check_deref_check.c

   1 /*
   2  * Copyright (C) 2009 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 "smatch.h"
  19 #include "smatch_extra.h"
  20
  21 static int my_id;
  22
  23 STATE(derefed);
  24
  25 static void underef(struct sm_state *sm, struct expression *mod_expr)
  26 {
  27         set_state(my_id, sm->name, sm->sym, &undefined);
  28 }
  29
  30 static void match_dereference(struct expression *expr)
  31 {
  32         if (__in_fake_assign)
  33                 return;
  34
  35         if (expr->type != EXPR_PREOP)
  36                 return;
  37         expr = strip_expr(expr->unop);
  38         if (!is_pointer(expr))
  39                 return;
  40         if (implied_not_equal(expr, 0))
  41                 return;
  42
  43         if (is_impossible_path())
  44                 return;
  45
  46         set_state_expr(my_id, expr, &derefed);
  47 }
  48
  49 static void set_param_dereferenced(struct expression *call, struct expression *arg, char *key, char *unused)
  50 {
  51         struct symbol *sym;
  52         char *name;
  53
  54         name = get_variable_from_key(arg, key, &sym);
  55         if (!name || !sym)
  56                 goto free;
  57
  58         if (implied_not_equal_name_sym(name, sym, 0))
  59                 goto free;
  60         set_state(my_id, name, sym, &derefed);
  61
  62 free:
  63         free_string(name);
  64 }
  65
  66 static void match_condition(struct expression *expr)
  67 {
  68         struct sm_state *sm;
  69
  70         if (__in_pre_condition)
  71                 return;
  72
  73         if (get_macro_name(expr->pos))
  74                 return;
  75
  76         if (!is_pointer(expr))
  77                 return;
  78
  79         sm = get_sm_state_expr(my_id, expr);
  80         if (!sm || sm->state != &derefed)
  81                 return;
  82
  83         sm_warning("variable dereferenced before check '%s' (see line %d)", sm->name, sm->line);
  84         set_state_expr(my_id, expr, &undefined);
  85 }
  86
  87 void check_deref_check(int id)
  88 {
  89         my_id = id;
  90         add_hook(&match_dereference, DEREF_HOOK);
  91         add_hook(&match_condition, CONDITION_HOOK);
  92         select_return_implies_hook(DEREFERENCE, &set_param_dereferenced);
  93         add_modification_hook(my_id, &underef);
  94 }