Commit | Line | Data |
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7ccfb720 PE |
1 | /* Close a stream, with nicer error checking than fclose's. |
2 | ||
ba318903 | 3 | Copyright (C) 1998-2002, 2004, 2006-2014 Free Software Foundation, Inc. |
7ccfb720 PE |
4 | |
5 | This program is free software: you can redistribute it and/or modify | |
6 | it under the terms of the GNU General Public License as published by | |
7 | the Free Software Foundation; either version 3 of the License, or | |
8 | (at your option) any later version. | |
9 | ||
10 | This program is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | GNU General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU General Public License | |
16 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ | |
17 | ||
18 | #include <config.h> | |
19 | ||
20 | #include "close-stream.h" | |
21 | ||
22 | #include <errno.h> | |
23 | #include <stdbool.h> | |
24 | ||
25 | #include "fpending.h" | |
26 | ||
27 | #if USE_UNLOCKED_IO | |
28 | # include "unlocked-io.h" | |
29 | #endif | |
30 | ||
31 | /* Close STREAM. Return 0 if successful, EOF (setting errno) | |
32 | otherwise. A failure might set errno to 0 if the error number | |
33 | cannot be determined. | |
34 | ||
35 | A failure with errno set to EPIPE may or may not indicate an error | |
36 | situation worth signaling to the user. See the documentation of the | |
37 | close_stdout_set_ignore_EPIPE function for details. | |
38 | ||
39 | If a program writes *anything* to STREAM, that program should close | |
40 | STREAM and make sure that it succeeds before exiting. Otherwise, | |
41 | suppose that you go to the extreme of checking the return status | |
42 | of every function that does an explicit write to STREAM. The last | |
43 | printf can succeed in writing to the internal stream buffer, and yet | |
44 | the fclose(STREAM) could still fail (due e.g., to a disk full error) | |
45 | when it tries to write out that buffered data. Thus, you would be | |
46 | left with an incomplete output file and the offending program would | |
47 | exit successfully. Even calling fflush is not always sufficient, | |
48 | since some file systems (NFS and CODA) buffer written/flushed data | |
49 | until an actual close call. | |
50 | ||
51 | Besides, it's wasteful to check the return value from every call | |
52 | that writes to STREAM -- just let the internal stream state record | |
53 | the failure. That's what the ferror test is checking below. */ | |
54 | ||
55 | int | |
56 | close_stream (FILE *stream) | |
57 | { | |
58 | const bool some_pending = (__fpending (stream) != 0); | |
59 | const bool prev_fail = (ferror (stream) != 0); | |
60 | const bool fclose_fail = (fclose (stream) != 0); | |
61 | ||
62 | /* Return an error indication if there was a previous failure or if | |
63 | fclose failed, with one exception: ignore an fclose failure if | |
64 | there was no previous error, no data remains to be flushed, and | |
65 | fclose failed with EBADF. That can happen when a program like cp | |
66 | is invoked like this 'cp a b >&-' (i.e., with standard output | |
67 | closed) and doesn't generate any output (hence no previous error | |
68 | and nothing to be flushed). */ | |
69 | ||
70 | if (prev_fail || (fclose_fail && (some_pending || errno != EBADF))) | |
71 | { | |
72 | if (! fclose_fail) | |
73 | errno = 0; | |
74 | return EOF; | |
75 | } | |
76 | ||
77 | return 0; | |
78 | } |