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