1/* Checking strncat.
2   Copyright (C) 1991, 1997, 2003, 2004, 2005 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 2, 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
25You should have received a copy of the GNU General Public License
26along with GCC; see the file COPYING.  If not, write to the Free
27Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
2802110-1301, USA.  */
29
30/* As a special exception, if you link this library with files compiled with
31   GCC to produce an executable, this does not cause the resulting executable
32   to be covered by the GNU General Public License. This exception does not
33   however invalidate any other reasons why the executable file might be
34   covered by the GNU General Public License.  */
35
36#include "config.h"
37#include <ssp/ssp.h>
38#ifdef HAVE_STRING_H
39# include <string.h>
40#endif
41
42extern void __chk_fail (void) __attribute__((__noreturn__));
43
44char *
45__strncat_chk (char *__restrict__ dest, const char *__restrict__ src,
46               size_t n, size_t slen)
47{
48  char c;
49  char *s = dest;
50
51  do
52    {
53      if (slen-- == 0)
54        __chk_fail ();
55      c = *dest++;
56    }
57  while (c != '\0');
58
59  ++slen;
60  dest -= 2;
61
62  if (n >= 4)
63    {
64      size_t n4 = n >> 2;
65      do
66        {
67          if (slen-- == 0)
68            __chk_fail ();
69          c = *src++;
70          *++dest = c;
71          if (c == '\0')
72            return s;
73          if (slen-- == 0)
74            __chk_fail ();
75          c = *src++;
76          *++dest = c;
77          if (c == '\0')
78            return s;
79          if (slen-- == 0)
80            __chk_fail ();
81          c = *src++;
82          *++dest = c;
83          if (c == '\0')
84            return s;
85          if (slen-- == 0)
86            __chk_fail ();
87          c = *src++;
88          *++dest = c;
89          if (c == '\0')
90            return s;
91          if (slen-- == 0)
92            __chk_fail ();
93          c = *src++;
94          *++dest = c;
95          if (c == '\0')
96            return s;
97        } while (--n4 > 0);
98      n &= 3;
99    }
100
101  while (n > 0)
102    {
103      if (slen-- == 0)
104        __chk_fail ();
105      c = *src++;
106      *++dest = c;
107      if (c == '\0')
108        return s;
109      n--;
110    }
111
112  if (c != '\0')
113    {
114      if (slen-- == 0)
115        __chk_fail ();
116      *++dest = '\0';
117    }
118
119  return s;
120}
121