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 debug_addition(struct related_list *rlist, const char *name)
 106 {
 107         struct relation *tmp;
 108
 109         if (!option_debug_related)
 110                 return;
 111
 112         sm_prefix();
 113         sm_printf("(");
 114         FOR_EACH_PTR(rlist, tmp) {
 115                 sm_printf("%s ", tmp->name);
 116         } END_FOR_EACH_PTR(tmp);
 117         sm_printf(") <-- %s\n", name);
 118 }
 119
 120 static void add_related(struct related_list **rlist, const char *name, struct symbol *sym)
 121 {
 122         struct relation *rel;
 123         struct relation *new;
 124         struct relation tmp = {
 125                 .name = (char *)name,
 126                 .sym = sym
 127         };
 128
 129         debug_addition(*rlist, name);
 130
 131         FOR_EACH_PTR(*rlist, rel) {
 132                 if (cmp_relation(rel, &tmp) < 0)
 133                         continue;
 134                 if (cmp_relation(rel, &tmp) == 0)
 135                         return;
 136                 new = alloc_relation(name, sym);
 137                 INSERT_CURRENT(new, rel);
 138                 return;
 139         } END_FOR_EACH_PTR(rel);
 140         new = alloc_relation(name, sym);
 141         add_ptr_list(rlist, new);
 142 }
 143
 144 static struct related_list *del_related(struct smatch_state *state, const char *name, struct symbol *sym)
 145 {
 146         struct relation *tmp;
 147         struct relation remove = {
 148                 .name = (char *)name,
 149                 .sym = sym,
 150         };
 151         struct related_list *ret = NULL;
 152
 153         FOR_EACH_PTR(estate_related(state), tmp) {
 154                 if (cmp_relation(tmp, &remove) != 0)
 155                         add_ptr_list(&ret, tmp);
 156         } END_FOR_EACH_PTR(tmp);
 157
 158         return ret;
 159 }
 160
 161 void remove_from_equiv(const char *name, struct symbol *sym)
 162 {
 163         struct sm_state *orig_sm;
 164         struct relation *rel;
 165         struct smatch_state *state;
 166         struct related_list *to_update;
 167
 168         orig_sm = get_sm_state(SMATCH_EXTRA, name, sym);
 169         if (!orig_sm || !get_dinfo(orig_sm->state)->related)
 170                 return;
 171
 172         state = clone_estate(orig_sm->state);
 173         to_update = del_related(state, name, sym);
 174
 175         FOR_EACH_PTR(to_update, rel) {
 176                 struct sm_state *old_sm, *new_sm;
 177
 178                 old_sm = get_sm_state(SMATCH_EXTRA, rel->name, rel->sym);
 179                 if (!old_sm)
 180                         continue;
 181
 182                 new_sm = clone_sm(old_sm);
 183                 get_dinfo(new_sm->state)->related = to_update;
 184                 __set_sm(new_sm);
 185         } END_FOR_EACH_PTR(rel);
 186 }
 187
 188 void remove_from_equiv_expr(struct expression *expr)
 189 {
 190         char *name;
 191         struct symbol *sym;
 192
 193         name = expr_to_var_sym(expr, &sym);
 194         if (!name || !sym)
 195                 goto free;
 196         remove_from_equiv(name, sym);
 197 free:
 198         free_string(name);
 199 }
 200
 201 void set_related(struct smatch_state *estate, struct related_list *rlist)
 202 {
 203         if (!estate_related(estate) && !rlist)
 204                 return;
 205         get_dinfo(estate)->related = rlist;
 206 }
 207
 208 /*
 209  * set_equiv() is only used for assignments where we set one variable
 210  * equal to the other.  a = b;.  It's not used for if conditions where
 211  * a == b.
 212  */
 213 void set_equiv(struct expression *left, struct expression *right)
 214 {
 215         struct sm_state *right_sm, *left_sm;
 216         struct relation *rel;
 217         char *left_name;
 218         struct symbol *left_sym;
 219         struct related_list *rlist;
 220
 221         left_name = expr_to_var_sym(left, &left_sym);
 222         if (!left_name || !left_sym)
 223                 goto free;
 224
 225         right_sm = get_sm_state_expr(SMATCH_EXTRA, right);
 226         if (!right_sm)
 227                 right_sm = set_state_expr(SMATCH_EXTRA, right, alloc_estate_whole(get_type(right)));
 228         if (!right_sm)
 229                 goto free;
 230
 231         /* This block is because we want to preserve the implications. */
 232         left_sm = clone_sm(right_sm);
 233         left_sm->name = alloc_string(left_name);
 234         left_sm->sym = left_sym;
 235         left_sm->state = clone_estate_cast(get_type(left), right_sm->state);
 236         set_extra_mod_helper(left_name, left_sym, left, left_sm->state);
 237         __set_sm(left_sm);
 238
 239         rlist = clone_related_list(estate_related(right_sm->state));
 240         add_related(&rlist, right_sm->name, right_sm->sym);
 241         add_related(&rlist, left_name, left_sym);
 242
 243         FOR_EACH_PTR(rlist, rel) {
 244                 struct sm_state *old_sm, *new_sm;
 245
 246                 old_sm = get_sm_state(SMATCH_EXTRA, rel->name, rel->sym);
 247                 if (!old_sm)  /* shouldn't happen */
 248                         continue;
 249                 new_sm = clone_sm(old_sm);
 250                 new_sm->state = clone_estate(old_sm->state);
 251                 get_dinfo(new_sm->state)->related = rlist;
 252                 __set_sm(new_sm);
 253         } END_FOR_EACH_PTR(rel);
 254 free:
 255         free_string(left_name);
 256 }
 257
 258 void set_equiv_state_expr(int id, struct expression *expr, struct smatch_state *state)
 259 {
 260         struct relation *rel;
 261         struct smatch_state *estate;
 262
 263         estate = get_state_expr(SMATCH_EXTRA, expr);
 264
 265         if (!estate)
 266                 return;
 267
 268         FOR_EACH_PTR(get_dinfo(estate)->related, rel) {
 269                 set_state(id, rel->name, rel->sym, state);
 270         } END_FOR_EACH_PTR(rel);
 271 }