gnu/dist/gettext/gettext-tools/lib/fwriteerror.c

   1 /* Detect write error on a stream.
   2    Copyright (C) 2003-2005 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2003.
   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 2, or (at your option)
   8    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, write to the Free Software Foundation,
  17    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  18
  19 #if HAVE_CONFIG_H
  20 # include <config.h>
  21 #endif
  22
  23 /* Specification.  */
  24 #include "fwriteerror.h"
  25
  26 #include <errno.h>
  27 #include <stdbool.h>
  28
  29 int
  30 fwriteerror (FILE *fp)
  31 {
  32   /* State to allow multiple calls to fwriteerror (stdout).  */
  33   static bool stdout_closed = false;
  34
  35   if (fp == stdout && stdout_closed)
  36     return 0;
  37
  38   /* Need to
  39      1. test the error indicator of the stream,
  40      2. flush the buffers both in userland and in the kernel, through fclose,
  41         testing for error again.  */
  42
  43   /* Clear errno, so that on non-POSIX systems the caller doesn't see a
  44      wrong value of errno when we return -1.  */
  45   errno = 0;
  46
  47   if (ferror (fp))
  48     {
  49       if (fflush (fp))
  50         return -1; /* errno is set here */
  51       /* The stream had an error earlier, but its errno was lost.  If the
  52          error was not temporary, we can get the same errno by writing and
  53          flushing one more byte.  We can do so because at this point the
  54          stream's contents is garbage anyway.  */
  55       if (fputc ('\0', fp) == EOF)
  56         return -1; /* errno is set here */
  57       if (fflush (fp))
  58         return -1; /* errno is set here */
  59       /* Give up on errno.  */
  60       errno = 0;
  61       return -1;
  62     }
  63
  64   /* If we are closing stdout, don't attempt to do it later again.  */
  65   if (fp == stdout)
  66     stdout_closed = true;
  67
  68   if (fclose (fp))
  69     return -1; /* errno is set here */
  70
  71   return 0;
  72 }
  73
  74
  75 #if TEST
  76
  77 /* Name of a file on which writing fails.  On systems without /dev/full,
  78    you can choose a filename on a full filesystem.  */
  79 #define UNWRITABLE_FILE "/dev/full"
  80
  81 int
  82 main ()
  83 {
  84   static int sizes[] =
  85     {
  86        511,  512,  513,
  87       1023, 1024, 1025,
  88       2047, 2048, 2049,
  89       4095, 4096, 4097,
  90       8191, 8192, 8193
  91     };
  92   static char dummy[8193];
  93   unsigned int i, j;
  94
  95   for (i = 0; i < sizeof (sizes) / sizeof (sizes[0]); i++)
  96     {
  97       size_t size = sizes[i];
  98
  99       for (j = 0; j < 2; j++)
 100         {
 101           /* Run a test depending on i and j:
 102              Write size bytes and then calls fflush if j==1.  */
 103           FILE *stream = fopen (UNWRITABLE_FILE, "w");
 104
 105           if (stream == NULL)
 106             {
 107               fprintf (stderr, "Test %u:%u: could not open file\n", i, j);
 108               continue;
 109             }
 110
 111           fwrite (dummy, 347, 1, stream);
 112           fwrite (dummy, size - 347, 1, stream);
 113           if (j)
 114             fflush (stream);
 115
 116           if (fwriteerror (stream) == -1)
 117             {
 118               if (errno != ENOSPC)
 119                 fprintf (stderr, "Test %u:%u: fwriteerror ok, errno = %d\n",
 120                          i, j, errno);
 121             }
 122           else
 123             fprintf (stderr, "Test %u:%u: fwriteerror found no error!\n",
 124                      i, j);
 125         }
 126     }
 127
 128   return 0;
 129 }
 130
 131 #endif