check_or_vs_and.c

   1 /*
   2  * Copyright (C) 2012 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 #include "smatch.h"
  19 #include "smatch_function_hashtable.h"
  20
  21 static int my_id;
  22
  23 DEFINE_STRING_HASHTABLE_STATIC(unconstant_macros);
  24
  25 static int does_inc_dec(struct expression *expr)
  26 {
  27         if (expr->type == EXPR_PREOP || expr->type == EXPR_POSTOP) {
  28                 if (expr->op == SPECIAL_INCREMENT || expr->op == SPECIAL_DECREMENT)
  29                         return 1;
  30                 return does_inc_dec(expr->unop);
  31         }
  32         return 0;
  33 }
  34
  35 static int expr_equiv(struct expression *one, struct expression *two)
  36 {
  37         struct symbol *one_sym, *two_sym;
  38         char *one_name = NULL;
  39         char *two_name = NULL;
  40         int ret = 0;
  41
  42         if (does_inc_dec(one) || does_inc_dec(two))
  43                 return 0;
  44
  45         one_name = expr_to_str_sym(one, &one_sym);
  46         if (!one_name || !one_sym)
  47                 goto free;
  48         two_name = expr_to_str_sym(two, &two_sym);
  49         if (!two_name || !two_sym)
  50                 goto free;
  51         if (one_sym != two_sym)
  52                 goto free;
  53         if (strcmp(one_name, two_name) == 0)
  54                 ret = 1;
  55 free:
  56         free_string(one_name);
  57         free_string(two_name);
  58         return ret;
  59 }
  60
  61 static int inconsistent_check(struct expression *left, struct expression *right)
  62 {
  63         sval_t sval;
  64
  65         if (get_value(left->left, &sval)) {
  66                 if (get_value(right->left, &sval))
  67                         return expr_equiv(left->right, right->right);
  68                 if (get_value(right->right, &sval))
  69                         return expr_equiv(left->right, right->left);
  70                 return 0;
  71         }
  72         if (get_value(left->right, &sval)) {
  73                 if (get_value(right->left, &sval))
  74                         return expr_equiv(left->left, right->right);
  75                 if (get_value(right->right, &sval))
  76                         return expr_equiv(left->left, right->left);
  77                 return 0;
  78         }
  79
  80         return 0;
  81 }
  82
  83 static void check_or(struct expression *expr)
  84 {
  85         struct expression *left, *right;
  86
  87         left = strip_expr(expr->left);
  88         right = strip_expr(expr->right);
  89
  90         if (left->type != EXPR_COMPARE ||
  91                         left->op != SPECIAL_NOTEQUAL)
  92                 return;
  93         if (right->type != EXPR_COMPARE ||
  94                         right->op != SPECIAL_NOTEQUAL)
  95                 return;
  96         if (!inconsistent_check(left, right))
  97                 return;
  98
  99         sm_msg("warn: was && intended here instead of ||?");
 100 }
 101
 102 static void check_and(struct expression *expr)
 103 {
 104         struct expression *left, *right;
 105
 106         left = strip_expr(expr->left);
 107         right = strip_expr(expr->right);
 108
 109         if (left->type != EXPR_COMPARE ||
 110                         left->op != SPECIAL_EQUAL)
 111                 return;
 112         if (right->type != EXPR_COMPARE ||
 113                         right->op != SPECIAL_EQUAL)
 114                 return;
 115         if (!inconsistent_check(left, right))
 116                 return;
 117
 118         sm_msg("warn: was || intended here instead of &&?");
 119 }
 120
 121 static void match_logic(struct expression *expr)
 122 {
 123         if (expr->type != EXPR_LOGICAL)
 124                 return;
 125
 126         if (expr->op == SPECIAL_LOGICAL_OR)
 127                 check_or(expr);
 128         if (expr->op == SPECIAL_LOGICAL_AND)
 129                 check_and(expr);
 130 }
 131
 132 static int is_unconstant_macro(struct expression *expr)
 133 {
 134         char *macro;
 135
 136         macro = get_macro_name(expr->pos);
 137         if (!macro)
 138                 return 0;
 139         if (search_unconstant_macros(unconstant_macros, macro))
 140                 return 1;
 141         return 0;
 142 }
 143
 144 static void match_condition(struct expression *expr)
 145 {
 146         sval_t sval;
 147
 148         if (expr->type != EXPR_BINOP)
 149                 return;
 150         if (expr->op == '|') {
 151                 if (get_value(expr->left, &sval) || get_value(expr->right, &sval))
 152                         sm_msg("warn: suspicious bitop condition");
 153                 return;
 154         }
 155
 156         if (expr->op != '&')
 157                 return;
 158
 159         if (get_macro_name(expr->pos))
 160                 return;
 161         if (is_unconstant_macro(expr->left) || is_unconstant_macro(expr->right))
 162                 return;
 163
 164         if ((get_value(expr->left, &sval) && sval.value == 0) ||
 165             (get_value(expr->right, &sval) && sval.value == 0))
 166                 sm_msg("warn: bitwise AND condition is false here");
 167 }
 168
 169 static void match_binop(struct expression *expr)
 170 {
 171         sval_t left, right, sval;
 172
 173         if (expr->op != '&')
 174                 return;
 175         if (!get_value(expr, &sval) || sval.value != 0)
 176                 return;
 177         if (get_macro_name(expr->pos))
 178                 return;
 179         if (!get_value(expr->left, &left) || !get_value(expr->right, &right))
 180                 return;
 181         sm_msg("warn: odd binop '0x%llx & 0x%llx'", left.uvalue, right.uvalue);
 182 }
 183
 184 void check_or_vs_and(int id)
 185 {
 186         my_id = id;
 187
 188         unconstant_macros = create_function_hashtable(100);
 189         load_strings("unconstant_macros", unconstant_macros);
 190
 191         add_hook(&match_logic, LOGIC_HOOK);
 192         add_hook(&match_condition, CONDITION_HOOK);
 193         if (option_spammy)
 194                 add_hook(&match_binop, BINOP_HOOK);
 195 }