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_no_inc_dec(struct expression *one, struct expression *two)
  36 {
  37         if (does_inc_dec(one) || does_inc_dec(two))
  38                 return 0;
  39         return expr_equiv(one, two);
  40 }
  41
  42 static int inconsistent_check(struct expression *left, struct expression *right)
  43 {
  44         sval_t sval;
  45
  46         if (get_value(left->left, &sval)) {
  47                 if (get_value(right->left, &sval))
  48                         return expr_equiv_no_inc_dec(left->right, right->right);
  49                 if (get_value(right->right, &sval))
  50                         return expr_equiv_no_inc_dec(left->right, right->left);
  51                 return 0;
  52         }
  53         if (get_value(left->right, &sval)) {
  54                 if (get_value(right->left, &sval))
  55                         return expr_equiv_no_inc_dec(left->left, right->right);
  56                 if (get_value(right->right, &sval))
  57                         return expr_equiv_no_inc_dec(left->left, right->left);
  58                 return 0;
  59         }
  60
  61         return 0;
  62 }
  63
  64 static void check_or(struct expression *expr)
  65 {
  66         struct expression *left, *right;
  67
  68         left = strip_expr(expr->left);
  69         right = strip_expr(expr->right);
  70
  71         if (left->type != EXPR_COMPARE ||
  72                         left->op != SPECIAL_NOTEQUAL)
  73                 return;
  74         if (right->type != EXPR_COMPARE ||
  75                         right->op != SPECIAL_NOTEQUAL)
  76                 return;
  77         if (!inconsistent_check(left, right))
  78                 return;
  79
  80         sm_msg("warn: was && intended here instead of ||?");
  81 }
  82
  83 static void check_and(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_EQUAL)
  92                 return;
  93         if (right->type != EXPR_COMPARE ||
  94                         right->op != SPECIAL_EQUAL)
  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 match_logic(struct expression *expr)
 103 {
 104         if (expr->type != EXPR_LOGICAL)
 105                 return;
 106
 107         if (expr->op == SPECIAL_LOGICAL_OR)
 108                 check_or(expr);
 109         if (expr->op == SPECIAL_LOGICAL_AND)
 110                 check_and(expr);
 111 }
 112
 113 static int is_unconstant_macro(struct expression *expr)
 114 {
 115         char *macro;
 116
 117         macro = get_macro_name(expr->pos);
 118         if (!macro)
 119                 return 0;
 120         if (search_unconstant_macros(unconstant_macros, macro))
 121                 return 1;
 122         return 0;
 123 }
 124
 125 static void match_condition(struct expression *expr)
 126 {
 127         sval_t sval;
 128
 129         if (expr->type != EXPR_BINOP)
 130                 return;
 131         if (expr->op == '|') {
 132                 if (get_value(expr->left, &sval) || get_value(expr->right, &sval))
 133                         sm_msg("warn: suspicious bitop condition");
 134                 return;
 135         }
 136
 137         if (expr->op != '&')
 138                 return;
 139
 140         if (get_macro_name(expr->pos))
 141                 return;
 142         if (is_unconstant_macro(expr->left) || is_unconstant_macro(expr->right))
 143                 return;
 144
 145         if ((get_value(expr->left, &sval) && sval.value == 0) ||
 146             (get_value(expr->right, &sval) && sval.value == 0))
 147                 sm_msg("warn: bitwise AND condition is false here");
 148 }
 149
 150 static void match_binop(struct expression *expr)
 151 {
 152         sval_t left, right, sval;
 153
 154         if (expr->op != '&')
 155                 return;
 156         if (!get_value(expr, &sval) || sval.value != 0)
 157                 return;
 158         if (get_macro_name(expr->pos))
 159                 return;
 160         if (!get_value(expr->left, &left) || !get_value(expr->right, &right))
 161                 return;
 162         sm_msg("warn: odd binop '0x%llx & 0x%llx'", left.uvalue, right.uvalue);
 163 }
 164
 165 void check_or_vs_and(int id)
 166 {
 167         my_id = id;
 168
 169         unconstant_macros = create_function_hashtable(100);
 170         load_strings("unconstant_macros", unconstant_macros);
 171
 172         add_hook(&match_logic, LOGIC_HOOK);
 173         add_hook(&match_condition, CONDITION_HOOK);
 174         if (option_spammy)
 175                 add_hook(&match_binop, BINOP_HOOK);
 176 }