check_precedence.c

   1 /*
   2  * Copyright (C) 2010 Dan Carpenter.
   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
  20 static int my_id;
  21
  22 static int is_bool(struct expression *expr)
  23 {
  24         struct symbol *type;
  25
  26         type = get_type(expr);
  27         if (!type)
  28                 return 0;
  29         if (type_bits(type) == 1 && type->ctype.modifiers & MOD_UNSIGNED)
  30                 return 1;
  31         return 0;
  32 }
  33
  34 static int is_bool_from_context(struct expression *expr)
  35 {
  36         sval_t sval;
  37
  38         if (!get_implied_max(expr, &sval) || sval.uvalue > 1)
  39                 return 0;
  40         if (!get_implied_min(expr, &sval) || sval.value < 0)
  41                 return 0;
  42         return 1;
  43 }
  44
  45 static int is_bool_op(struct expression *expr)
  46 {
  47         expr = strip_expr(expr);
  48
  49         if (expr->type == EXPR_PREOP && expr->op == '!')
  50                 return 1;
  51         if (expr->type == EXPR_COMPARE)
  52                 return 1;
  53         if (expr->type == EXPR_LOGICAL)
  54                 return 1;
  55         return is_bool(expr);
  56 }
  57
  58 static void match_condition(struct expression *expr)
  59 {
  60         int print = 0;
  61
  62         if (expr->type == EXPR_COMPARE) {
  63                 if (expr->left->type == EXPR_COMPARE || expr->right->type == EXPR_COMPARE)
  64                         print = 1;
  65                 if (expr->left->type == EXPR_PREOP && expr->left->op == '!') {
  66                         if (expr->left->unop->type == EXPR_PREOP && expr->left->unop->op == '!')
  67                                 return;
  68                         if (expr->right->op == '!')
  69                                 return;
  70                         if (is_bool(expr->right))
  71                                 return;
  72                         if (is_bool(expr->left->unop))
  73                                 return;
  74                         if (is_bool_from_context(expr->left->unop))
  75                                 return;
  76                         print = 1;
  77                 }
  78         }
  79
  80         if (expr->type == EXPR_BINOP) {
  81                 if (expr->left->type == EXPR_COMPARE || expr->right->type == EXPR_COMPARE)
  82                         print = 1;
  83         }
  84
  85         if (print) {
  86                 sm_msg("warn: add some parenthesis here?");
  87                 return;
  88         }
  89
  90         if (expr->type == EXPR_BINOP && expr->op == '&') {
  91                 int i = 0;
  92
  93                 if (is_bool_op(expr->left))
  94                         i++;
  95                 if (is_bool_op(expr->right))
  96                         i++;
  97                 if (i == 1)
  98                         sm_msg("warn: maybe use && instead of &");
  99         }
 100 }
 101
 102 static void match_binop(struct expression *expr)
 103 {
 104         if (expr->op != '&')
 105                 return;
 106         if (expr->left->op == '!')
 107                 sm_msg("warn: add some parenthesis here?");
 108 }
 109
 110 static void match_mask(struct expression *expr)
 111 {
 112         if (expr->op != '&')
 113                 return;
 114         if (expr->right->type != EXPR_BINOP)
 115                 return;
 116         if (expr->right->op != SPECIAL_RIGHTSHIFT)
 117                 return;
 118
 119         sm_msg("warn: shift has higher precedence than mask");
 120 }
 121
 122 static void match_subtract_shift(struct expression *expr)
 123 {
 124         if (expr->op != SPECIAL_LEFTSHIFT)
 125                 return;
 126         if (expr->right->type != EXPR_BINOP)
 127                 return;
 128         if (expr->right->op != '-')
 129                 return;
 130         sm_msg("warn: subtract is higher precedence than shift");
 131 }
 132
 133 void check_precedence(int id)
 134 {
 135         my_id = id;
 136
 137         add_hook(&match_condition, CONDITION_HOOK);
 138         add_hook(&match_binop, BINOP_HOOK);
 139         add_hook(&match_mask, BINOP_HOOK);
 140         add_hook(&match_subtract_shift, BINOP_HOOK);
 141 }