         *val = get_dinfo_min((struct data_info *)state->data);
 395         if (*val == whole_range.min)
 396                 return 0;
 397         return 1;
 398 }
 399
 400 int get_implied_single_val(struct expression *expr, long long *val)
 401 {
 402         return get_implied_value_helper(expr, val, VAL_SINGLE);
 403 }
 404
 405 int get_implied_max(struct expression *expr, long long *val)
 406 {
 407         return get_implied_value_helper(expr, val, VAL_MAX);
 408 }
 409
 410 int get_implied_min(struct expression *expr, long long *val)
 411 {
 412         return get_implied_value_helper(expr, val, VAL_MIN);
 413 }
 414
 415 static int last_stmt_val(struct statement *stmt, long long *val)
 416 {
 417         struct expression *expr;
 418
 419         if (!stmt)
 420                 return 0;
 421
 422         stmt = last_ptr_list((struct ptr_list *)stmt->stmts);
 423         if (stmt->type != STMT_EXPRESSION)
 424                 return 0;
 425         expr = stmt->expression;
 426         return get_value(expr, val);
 427 }
 428
 429 static void match_comparison(struct expression *expr)
 430 {
 431         long long fixed;
 432         char *name = NULL;
 433         struct symbol *sym;
 434         struct smatch_state *one_state;
 435         struct smatch_state *two_state;
 436         struct smatch_state *orig;
 437         int left = 0;
 438         int comparison = expr->op;
 439         struct expression *varies = expr->right;
 440
 441         if (!get_value(expr->left, &fixed)) {
 442                 if (!get_value(expr->right, &fixed))
 443                         return;
 444                 varies = expr->left;
 445                 left = 1;
 446         }
 447         if (varies->type == EXPR_PREOP || varies->type == EXPR_POSTOP) {
 448                 varies = varies->unop;
 449         }
 450         if (varies->type == EXPR_CALL) {
 451                 function_comparison(comparison, varies, fixed, left);
 452                 return;
 453         }
 454         name = get_variable_from_expr(varies, &sym);
 455         if (!name || !sym)
 456                 goto free;
 457
 458         orig = get_state(my_id, name, sym);
 459         if (!orig)
 460                 orig = extra_undefined();
 461
 462         switch(comparison){
 463         case '<':
 464         case SPECIAL_UNSIGNED_LT:
 465                 one_state = filter_range(orig, whole_range.min, fixed - 1);
 466                 two_state = filter_range(orig, fixed, whole_range.max);
 467                 if (left)
 468                         set_true_false_states(my_id, name, sym, two_state, one_state);
 469                 else
 470                         set_true_false_states(my_id, name, sym, one_state, two_state);
 471                 return;
 472         case SPECIAL_UNSIGNED_LTE:
 473         case SPECIAL_LTE:
 474                 one_state = filter_range(orig, whole_range.min, fixed);
 475                 two_state = filter_range(orig, fixed + 1, whole_range.max);
 476                 if (left)
 477                         set_true_false_states(my_id, name, sym, two_state, one_state);
 478                 else
 479                         set_true_false_states(my_id, name, sym, one_state, two_state);
 480                 return;
 481         case SPECIAL_EQUAL:
 482                 // todo.  print a warning here for impossible conditions.
 483                 one_state = alloc_extra_state(fixed);
 484                 two_state = filter_range(orig, fixed, fixed);
 485                 set_true_false_states(my_id, name, sym, one_state, two_state);
 486                 return;
 487         case SPECIAL_UNSIGNED_GTE:
 488         case SPECIAL_GTE:
 489                 one_state = filter_range(orig, whole_range.min, fixed - 1);
 490                 two_state = filter_range(orig, fixed, whole_range.max);
 491                 if (left)
 492                         set_true_false_states(my_id, name, sym, one_state, two_state);
 493                 else
 494                         set_true_false_states(my_id, name, sym, two_state, one_state);
 495                 return;
 496         case '>':
 497         case SPECIAL_UNSIGNED_GT:
 498                 one_state = filter_range(orig, whole_range.min, fixed);
 499                 two_state = filter_range(orig, fixed + 1, whole_range.max);
 500                 if (left)
 501                         set_true_false_states(my_id, name, sym, one_state, two_state);
 502                 else
 503                         set_true_false_states(my_id, name, sym, two_state, one_state);
 504                 return;
 505         case SPECIAL_NOTEQUAL:
 506                 one_state = alloc_extra_state(fixed);
 507                 two_state = filter_range(orig, fixed, fixed);
 508                 set_true_false_states(my_id, name, sym, two_state, one_state);
 509                 return;
 510         default:
 511                 sm_msg("unhandled comparison %d\n", comparison);
 512                 return;
 513         }
 514         return;
 515 free:
 516         free_string(name);
 517 }
 518
 519 /* this is actually hooked from smatch_implied.c...  it's hacky, yes */
 520 void __extra_match_condition(struct expression *expr)
 521 {
 522         struct symbol *sym;
 523         char *name;
 524         struct smatch_state *pre_state;
 525         struct smatch_state *true_state;
 526         struct smatch_state *false_state;
 527
 528         expr = strip_expr(expr);
 529         switch(expr->type) {
 530         case EXPR_CALL:
 531                 function_comparison(SPECIAL_NOTEQUAL, expr, 0, 1);
 532                 return;
 533         case EXPR_PREOP:
 534         case EXPR_SYMBOL:
 535         case EXPR_DEREF:
 536                 name = get_variable_from_expr(expr, &sym);
 537                 if (!name)
 538                         return;
 539                 pre_state = get_state(my_id, name, sym);
 540                 true_state = add_filter(pre_state, 0);
 541                 false_state = alloc_extra_state(0);
 542                 set_true_false_states(my_id, name, sym, true_state, false_state);
 543                 free_string(name);
 544                 return;
 545         case EXPR_COMPARE:
 546                 match_comparison(expr);
 547                 return;
 548         case EXPR_ASSIGNMENT:
 549                 __extra_match_condition(expr->right);
 550                 __extra_match_condition(expr->left);
 551                 return;
 552         }
 553 }
 554
 555 /* returns 1 if it is not possible for expr to be value, otherwise returns 0 */
 556 int implied_not_equal(struct expression *expr, long long val)
 557 {
 558         char *name;
 559         struct symbol *sym;
 560         struct smatch_state *state;
 561         int ret = 0;
 562
 563         name = get_variable_from_expr(expr, &sym);
 564         if (!name || !sym)
 565                 goto exit;
 566         state = get_state(my_id, name, sym);
 567         if (!state || !state->data)
 568                 goto exit;
 569         ret = !possibly_false(SPECIAL_NOTEQUAL, (struct data_info *)state->data, val, 1);
 570 exit:
 571         free_string(name);
 572         return ret;
 573 }
 574
 575 int known_condition_true(struct expression *expr)
 576 {
 577         long long tmp;
 578
 579         if (!expr)
 580                 return 0;
 581
 582         if (get_value(expr, &tmp) && tmp)
 583                 return 1;
 584
 585         expr = strip_expr(expr);
 586         switch(expr->type) {
 587         case EXPR_PREOP:
 588                 if (expr->op == '!') {
 589                         if (known_condition_false(expr->unop))
 590                                 return 1;
 591                         break;
 592                 }
 593                 break;
 594         default:
 595                 break;
 596         }
 597         return 0;
 598 }
 599
 600 int known_condition_false(struct expression *expr)
 601 {
 602         if (!expr)
 603                 return 0;
 604
 605         if (is_zero(expr))
 606                 return 1;
 607
 608         switch(expr->type) {
 609         case EXPR_PREOP:
 610                 if (expr->op == '!') {
 611                         if (known_condition_true(expr->unop))
 612                                 return 1;
 613                         break;
 614                 }
 615                 break;
 616         default:
 617                 break;
 618         }
 619         return 0;
 620 }
 621
 622 static int do_comparison_range(struct expression *expr)
 623 {
 624         struct symbol *sym;
 625         char *name;
 626         struct smatch_state *state;
 627         long long value;
 628         int left = 0;
 629         int poss_true, poss_false;
 630
 631         if (!get_value(expr->left, &value)) {
 632                 if (!get_value(expr->right, &value))
 633                         return 3;
 634                 left = 1;
 635         }
 636         if (left)
 637                 name = get_variable_from_expr(expr->left, &sym);
 638         else
 639                 name = get_variable_from_expr(expr->right, &sym);
 640         if (!name || !sym)
 641                 goto free;
 642         state = get_state(SMATCH_EXTRA, name, sym);
 643         if (!state)
 644                 goto free;
 645         poss_true = possibly_true(expr->op, (struct data_info *)state->data, value, left);
 646         poss_false = possibly_false(expr->op, (struct data_info *)state->data, value, left);
 647         if (!poss_true && !poss_false)
 648                 return 0;
 649         if (poss_true && !poss_false)
 650                 return 1;
 651         if (!poss_true && poss_false)
 652                 return 2;
 653         if (poss_true && poss_false)
 654                 return 3;
 655 free:
 656         free_string(name);
 657         return 3;
 658 }
 659
 660 int implied_condition_true(struct expression *expr)
 661 {
 662         struct statement *stmt;
 663         long long tmp;
 664         long long val;
 665
 666         if (!expr)
 667                 return 0;
 668
 669         if (get_value(expr, &tmp) && tmp)
 670                 return 1;
 671
 672         expr = strip_expr(expr);
 673         switch(expr->type) {
 674         case EXPR_COMPARE:
 675                 if (do_comparison_range(expr) == 1)
 676                         return 1;
 677                 break;
 678         case EXPR_PREOP:
 679                 if (expr->op == '!') {
 680                         if (implied_condition_false(expr->unop))
 681                                 return 1;
 682                         break;
 683                 }
 684                 stmt = get_block_thing(expr);
 685                 if (last_stmt_val(stmt, &val) && val == 1)
 686                         return 1;
 687                 break;
 688         default:
 689                 if (implied_not_equal(expr, 0) == 1)
 690                         return 1;
 691                 break;
 692         }
 693         return 0;
 694 }
 695
 696 int implied_condition_false(struct expression *expr)
 697 {
 698         struct statement *stmt;
 699         struct expression *tmp;
 700         long long val;
 701
 702         if (!expr)
 703                 return 0;
 704
 705         if (is_zero(expr))
 706                 return 1;
 707
 708         switch(expr->type) {
 709         case EXPR_COMPARE:
 710                 if (do_comparison_range(expr) == 2)
 711                         return 1;
 712         case EXPR_PREOP:
 713                 if (expr->op == '!') {
 714                         if (implied_condition_true(expr->unop))
 715                                 return 1;
 716                         break;
 717                 }
 718                 stmt = get_block_thing(expr);
 719                 if (last_stmt_val(stmt, &val) && val == 0)
 720                         return 1;
 721                 tmp = strip_expr(expr);
 722                 if (tmp != expr)
 723                         return implied_condition_false(tmp);
 724                 break;
 725         default:
 726                 if (get_implied_value(expr, &val) && val == 0)
 727                         return 1;
 728                 break;
 729         }
 730         return 0;
 731 }
 732
 733 void register_smatch_extra(int id)
 734 {
 735         my_id = id;
 736         add_merge_hook(my_id, &merge_func);
 737         add_unmatched_state_hook(my_id, &unmatched_state);
 738         add_hook(&undef_expr, OP_HOOK);
 739         add_hook(&match_function_def, FUNC_DEF_HOOK);
 740         add_hook(&match_function_call, FUNCTION_CALL_HOOK);
 741         add_hook(&match_assign, ASSIGNMENT_HOOK);
 742         add_hook(&match_declarations, DECLARATION_HOOK);
 743
 744         if (option_project == PROJ_KERNEL) {
 745                 /* I don't know how to test for the ATTRIB_NORET attribute. :( */
 746                 add_function_hook("panic", &__match_nullify_path_hook, NULL);
 747                 add_function_hook("do_exit", &__match_nullify_path_hook, NULL);
 748                 add_function_hook("complete_and_exit", &__match_nullify_path_hook, NULL);
 749                 add_function_hook("__module_put_and_exit", &__match_nullify_path_hook, NULL);
 750                 add_function_hook("do_group_exit", &__match_nullify_path_hook, NULL);
 751         }
 752 }