check_deref_check.c

   1 /*
   2  * sparse/check_deref_check.c
   3  *
   4  * Copyright (C) 2009 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include "smatch.h"
  11 #include "smatch_extra.h"
  12
  13 extern struct expression_list *big_expression_stack;
  14
  15 static int my_id;
  16
  17 STATE(derefed);
  18 STATE(oktocheck);
  19
  20 static void underef(const char *name, struct symbol *sym, struct expression *expr, void *unused)
  21 {
  22         set_state(my_id, name, sym, &oktocheck);
  23 }
  24
  25 static int is_not_really_dereference()
  26 {
  27         struct expression *tmp;
  28         int i = 0;
  29         int dot_ops = 0;
  30
  31         FOR_EACH_PTR_REVERSE(big_expression_stack, tmp) {
  32                 if (!i++)
  33                         continue;
  34                 if (tmp->op == '(')
  35                         continue;
  36                 if (tmp->op == '.' && !dot_ops++)
  37                         continue;
  38                 if (tmp->op == '&')
  39                         return 1;
  40                 return 0;
  41         } END_FOR_EACH_PTR_REVERSE(tmp);
  42         return 0;
  43 }
  44
  45 static void match_dereference(struct expression *expr)
  46 {
  47         char *name;
  48
  49         if (expr->type != EXPR_PREOP)
  50                 return;
  51         if (is_not_really_dereference())
  52                 return;
  53
  54         expr = strip_expr(expr->unop);
  55         if (implied_not_equal(expr, 0))
  56                 return;
  57         set_state_expr(my_id, expr, &derefed);
  58         name = get_variable_from_expr(expr, NULL);
  59         if (!name)
  60                 return;
  61         add_modification_hook(name, &underef, NULL);
  62         free_string(name);
  63 }
  64
  65 static void match_condition(struct expression *expr)
  66 {
  67         if (get_state_expr(my_id, expr) == &derefed) {
  68                 char *name;
  69
  70                 name = get_variable_from_expr(expr, NULL);
  71                 if (!implied_not_equal(expr, 0))
  72                         sm_msg("warn: variable dereferenced before check '%s'", name);
  73                 set_state_expr(my_id, expr, &oktocheck);
  74                 free_string(name);
  75         }
  76 }
  77
  78 void check_deref_check(int id)
  79 {
  80         my_id = id;
  81         set_default_state(my_id, &oktocheck);
  82         add_hook(&match_dereference, DEREF_HOOK);
  83         add_hook(&match_condition, CONDITION_HOOK);
  84 }