check_double_checking.c

   1 /*
   2  * Copyright (C) 2014 Oracle.
   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 #define _GNU_SOURCE
  19 #include <string.h>
  20 #include "smatch.h"
  21 #include "smatch_extra.h"
  22
  23 static int my_id;
  24
  25 static bool in_same_block(struct expression *one, struct expression *two)
  26 {
  27         struct statement *a, *b;
  28
  29         a = get_parent_stmt(one);
  30         b = get_parent_stmt(two);
  31         if (!a || !b)
  32                 return false;
  33         return a->parent == b->parent;
  34 }
  35
  36 static bool is_loop_condition(struct expression *expr)
  37 {
  38         struct statement *stmt;
  39
  40         /*
  41          * Two things.  First of all get_stored_condition() is buggy.
  42          * Secondly, even if it were not buggy there would be an
  43          * issue checking the pre condition before the loop runs.
  44          */
  45         stmt = get_parent_stmt(expr);
  46         if (stmt && stmt->type == STMT_ITERATOR)
  47                 return true;
  48         return false;
  49 }
  50
  51 static bool is_part_of_logical(struct expression *expr)
  52 {
  53         while ((expr = expr_get_parent_expr(expr))) {
  54                 if (expr->type == EXPR_PREOP) {
  55                     if (expr->op == '!' ||
  56                         expr->op == '(')
  57                         continue;
  58                 }
  59                 if (expr->type == EXPR_COMPARE)
  60                         continue;
  61                 if (expr->type == EXPR_LOGICAL)
  62                         return true;
  63                 return false;
  64         }
  65         return false;
  66 }
  67
  68 static bool last_in_chain_of_else_if_statements(struct expression *expr)
  69 {
  70         struct statement *stmt;
  71
  72         stmt = get_parent_stmt(expr);
  73         if (!stmt)
  74                 return false;
  75         if (stmt->type != STMT_IF)
  76                 return false;
  77         if (stmt->if_false)
  78                 return false;
  79         stmt = stmt_get_parent_stmt(stmt);
  80         if (!stmt)
  81                 return false;
  82         if (stmt->type != STMT_IF)
  83                 return false;
  84         return true;
  85 }
  86
  87 static bool is_global(struct expression *expr)
  88 {
  89         struct symbol *sym;
  90
  91         sym = expr_to_sym(expr);
  92         if (!sym)
  93                 return false;
  94         return !!(sym->ctype.modifiers & MOD_TOPLEVEL);
  95 }
  96
  97 static bool is_dereference(struct expression *expr)
  98 {
  99         expr = strip_expr(expr);
 100
 101         if (expr->type == EXPR_COMPARE ||
 102             expr->type == EXPR_BINOP) {
 103                 if (is_dereference(expr->left) ||
 104                     is_dereference(expr->right))
 105                         return true;
 106                 return false;
 107         }
 108         if (expr->type != EXPR_DEREF)
 109                 return false;
 110         return true;
 111 }
 112
 113 static void match_condition(struct expression *expr)
 114 {
 115         struct expression *old_condition;
 116         struct smatch_state *state;
 117         struct symbol *sym;
 118         char *name;
 119
 120         if (__in_fake_parameter_assign || __reparsing_code)
 121                 return;
 122
 123         if (get_macro_name(expr->pos))
 124                 return;
 125
 126         if (is_loop_condition(expr))
 127                 return;
 128
 129         if (is_part_of_logical(expr))
 130                 return;
 131
 132         if (last_in_chain_of_else_if_statements(expr))
 133                 return;
 134
 135         if (is_global(expr))
 136                 return;
 137
 138         if (is_dereference(expr))
 139                 return;
 140
 141         state = get_stored_condition(expr);
 142         if (!state || !state->data)
 143                 return;
 144         old_condition = state->data;
 145         if (get_macro_name(old_condition->pos))
 146                 return;
 147
 148         if (inside_loop() && !in_same_block(old_condition, expr))
 149                 return;
 150
 151         name = expr_to_str_sym(expr, &sym);
 152         state = get_state(my_id, name, sym);
 153         if (state != &true_state && state != &false_state)
 154                 goto free;
 155
 156         sm_warning("duplicate check '%s' (previous on line %d)", name, old_condition->pos.line);
 157 free:
 158         free_string(name);
 159 }
 160
 161 static bool has_array(struct expression *expr)
 162 {
 163         if (!expr)
 164                 return false;
 165
 166         if (is_array(expr))
 167                 return true;
 168         if (expr->type == EXPR_COMPARE)
 169                 return is_array(expr->left);
 170         return false;
 171 }
 172
 173 static void match_condition_store(struct expression *expr)
 174 {
 175         struct symbol *sym;
 176         sval_t dummy;
 177         char *name;
 178
 179         if (get_value(expr, &dummy))
 180                 return;
 181
 182         if (has_array(expr))
 183                 return;
 184
 185         name = expr_to_str_sym(expr, &sym);
 186         if (!name)
 187                 return;
 188
 189         if (sym && sym->ctype.modifiers & MOD_TOPLEVEL)
 190                 goto free;
 191
 192         set_true_false_states(my_id, name, sym, &true_state, &false_state);
 193 free:
 194         free_string(name);
 195 }
 196
 197 void check_double_checking(int id)
 198 {
 199         my_id = id;
 200
 201         if (!option_spammy)
 202                 return;
 203
 204         turn_off_implications(my_id);
 205
 206         add_hook(&match_condition, CONDITION_HOOK);
 207         add_hook(&match_condition_store, CONDITION_HOOK);
 208 }