1 /*
2  * Copyright (C) 2011 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 #include "smatch_slist.h"
20 
21 static int my_id;
22 
right_side_changes(struct expression * expr)23 static int right_side_changes(struct expression *expr)
24 {
25 	sval_t dummy;
26 
27 	if (get_value(expr->right, &dummy))
28 		return 0;
29 	return 1;
30 }
31 
get_iterator_set(struct statement * stmt)32 static struct expression *get_iterator_set(struct statement *stmt)
33 {
34 	struct expression *expr;
35 
36 	if (!stmt)
37 		return NULL;
38 	if (stmt->type != STMT_EXPRESSION)
39 		return NULL;
40 	expr = stmt->expression;
41 	if (expr->type != EXPR_ASSIGNMENT)
42 		return NULL;
43 	if (expr->op != '=')
44 		return NULL;
45 	if (right_side_changes(expr))
46 		return NULL;
47 	return expr->left;
48 }
49 
get_iterator_tested(struct expression * expr)50 static struct expression *get_iterator_tested(struct expression *expr)
51 {
52 	if (!expr)
53 		return NULL;
54 	if (expr->type != EXPR_COMPARE)
55 		return NULL;
56 	return expr->left;
57 }
58 
match_loop(struct statement * stmt)59 static void match_loop(struct statement *stmt)
60 {
61 	struct expression *iterator;
62 	char *iter_set;
63 	char *iter_tested;
64 
65 	if (get_macro_name(stmt->pos))
66 		return;
67 
68 	iterator = get_iterator_set(stmt->iterator_pre_statement);
69 	iter_set = expr_to_var(iterator);
70 	iterator = get_iterator_tested(stmt->iterator_pre_condition);
71 	iter_tested = expr_to_var(iterator);
72 	if (!iter_set || !iter_tested)
73 		goto free;
74 	if (strcmp(iter_set, iter_tested))
75 		goto free;
76 
77 	/* smatch doesn't handle loops correctly so this silences some
78 	 * false positives.
79 	 */
80 	if (right_side_changes(stmt->iterator_pre_condition))
81 		goto free;
82 
83 	if (implied_condition_false(stmt->iterator_pre_condition))
84 		sm_warning("we never enter this loop");
85 
86 free:
87 	free_string(iter_set);
88 	free_string(iter_tested);
89 }
90 
check_bogus_loop(int id)91 void check_bogus_loop(int id)
92 {
93 	my_id = id;
94 	add_hook(&match_loop, PRELOOP_HOOK);
95 }
96