smatch_equiv.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 /*
  19  * smatch_equiv.c is for tracking how variables are the same
  20  *
  21  * if (a == b) {
  22  * Or
  23  * x = y;
  24  *
  25  * When a variable gets modified all the old relationships are
  26  * deleted.  remove_equiv(expr);
  27  *
  28  */
  29
  30 #include "smatch.h"
  31 #include "smatch_slist.h"
  32 #include "smatch_extra.h"
  33
  34 ALLOCATOR(relation, "related variables");
  35
  36 static struct relation *alloc_relation(const char *name, struct symbol *sym)
  37 {
  38         struct relation *tmp;
  39
  40         tmp = __alloc_relation(0);
  41         tmp->name = alloc_string(name);
  42         tmp->sym = sym;
  43         return tmp;
  44 }
  45
  46 struct related_list *clone_related_list(struct related_list *related)
  47 {
  48         struct relation *rel;
  49         struct related_list *to_list = NULL;
  50
  51         FOR_EACH_PTR(related, rel) {
  52                 add_ptr_list(&to_list, rel);
  53         } END_FOR_EACH_PTR(rel);
  54
  55         return to_list;
  56 }
  57
  58 static int cmp_relation(struct relation *a, struct relation *b)
  59 {
  60         int ret;
  61
  62         if (a == b)
  63                 return 0;
  64
  65         if (a->sym > b->sym)
  66                 return -1;
  67         if (a->sym < b->sym)
  68                 return 1;
  69
  70         ret = strcmp(a->name, b->name);
  71         if (ret)
  72                 return ret;
  73
  74         return 0;
  75 }
  76
  77 struct related_list *get_shared_relations(struct related_list *one,
  78                                               struct related_list *two)
  79 {
  80         struct related_list *ret = NULL;
  81         struct relation *one_rel;
  82         struct relation *two_rel;
  83
  84         PREPARE_PTR_LIST(one, one_rel);
  85         PREPARE_PTR_LIST(two, two_rel);
  86         for (;;) {
  87                 if (!one_rel || !two_rel)
  88                         break;
  89                 if (cmp_relation(one_rel, two_rel) < 0) {
  90                         NEXT_PTR_LIST(one_rel);
  91                 } else if (cmp_relation(one_rel, two_rel) == 0) {
  92                         add_ptr_list(&ret, one_rel);
  93                         NEXT_PTR_LIST(one_rel);
  94                         NEXT_PTR_LIST(two_rel);
  95                 } else {
  96                         NEXT_PTR_LIST(two_rel);
  97                 }
  98         }
  99         FINISH_PTR_LIST(two_rel);
 100         FINISH_PTR_LIST(one_rel);
 101
 102         return ret;
 103 }
 104
 105 static void add_related(struct related_list **rlist, const char *name, struct symbol *sym)
 106 {
 107         struct relation *rel;
 108         struct relation *new;
 109         struct relation tmp = {
 110                 .name = (char *)name,
 111                 .sym = sym
 112         };
 113
 114         FOR_EACH_PTR(*rlist, rel) {
 115                 if (cmp_relation(rel, &tmp) < 0)
 116                         continue;
 117                 if (cmp_relation(rel, &tmp) == 0)
 118                         return;
 119                 new = alloc_relation(name, sym);
 120                 INSERT_CURRENT(new, rel);
 121                 return;
 122         } END_FOR_EACH_PTR(rel);
 123         new = alloc_relation(name, sym);
 124         add_ptr_list(rlist, new);
 125 }
 126
 127 static struct related_list *del_related(struct smatch_state *state, const char *name, struct symbol *sym)
 128 {
 129         struct relation *tmp;
 130         struct relation remove = {
 131                 .name = (char *)name,
 132                 .sym = sym,
 133         };
 134         struct related_list *ret = NULL;
 135
 136         FOR_EACH_PTR(estate_related(state), tmp) {
 137                 if (cmp_relation(tmp, &remove) != 0)
 138                         add_ptr_list(&ret, tmp);
 139         } END_FOR_EACH_PTR(tmp);
 140
 141         return ret;
 142 }
 143
 144 void remove_from_equiv(const char *name, struct symbol *sym)
 145 {
 146         struct sm_state *orig_sm;
 147         struct relation *rel;
 148         struct smatch_state *state;
 149         struct related_list *to_update;
 150
 151         orig_sm = get_sm_state(SMATCH_EXTRA, name, sym);
 152         if (!orig_sm || !get_dinfo(orig_sm->state)->related)
 153                 return;
 154
 155         state = clone_estate(orig_sm->state);
 156         to_update = del_related(state, name, sym);
 157
 158         FOR_EACH_PTR(to_update, rel) {
 159                 struct sm_state *old_sm, *new_sm;
 160
 161                 old_sm = get_sm_state(SMATCH_EXTRA, rel->name, rel->sym);
 162                 if (!old_sm)
 163                         continue;
 164
 165                 new_sm = clone_sm(old_sm);
 166                 get_dinfo(new_sm->state)->related = to_update;
 167                 __set_sm(new_sm);
 168         } END_FOR_EACH_PTR(rel);
 169 }
 170
 171 void set_related(struct smatch_state *estate, struct related_list *rlist)
 172 {
 173         if (!estate_related(estate) && !rlist)
 174                 return;
 175         get_dinfo(estate)->related = rlist;
 176 }
 177
 178 /*
 179  * set_equiv() is only used for assignments where we set one variable
 180  * equal to the other.  a = b;.  It's not used for if conditions where
 181  * a == b.
 182  */
 183 void set_equiv(struct expression *left, struct expression *right)
 184 {
 185         struct sm_state *right_sm, *left_sm, *other_sm;
 186         struct relation *rel;
 187         char *left_name;
 188         struct symbol *left_sym;
 189         struct related_list *rlist;
 190         char *other_name;
 191         struct symbol *other_sym;
 192
 193         left_name = expr_to_var_sym(left, &left_sym);
 194         if (!left_name || !left_sym)
 195                 goto free;
 196
 197         other_name = get_other_name_sym(left_name, left_sym, &other_sym);
 198
 199         right_sm = get_sm_state_expr(SMATCH_EXTRA, right);
 200         if (!right_sm) {
 201                 struct range_list *rl;
 202
 203                 if (!get_implied_rl(right, &rl))
 204                         rl = alloc_whole_rl(get_type(right));
 205                 right_sm = set_state_expr(SMATCH_EXTRA, right, alloc_estate_rl(rl));
 206         }
 207         if (!right_sm)
 208                 goto free;
 209
 210         /* This block is because we want to preserve the implications. */
 211         left_sm = clone_sm(right_sm);
 212         left_sm->name = alloc_string(left_name);
 213         left_sm->sym = left_sym;
 214         left_sm->state = clone_estate_cast(get_type(left), right_sm->state);
 215         /* FIXME: The expression we're passing is wrong */
 216         set_extra_mod_helper(left_name, left_sym, left, left_sm->state);
 217         __set_sm(left_sm);
 218
 219         if (other_name && other_sym) {
 220                 other_sm = clone_sm(right_sm);
 221                 other_sm->name = alloc_string(other_name);
 222                 other_sm->sym = other_sym;
 223                 other_sm->state = clone_estate_cast(get_type(left), left_sm->state);
 224                 set_extra_mod_helper(other_name, other_sym, NULL, other_sm->state);
 225                 __set_sm(other_sm);
 226         }
 227
 228         rlist = clone_related_list(estate_related(right_sm->state));
 229         add_related(&rlist, right_sm->name, right_sm->sym);
 230         add_related(&rlist, left_name, left_sym);
 231         if (other_name && other_sym)
 232                 add_related(&rlist, other_name, other_sym);
 233
 234         FOR_EACH_PTR(rlist, rel) {
 235                 struct sm_state *old_sm, *new_sm;
 236
 237                 old_sm = get_sm_state(SMATCH_EXTRA, rel->name, rel->sym);
 238                 if (!old_sm)  /* shouldn't happen */
 239                         continue;
 240                 new_sm = clone_sm(old_sm);
 241                 new_sm->state = clone_estate(old_sm->state);
 242                 get_dinfo(new_sm->state)->related = rlist;
 243                 __set_sm(new_sm);
 244         } END_FOR_EACH_PTR(rel);
 245 free:
 246         free_string(left_name);
 247 }
 248
 249 void set_equiv_state_expr(int id, struct expression *expr, struct smatch_state *state)
 250 {
 251         struct relation *rel;
 252         struct smatch_state *estate;
 253
 254         estate = get_state_expr(SMATCH_EXTRA, expr);
 255
 256         if (!estate)
 257                 return;
 258
 259         FOR_EACH_PTR(get_dinfo(estate)->related, rel) {
 260                 set_state(id, rel->name, rel->sym, state);
 261         } END_FOR_EACH_PTR(rel);
 262 }