1*63eb84d1Schristos /* Detect write error on a stream.
2*63eb84d1Schristos Copyright (C) 2003-2006 Free Software Foundation, Inc.
3*63eb84d1Schristos Written by Bruno Haible <bruno@clisp.org>, 2003.
4*63eb84d1Schristos
5*63eb84d1Schristos This program is free software; you can redistribute it and/or modify
6*63eb84d1Schristos it under the terms of the GNU General Public License as published by
7*63eb84d1Schristos the Free Software Foundation; either version 2, or (at your option)
8*63eb84d1Schristos any later version.
9*63eb84d1Schristos
10*63eb84d1Schristos This program is distributed in the hope that it will be useful,
11*63eb84d1Schristos but WITHOUT ANY WARRANTY; without even the implied warranty of
12*63eb84d1Schristos MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13*63eb84d1Schristos GNU General Public License for more details.
14*63eb84d1Schristos
15*63eb84d1Schristos You should have received a copy of the GNU General Public License
16*63eb84d1Schristos along with this program; if not, write to the Free Software Foundation,
17*63eb84d1Schristos Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
18*63eb84d1Schristos
19*63eb84d1Schristos #include <config.h>
20*63eb84d1Schristos
21*63eb84d1Schristos /* Specification. */
22*63eb84d1Schristos #include "fwriteerror.h"
23*63eb84d1Schristos
24*63eb84d1Schristos #include <errno.h>
25*63eb84d1Schristos #include <stdbool.h>
26*63eb84d1Schristos
27*63eb84d1Schristos static int
do_fwriteerror(FILE * fp,bool ignore_ebadf)28*63eb84d1Schristos do_fwriteerror (FILE *fp, bool ignore_ebadf)
29*63eb84d1Schristos {
30*63eb84d1Schristos /* State to allow multiple calls to fwriteerror (stdout). */
31*63eb84d1Schristos static bool stdout_closed = false;
32*63eb84d1Schristos
33*63eb84d1Schristos if (fp == stdout)
34*63eb84d1Schristos {
35*63eb84d1Schristos if (stdout_closed)
36*63eb84d1Schristos return 0;
37*63eb84d1Schristos
38*63eb84d1Schristos /* If we are closing stdout, don't attempt to do it later again. */
39*63eb84d1Schristos stdout_closed = true;
40*63eb84d1Schristos }
41*63eb84d1Schristos
42*63eb84d1Schristos /* Need to
43*63eb84d1Schristos 1. test the error indicator of the stream,
44*63eb84d1Schristos 2. flush the buffers both in userland and in the kernel, through fclose,
45*63eb84d1Schristos testing for error again. */
46*63eb84d1Schristos
47*63eb84d1Schristos /* Clear errno, so that on non-POSIX systems the caller doesn't see a
48*63eb84d1Schristos wrong value of errno when we return -1. */
49*63eb84d1Schristos errno = 0;
50*63eb84d1Schristos
51*63eb84d1Schristos if (ferror (fp))
52*63eb84d1Schristos {
53*63eb84d1Schristos if (fflush (fp))
54*63eb84d1Schristos goto close_preserving_errno; /* errno is set here */
55*63eb84d1Schristos /* The stream had an error earlier, but its errno was lost. If the
56*63eb84d1Schristos error was not temporary, we can get the same errno by writing and
57*63eb84d1Schristos flushing one more byte. We can do so because at this point the
58*63eb84d1Schristos stream's contents is garbage anyway. */
59*63eb84d1Schristos if (fputc ('\0', fp) == EOF)
60*63eb84d1Schristos goto close_preserving_errno; /* errno is set here */
61*63eb84d1Schristos if (fflush (fp))
62*63eb84d1Schristos goto close_preserving_errno; /* errno is set here */
63*63eb84d1Schristos /* Give up on errno. */
64*63eb84d1Schristos errno = 0;
65*63eb84d1Schristos goto close_preserving_errno;
66*63eb84d1Schristos }
67*63eb84d1Schristos
68*63eb84d1Schristos if (ignore_ebadf)
69*63eb84d1Schristos {
70*63eb84d1Schristos /* We need an explicit fflush to tell whether some output was already
71*63eb84d1Schristos done on FP. */
72*63eb84d1Schristos if (fflush (fp))
73*63eb84d1Schristos goto close_preserving_errno; /* errno is set here */
74*63eb84d1Schristos if (fclose (fp) && errno != EBADF)
75*63eb84d1Schristos return -1; /* errno is set here */
76*63eb84d1Schristos }
77*63eb84d1Schristos else
78*63eb84d1Schristos {
79*63eb84d1Schristos if (fclose (fp))
80*63eb84d1Schristos return -1; /* errno is set here */
81*63eb84d1Schristos }
82*63eb84d1Schristos
83*63eb84d1Schristos return 0;
84*63eb84d1Schristos
85*63eb84d1Schristos close_preserving_errno:
86*63eb84d1Schristos /* There's an error. Nevertheless call fclose(fp), for consistency
87*63eb84d1Schristos with the other cases. */
88*63eb84d1Schristos {
89*63eb84d1Schristos int saved_errno = errno;
90*63eb84d1Schristos fclose (fp);
91*63eb84d1Schristos errno = saved_errno;
92*63eb84d1Schristos return -1;
93*63eb84d1Schristos }
94*63eb84d1Schristos }
95*63eb84d1Schristos
96*63eb84d1Schristos int
fwriteerror(FILE * fp)97*63eb84d1Schristos fwriteerror (FILE *fp)
98*63eb84d1Schristos {
99*63eb84d1Schristos return do_fwriteerror (fp, false);
100*63eb84d1Schristos }
101*63eb84d1Schristos
102*63eb84d1Schristos int
fwriteerror_no_ebadf(FILE * fp)103*63eb84d1Schristos fwriteerror_no_ebadf (FILE *fp)
104*63eb84d1Schristos {
105*63eb84d1Schristos return do_fwriteerror (fp, true);
106*63eb84d1Schristos }
107*63eb84d1Schristos
108*63eb84d1Schristos
109*63eb84d1Schristos #if TEST
110*63eb84d1Schristos
111*63eb84d1Schristos /* Name of a file on which writing fails. On systems without /dev/full,
112*63eb84d1Schristos you can choose a filename on a full filesystem. */
113*63eb84d1Schristos #define UNWRITABLE_FILE "/dev/full"
114*63eb84d1Schristos
115*63eb84d1Schristos int
main()116*63eb84d1Schristos main ()
117*63eb84d1Schristos {
118*63eb84d1Schristos static int sizes[] =
119*63eb84d1Schristos {
120*63eb84d1Schristos 511, 512, 513,
121*63eb84d1Schristos 1023, 1024, 1025,
122*63eb84d1Schristos 2047, 2048, 2049,
123*63eb84d1Schristos 4095, 4096, 4097,
124*63eb84d1Schristos 8191, 8192, 8193
125*63eb84d1Schristos };
126*63eb84d1Schristos static char dummy[8193];
127*63eb84d1Schristos unsigned int i, j;
128*63eb84d1Schristos
129*63eb84d1Schristos for (i = 0; i < sizeof (sizes) / sizeof (sizes[0]); i++)
130*63eb84d1Schristos {
131*63eb84d1Schristos size_t size = sizes[i];
132*63eb84d1Schristos
133*63eb84d1Schristos for (j = 0; j < 2; j++)
134*63eb84d1Schristos {
135*63eb84d1Schristos /* Run a test depending on i and j:
136*63eb84d1Schristos Write size bytes and then calls fflush if j==1. */
137*63eb84d1Schristos FILE *stream = fopen (UNWRITABLE_FILE, "w");
138*63eb84d1Schristos
139*63eb84d1Schristos if (stream == NULL)
140*63eb84d1Schristos {
141*63eb84d1Schristos fprintf (stderr, "Test %u:%u: could not open file\n", i, j);
142*63eb84d1Schristos continue;
143*63eb84d1Schristos }
144*63eb84d1Schristos
145*63eb84d1Schristos fwrite (dummy, 347, 1, stream);
146*63eb84d1Schristos fwrite (dummy, size - 347, 1, stream);
147*63eb84d1Schristos if (j)
148*63eb84d1Schristos fflush (stream);
149*63eb84d1Schristos
150*63eb84d1Schristos if (fwriteerror (stream) == -1)
151*63eb84d1Schristos {
152*63eb84d1Schristos if (errno != ENOSPC)
153*63eb84d1Schristos fprintf (stderr, "Test %u:%u: fwriteerror ok, errno = %d\n",
154*63eb84d1Schristos i, j, errno);
155*63eb84d1Schristos }
156*63eb84d1Schristos else
157*63eb84d1Schristos fprintf (stderr, "Test %u:%u: fwriteerror found no error!\n",
158*63eb84d1Schristos i, j);
159*63eb84d1Schristos }
160*63eb84d1Schristos }
161*63eb84d1Schristos
162*63eb84d1Schristos return 0;
163*63eb84d1Schristos }
164*63eb84d1Schristos
165*63eb84d1Schristos #endif
166