1 /* Detect write error on a stream.
2 Copyright (C) 2003 Free Software Foundation, Inc.
3 Written by Bruno Haible <bruno@clisp.org>, 2003.
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 2, or (at your option)
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.
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, write to the Free Software Foundation,
17 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
24 #include "fwriteerror.h"
29 fwriteerror (FILE *fp)
32 1. test the error indicator of the stream,
33 2. flush the buffers (what fclose() would do), testing for error again.
34 We can equally well swap these steps; this leads to smaller code. */
36 /* Clear errno, so that on non-POSIX systems the caller doesn't see a
37 wrong value of errno when we return -1. */
41 return -1; /* errno is set here */
45 /* The stream had an error earlier, but its errno was lost. If the
46 error was not temporary, we can get the same errno by writing and
47 flushing one more byte. We can do so because at this point the
48 stream's contents is garbage anyway. */
49 if (fputc ('\0', fp) == EOF)
50 return -1; /* errno is set here */
52 return -1; /* errno is set here */
53 /* Give up on errno. */
64 /* Name of a file on which writing fails. On systems without /dev/full,
65 you can choose a filename on a full filesystem. */
66 #define UNWRITABLE_FILE "/dev/full"
79 static char dummy[8193];
82 for (i = 0; i < sizeof (sizes) / sizeof (sizes[0]); i++)
84 size_t size = sizes[i];
86 for (j = 0; j < 2; j++)
88 /* Run a test depending on i and j:
89 Write size bytes and then calls fflush if j==1. */
90 FILE *stream = fopen (UNWRITABLE_FILE, "w");
94 fprintf (stderr, "Test %u:%u: could not open file\n", i, j);
98 fwrite (dummy, 347, 1, stream);
99 fwrite (dummy, size - 347, 1, stream);
103 if (fwriteerror (stream) == -1)
106 fprintf (stderr, "Test %u:%u: fwriteerror ok, errno = %d\n",
110 fprintf (stderr, "Test %u:%u: fwriteerror found no error!\n",
114 fprintf (stderr, "Test %u:%u: fclose failed, errno = %d\n",