check_bogus_loop.c

   1 /*
   2  * smatch/check_bogus_for_loop.c
   3  *
   4  * Copyright (C) 2011 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include "smatch.h"
  11 #include "smatch_slist.h"
  12
  13 static int my_id;
  14
  15 static int right_side_changes(struct expression *expr)
  16 {
  17         sval_t dummy;
  18
  19         if (get_value(expr->right, &dummy))
  20                 return 0;
  21         return 1;
  22 }
  23
  24 static struct expression *get_iterator_set(struct statement *stmt)
  25 {
  26         struct expression *expr;
  27
  28         if (!stmt)
  29                 return NULL;
  30         if (stmt->type != STMT_EXPRESSION)
  31                 return NULL;
  32         expr = stmt->expression;
  33         if (expr->type != EXPR_ASSIGNMENT)
  34                 return NULL;
  35         if (expr->op != '=')
  36                 return NULL;
  37         if (right_side_changes(expr))
  38                 return NULL;
  39         return expr->left;
  40 }
  41
  42 static struct expression *get_iterator_tested(struct expression *expr)
  43 {
  44         if (!expr)
  45                 return NULL;
  46         if (expr->type != EXPR_COMPARE)
  47                 return NULL;
  48         return expr->left;
  49 }
  50
  51 static void match_loop(struct statement *stmt)
  52 {
  53         struct expression *iterator;
  54         char *iter_set;
  55         char *iter_tested;
  56
  57         if (get_macro_name(stmt->pos))
  58                 return;
  59
  60         iterator = get_iterator_set(stmt->iterator_pre_statement);
  61         iter_set = get_variable_from_expr(iterator, NULL);
  62         iterator = get_iterator_tested(stmt->iterator_pre_condition);
  63         iter_tested = get_variable_from_expr(iterator, NULL);
  64         if (!iter_set || !iter_tested)
  65                 goto free;
  66         if (strcmp(iter_set, iter_tested))
  67                 goto free;
  68
  69         /* smatch doesn't handle loops correctly so this silences some
  70          * false positives.
  71          */
  72         if (right_side_changes(stmt->iterator_pre_condition))
  73                 goto free;
  74
  75         if (implied_condition_false(stmt->iterator_pre_condition))
  76                 sm_msg("warn: we never enter this loop");
  77
  78 free:
  79         free_string(iter_set);
  80         free_string(iter_tested);
  81 }
  82
  83 void check_bogus_loop(int id)
  84 {
  85         my_id = id;
  86         add_hook(&match_loop, PRELOOP_HOOK);
  87 }