tests/test-fflush2.c

   1 /* Test of POSIX compatible fflush() function.
   2    Copyright (C) 2008-2018 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 #include <stdio.h>
  20
  21 #include "binary-io.h"
  22 #include "macros.h"
  23
  24 int
  25 main (int argc, char **argv)
  26 {
  27   int c;
  28
  29   /* Avoid the well-known bugs of fflush() on streams in O_TEXT mode
  30      on native Windows platforms.  */
  31   set_binary_mode (0, O_BINARY);
  32
  33   if (argc > 1)
  34     switch (argv[1][0])
  35       {
  36       case '1':
  37         /* Check fflush after a backup ungetc() call.  This is case 1a in
  38            terms of
  39            <https://lists.gnu.org/r/bug-gnulib/2008-03/msg00131.html>,
  40            according to the Austin Group's resolution on 2009-01-08.  */
  41
  42         c = fgetc (stdin);
  43         ASSERT (c == '#');
  44
  45         c = fgetc (stdin);
  46         ASSERT (c == '!');
  47
  48         /* Here the file-position indicator must be 2.  */
  49
  50         c = ungetc ('!', stdin);
  51         ASSERT (c == '!');
  52
  53         fflush (stdin);
  54
  55         /* Here the file-position indicator must be 1.  */
  56
  57         c = fgetc (stdin);
  58         ASSERT (c == '!');
  59
  60         c = fgetc (stdin);
  61         ASSERT (c == '/');
  62
  63         return 0;
  64
  65       case '2':
  66         /* Check fflush after a non-backup ungetc() call.  This is case 2a in
  67            terms of
  68            <https://lists.gnu.org/r/bug-gnulib/2008-03/msg00131.html>,
  69            according to the Austin Group's resolution on 2009-01-08.  */
  70         /* Check that fflush after a non-backup ungetc() call discards the
  71            ungetc buffer.  This is mandated by POSIX
  72            <http://www.opengroup.org/susv3/functions/ungetc.html>:
  73              "The value of the file-position indicator for the stream after
  74               reading or discarding all pushed-back bytes shall be the same
  75               as it was before the bytes were pushed back."
  76            <http://www.opengroup.org/austin/aardvark/latest/xshbug3.txt>
  77              "[After fflush(),] the file offset of the underlying open file
  78               description shall be set to the file position of the stream, and
  79               any characters pushed back onto the stream by ungetc() or
  80               ungetwc() that have not subsequently been read from the stream
  81               shall be discarded."  */
  82
  83         c = fgetc (stdin);
  84         ASSERT (c == '#');
  85
  86         c = fgetc (stdin);
  87         ASSERT (c == '!');
  88
  89         /* Here the file-position indicator must be 2.  */
  90
  91         c = ungetc ('@', stdin);
  92         ASSERT (c == '@');
  93
  94         fflush (stdin);
  95
  96         /* Here the file-position indicator must be 1.  */
  97
  98         c = fgetc (stdin);
  99         ASSERT (c == '!');
 100
 101         c = fgetc (stdin);
 102         ASSERT (c == '/');
 103
 104         return 0;
 105       }
 106
 107   return 1;
 108 }