1 /* Close standard output and standard error, exiting with a diagnostic on error.
2
3 Copyright (C) 1998-2002, 2004, 2006, 2008-2023 Free Software Foundation,
4 Inc.
5
6 This program is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
10
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <https://www.gnu.org/licenses/>. */
18
19 #include <config.h>
20
21 #include "closeout.h"
22
23 #include <errno.h>
24 #include <stdio.h>
25 #include <unistd.h>
26
27 #include "gettext.h"
28 #define _(msgid) gettext (msgid)
29
30 #include "close-stream.h"
31 #include "error.h"
32 #include "exitfail.h"
33 #include "quotearg.h"
34
35 #ifndef __has_feature
36 # define __has_feature(a) false
37 #endif
38
39 #if defined __SANITIZE_ADDRESS__ || __has_feature (address_sanitizer)
40 enum { SANITIZE_ADDRESS = true };
41 #else
42 enum { SANITIZE_ADDRESS = false };
43 #endif
44
45 static const char *file_name;
46
47 /* Set the file name to be reported in the event an error is detected
48 by close_stdout. */
49 void
50 close_stdout_set_file_name (const char *file)
51 {
52 file_name = file;
53 }
54
55 static bool ignore_EPIPE /* = false */;
56
57 /* Specify the reaction to an EPIPE error during the closing of stdout:
58 - If ignore = true, it shall be ignored.
59 - If ignore = false, it shall evoke a diagnostic, along with a nonzero
60 exit status.
61 The default is ignore = false.
62
63 This setting matters only if the SIGPIPE signal is ignored (i.e. its
64 handler set to SIG_IGN) or blocked. Only particular programs need to
65 temporarily ignore SIGPIPE. If SIGPIPE is ignored or blocked because
66 it was ignored or blocked in the parent process when it created the
67 child process, it usually is a bug in the parent process: It is bad
68 practice to have SIGPIPE ignored or blocked while creating a child
69 process.
70
71 EPIPE occurs when writing to a pipe or socket that has no readers now,
72 when SIGPIPE is ignored or blocked.
73
74 The ignore = false setting is suitable for a scenario where it is normally
75 guaranteed that the pipe writer terminates before the pipe reader. In
76 this case, an EPIPE is an indication of a premature termination of the
77 pipe reader and should lead to a diagnostic and a nonzero exit status.
78
79 The ignore = true setting is suitable for a scenario where you don't know
80 ahead of time whether the pipe writer or the pipe reader will terminate
81 first. In this case, an EPIPE is an indication that the pipe writer can
82 stop doing useless write() calls; this is what close_stdout does anyway.
83 EPIPE is part of the normal pipe/socket shutdown protocol in this case,
84 and should not lead to a diagnostic message. */
85
86 void
87 close_stdout_set_ignore_EPIPE (bool ignore)
88 {
89 ignore_EPIPE = ignore;
90 }
91
92 /* Close standard output. On error, issue a diagnostic and _exit
93 with status 'exit_failure'.
94
95 Also close standard error. On error, _exit with status 'exit_failure'.
96
97 Since close_stdout is commonly registered via 'atexit', POSIX
98 and the C standard both say that it should not call 'exit',
99 because the behavior is undefined if 'exit' is called more than
100 once. So it calls '_exit' instead of 'exit'. If close_stdout
101 is registered via atexit before other functions are registered,
102 the other functions can act before this _exit is invoked.
103
104 Applications that use close_stdout should flush any streams
105 other than stdout and stderr before exiting, since the call to
106 _exit will bypass other buffer flushing. Applications should
107 be flushing and closing other streams anyway, to check for I/O
108 errors. Also, applications should not use tmpfile, since _exit
109 can bypass the removal of these files.
110
111 It's important to detect such failures and exit nonzero because many
112 tools (most notably 'make' and other build-management systems) depend
113 on being able to detect failure in other tools via their exit status. */
114
115 void
116 close_stdout (void)
117 {
118 if (close_stream (stdout) != 0
119 && !(ignore_EPIPE && errno == EPIPE))
120 {
121 char const *write_error = _("write error");
122 if (file_name)
123 error (0, errno, "%s: %s", quotearg_colon (file_name),
124 write_error);
125 else
126 error (0, errno, "%s", write_error);
127
128 _exit (exit_failure);
129 }
130
131 /* Close stderr only if not sanitizing, as sanitizers may report to
132 stderr after this function returns. */
133 if (!SANITIZE_ADDRESS && close_stream (stderr) != 0)
134 _exit (exit_failure);
135 }