1/* Checking strncat.
2 Copyright (C) 1991-2017 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11In addition to the permissions in the GNU General Public License, the
12Free Software Foundation gives you unlimited permission to link the
13compiled version of this file into combinations with other programs,
14and to distribute those combinations without any restriction coming
15from the use of this file. (The General Public License restrictions
16do apply in other respects; for example, they cover modification of
17the file, and distribution when not linked into a combine
18executable.)
19
20GCC is distributed in the hope that it will be useful, but WITHOUT ANY
21WARRANTY; without even the implied warranty of MERCHANTABILITY or
22FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
23for more details.
24
25Under Section 7 of GPL version 3, you are granted additional
26permissions described in the GCC Runtime Library Exception, version
273.1, as published by the Free Software Foundation.
28
29You should have received a copy of the GNU General Public License and
30a copy of the GCC Runtime Library Exception along with this program;
31see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
32<http://www.gnu.org/licenses/>. */
33
34
35#include "config.h"
36#include <ssp/ssp.h>
37#ifdef HAVE_STRING_H
38# include <string.h>
39#endif
40
41extern void __chk_fail (void) __attribute__((__noreturn__));
42
43char *
44__strncat_chk (char *__restrict__ dest, const char *__restrict__ src,
45 size_t n, size_t slen)
46{
47 char c;
48 char *s = dest;
49
50 do
51 {
52 if (slen-- == 0)
53 __chk_fail ();
54 c = *dest++;
55 }
56 while (c != '\0');
57
58 ++slen;
59 dest -= 2;
60
61 if (n >= 4)
62 {
63 size_t n4 = n >> 2;
64 do
65 {
66 if (slen-- == 0)
67 __chk_fail ();
68 c = *src++;
69 *++dest = c;
70 if (c == '\0')
71 return s;
72 if (slen-- == 0)
73 __chk_fail ();
74 c = *src++;
75 *++dest = c;
76 if (c == '\0')
77 return s;
78 if (slen-- == 0)
79 __chk_fail ();
80 c = *src++;
81 *++dest = c;
82 if (c == '\0')
83 return s;
84 if (slen-- == 0)
85 __chk_fail ();
86 c = *src++;
87 *++dest = c;
88 if (c == '\0')
89 return s;
90 } while (--n4 > 0);
91 n &= 3;
92 }
93
94 while (n > 0)
95 {
96 if (slen-- == 0)
97 __chk_fail ();
98 c = *src++;
99 *++dest = c;
100 if (c == '\0')
101 return s;
102 n--;
103 }
104
105 if (c != '\0')
106 {
107 if (slen-- == 0)
108 __chk_fail ();
109 *++dest = '\0';
110 }
111
112 return s;
113}
114