1 /* Create a pipe, with specific opening flags.
2    Copyright (C) 2009-2021 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 Lesser General Public License as published by
6    the Free Software Foundation; either version 2, or (at your option)
7    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 Lesser General Public License for more details.
13 
14    You should have received a copy of the GNU Lesser General Public License along
15    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
pipe2(int fd[2],int flags)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 }
168