1 /* Open a stream to a file.
2 Copyright (C) 2007-2021 Free Software Foundation, Inc.
3
4 This program is free software: you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 3 of the License, or
7 (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 <https://www.gnu.org/licenses/>. */
16
17 /* Written by Bruno Haible <bruno@clisp.org>, 2007. */
18
19 /* If the user's config.h happens to include <stdio.h>, let it include only
20 the system's <stdio.h> here, so that orig_freopen doesn't recurse to
21 rpl_freopen. */
22 #define _GL_ALREADY_INCLUDING_STDIO_H
23 #include <config.h>
24
25 /* Get the original definition of freopen. It might be defined as a macro. */
26 #include <stdio.h>
27 #undef _GL_ALREADY_INCLUDING_STDIO_H
28
29 #include <errno.h>
30
31 static FILE *
orig_freopen(const char * filename,const char * mode,FILE * stream)32 orig_freopen (const char *filename, const char *mode, FILE *stream)
33 {
34 return freopen (filename, mode, stream);
35 }
36
37 /* Specification. */
38 /* Write "stdio.h" here, not <stdio.h>, otherwise OSF/1 5.1 DTK cc eliminates
39 this include because of the preliminary #include <stdio.h> above. */
40 #include "stdio.h"
41
42 #include <fcntl.h>
43 #include <string.h>
44 #include <unistd.h>
45
46 FILE *
rpl_freopen(const char * filename,const char * mode,FILE * stream)47 rpl_freopen (const char *filename, const char *mode, FILE *stream)
48 {
49 FILE *result;
50 #if defined _WIN32 && ! defined __CYGWIN__
51 char const *null_device = "NUL";
52 if (filename && strcmp (filename, "/dev/null") == 0)
53 filename = null_device;
54 #else
55 char const *null_device = "/dev/null";
56 #endif
57
58 #ifdef __KLIBC__
59 errno = 0;
60 #endif
61
62 result = orig_freopen (filename, mode, stream);
63
64 if (!result)
65 {
66 #ifdef __KLIBC__
67 /* On OS/2 kLIBC, freopen returns NULL even if it is successful
68 if filename is NULL. */
69 if (!filename && !errno)
70 result = stream;
71 #endif
72 }
73 else if (filename)
74 {
75 int fd = fileno (result);
76 if (dup2 (fd, fd) < 0 && errno == EBADF)
77 {
78 int nullfd = open (null_device, O_RDONLY | O_CLOEXEC);
79 int err = 0;
80 if (nullfd != fd)
81 {
82 if (dup2 (nullfd, fd) < 0)
83 err = 1;
84 close (nullfd);
85 }
86 if (!err)
87 result = orig_freopen (filename, mode, result);
88 }
89 }
90
91 return result;
92 }
93