1 /* Create a pipe, with specific opening flags.
2 Copyright (C) 2009-2021 Free Software Foundation, Inc.
3
4 This file is free software: you can redistribute it and/or modify
5 it under the terms of the GNU Lesser General Public License as
6 published by the Free Software Foundation; either version 2.1 of the
7 License, or (at your option) any later version.
8
9 This file 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 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public License
15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
16
17 #include <config.h>
18
19 /* Specification. */
20 #include <unistd.h>
21
22 #include <errno.h>
23 #include <fcntl.h>
24
25 #include "binary-io.h"
26 #include "verify.h"
27
28 #if GNULIB_defined_O_NONBLOCK
29 # include "nonblocking.h"
30 #endif
31
32 #if defined _WIN32 && ! defined __CYGWIN__
33 /* Native Windows API. */
34
35 # include <io.h>
36
37 #endif
38
39 int
40 pipe2 (int fd[2], int flags)
41 {
42 /* Mingw _pipe() corrupts fd on failure; also, if we succeed at
43 creating the pipe but later fail at changing fcntl, we want
44 to leave fd unchanged: http://austingroupbugs.net/view.php?id=467 */
45 int tmp[2];
46 tmp[0] = fd[0];
47 tmp[1] = fd[1];
48
49 #if HAVE_PIPE2
50 # undef pipe2
51 /* Try the system call first, if it exists. (We may be running with a glibc
52 that has the function but with an older kernel that lacks it.) */
53 {
54 /* Cache the information whether the system call really exists. */
55 static int have_pipe2_really; /* 0 = unknown, 1 = yes, -1 = no */
56 if (have_pipe2_really >= 0)
57 {
58 int result = pipe2 (fd, flags);
59 if (!(result < 0 && errno == ENOSYS))
60 {
61 have_pipe2_really = 1;
62 return result;
63 }
64 have_pipe2_really = -1;
65 }
66 }
67 #endif
68
69 /* Check the supported flags. */
70 if ((flags & ~(O_CLOEXEC | O_NONBLOCK | O_BINARY | O_TEXT)) != 0)
71 {
72 errno = EINVAL;
73 return -1;
74 }
75
76 #if defined _WIN32 && ! defined __CYGWIN__
77 /* Native Windows API. */
78
79 if (_pipe (fd, 4096, flags & ~O_NONBLOCK) < 0)
80 {
81 fd[0] = tmp[0];
82 fd[1] = tmp[1];
83 return -1;
84 }
85
86 /* O_NONBLOCK handling.
87 On native Windows platforms, O_NONBLOCK is defined by gnulib. Use the
88 functions defined by the gnulib module 'nonblocking'. */
89 # if GNULIB_defined_O_NONBLOCK
90 if (flags & O_NONBLOCK)
91 {
92 if (set_nonblocking_flag (fd[0], true) != 0
93 || set_nonblocking_flag (fd[1], true) != 0)
94 goto fail;
95 }
96 # else
97 {
98 verify (O_NONBLOCK == 0);
99 }
100 # endif
101
102 return 0;
103
104 #else
105 /* Unix API. */
106
107 if (pipe (fd) < 0)
108 return -1;
109
110 /* POSIX <https://pubs.opengroup.org/onlinepubs/9699919799/functions/pipe.html>
111 says that initially, the O_NONBLOCK and FD_CLOEXEC flags are cleared on
112 both fd[0] and fd[1]. */
113
114 /* O_NONBLOCK handling.
115 On Unix platforms, O_NONBLOCK is defined by the system. Use fcntl(). */
116 if (flags & O_NONBLOCK)
117 {
118 int fcntl_flags;
119
120 if ((fcntl_flags = fcntl (fd[1], F_GETFL, 0)) < 0
121 || fcntl (fd[1], F_SETFL, fcntl_flags | O_NONBLOCK) == -1
122 || (fcntl_flags = fcntl (fd[0], F_GETFL, 0)) < 0
123 || fcntl (fd[0], F_SETFL, fcntl_flags | O_NONBLOCK) == -1)
124 goto fail;
125 }
126
127 if (flags & O_CLOEXEC)
128 {
129 int fcntl_flags;
130
131 if ((fcntl_flags = fcntl (fd[1], F_GETFD, 0)) < 0
132 || fcntl (fd[1], F_SETFD, fcntl_flags | FD_CLOEXEC) == -1
133 || (fcntl_flags = fcntl (fd[0], F_GETFD, 0)) < 0
134 || fcntl (fd[0], F_SETFD, fcntl_flags | FD_CLOEXEC) == -1)
135 goto fail;
136 }
137
138 # if O_BINARY
139 if (flags & O_BINARY)
140 {
141 set_binary_mode (fd[1], O_BINARY);
142 set_binary_mode (fd[0], O_BINARY);
143 }
144 else if (flags & O_TEXT)
145 {
146 set_binary_mode (fd[1], O_TEXT);
147 set_binary_mode (fd[0], O_TEXT);
148 }
149 # endif
150
151 return 0;
152
153 #endif
154
155 #if GNULIB_defined_O_NONBLOCK || !(defined _WIN32 && ! defined __CYGWIN__)
156 fail:
157 {
158 int saved_errno = errno;
159 close (fd[0]);
160 close (fd[1]);
161 fd[0] = tmp[0];
162 fd[1] = tmp[1];
163 errno = saved_errno;
164 return -1;
165 }
166 #endif
167 }