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annotate lib/closeout.c @ 6627:9e28dc7b0d44

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* closeout.c (close_stdout): Don't assume 'bool' converts nonzero ints to 0 or 1, as this isn't true for the stdbool.h substitute.
author Paul Eggert <eggert@cs.ucla.edu>
date Wed, 08 Feb 2006 00:04:23 +0000
parents 96c32553b4c6
children 3e074d71e4d1
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1 /* closeout.c - close standard output
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2
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3 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004, 2006 Free
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4 Software Foundation, Inc.
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5
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6 This program is free software; you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 2, or (at your option)
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9 any later version.
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10
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11 This program is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with this program; if not, write to the Free Software Foundation,
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18 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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19
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20 #ifdef HAVE_CONFIG_H
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21 # include <config.h>
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22 #endif
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23
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24 #include "closeout.h"
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25
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26 #include <stdio.h>
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27 #include <stdbool.h>
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28 #include <errno.h>
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29
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30 #include "gettext.h"
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31 #define _(msgid) gettext (msgid)
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32
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33 #include "error.h"
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34 #include "exitfail.h"
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35 #include "quotearg.h"
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36 #include "__fpending.h"
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37
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38 #if USE_UNLOCKED_IO
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39 # include "unlocked-io.h"
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40 #endif
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41
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42 static const char *file_name;
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43
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44 /* Set the file name to be reported in the event an error is detected
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45 by close_stdout. */
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46 void
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47 close_stdout_set_file_name (const char *file)
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48 {
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49 file_name = file;
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50 }
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51
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52 /* Close standard output, exiting with status 'exit_failure' on failure.
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53 If a program writes *anything* to stdout, that program should close
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54 stdout and make sure that it succeeds before exiting. Otherwise,
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55 suppose that you go to the extreme of checking the return status
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56 of every function that does an explicit write to stdout. The last
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57 printf can succeed in writing to the internal stream buffer, and yet
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58 the fclose(stdout) could still fail (due e.g., to a disk full error)
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59 when it tries to write out that buffered data. Thus, you would be
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60 left with an incomplete output file and the offending program would
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61 exit successfully. Even calling fflush is not always sufficient,
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62 since some file systems (NFS and CODA) buffer written/flushed data
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63 until an actual close call.
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64
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65 Besides, it's wasteful to check the return value from every call
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66 that writes to stdout -- just let the internal stream state record
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67 the failure. That's what the ferror test is checking below.
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68
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69 It's important to detect such failures and exit nonzero because many
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70 tools (most notably `make' and other build-management systems) depend
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71 on being able to detect failure in other tools via their exit status. */
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72
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73 void
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74 close_stdout (void)
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75 {
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76 bool none_pending = (__fpending (stdout) == 0);
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77 bool prev_fail = (ferror (stdout) != 0);
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78 bool fclose_fail = (fclose (stdout) != 0);
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79
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80 if (prev_fail || fclose_fail)
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81 {
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82 int e = fclose_fail ? errno : 0;
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83 char const *write_error;
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84
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85 /* If ferror returned zero, no data remains to be flushed, and we'd
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86 otherwise fail with EBADF due to a failed fclose, then assume that
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87 it's ok to ignore the fclose failure. That can happen when a
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88 program like cp is invoked like this `cp a b >&-' (i.e., with
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89 stdout closed) and doesn't generate any output (hence no previous
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90 error and nothing to be flushed). */
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91 if (e == EBADF && !prev_fail && none_pending)
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92 return;
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93
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94 write_error = _("write error");
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95 if (file_name)
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96 error (exit_failure, e, "%s: %s", quotearg_colon (file_name),
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97 write_error);
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98 else
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99 error (exit_failure, e, "%s", write_error);
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100 }
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101 }