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#include "smatch.h"
19#include "smatch_extra.h"
20
21static int my_id;
22static int my_return_id;
23
24STATE(impossible);
25
26int is_impossible_path(void)
27{
28	if (get_state(my_id, "impossible", NULL) == &impossible)
29		return 1;
30	return 0;
31}
32
33static void handle_compare(struct expression *left, int op, struct expression *right)
34{
35	int true_impossible = 0;
36	int false_impossible = 0;
37
38	left = strip_expr(left);
39	while (left && left->type == EXPR_ASSIGNMENT)
40		left = strip_expr(left->left);
41
42	if (!possibly_true(left, op, right))
43		true_impossible = 1;
44	if (!possibly_false(left, op, right))
45		false_impossible = 1;
46
47	if (!true_impossible && !false_impossible)
48		return;
49
50	set_true_false_states(my_id, "impossible", NULL,
51			      true_impossible ? &impossible : NULL,
52			      false_impossible ? &impossible : NULL);
53
54	if (inside_loop())
55		return;
56
57	set_true_false_states(my_return_id, "impossible", NULL,
58			      true_impossible ? &impossible : NULL,
59			      false_impossible ? &impossible : NULL);
60}
61
62static void match_condition(struct expression *expr)
63{
64	if (expr->type == EXPR_COMPARE)
65		handle_compare(expr->left, expr->op, expr->right);
66	else
67		handle_compare(expr, SPECIAL_NOTEQUAL, zero_expr());
68}
69
70void set_path_impossible(void)
71{
72	set_state(my_id, "impossible", NULL, &impossible);
73
74	if (inside_loop())
75		return;
76
77	set_state(my_return_id, "impossible", NULL, &impossible);
78}
79
80static void match_case(struct expression *expr, struct range_list *rl)
81{
82	if (rl)
83		return;
84	set_path_impossible();
85}
86
87static void print_impossible_return(int return_id, char *return_ranges, struct expression *expr)
88{
89	if (get_state(my_return_id, "impossible", NULL) == &impossible) {
90		if (option_debug)
91			sm_msg("impossible return.  return_id = %d return ranges = %s", return_id, return_ranges);
92		sql_insert_return_states(return_id, return_ranges, CULL_PATH, -1, "", "");
93	}
94}
95
96void register_impossible(int id)
97{
98	my_id = id;
99
100	add_hook(&match_condition, CONDITION_HOOK);
101	add_hook(&match_case, CASE_HOOK);
102}
103
104void register_impossible_return(int id)
105{
106	my_return_id = id;
107
108	add_split_return_callback(&print_impossible_return);
109}
110