tests/test-fflush2.c

   1 /* Test of POSIX compatible fflush() function.
   2    Copyright (C) 2008-2024 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 test_exit_status;
  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            <https://pubs.opengroup.org/onlinepubs/9699919799/functions/fflush.html>:
  73              "...any characters pushed back onto the stream by ungetc()
  74               or ungetwc() that have not subsequently been read from the
  75               stream shall be discarded..."  */
  76
  77         c = fgetc (stdin);
  78         ASSERT (c == '#');
  79
  80         c = fgetc (stdin);
  81         ASSERT (c == '!');
  82
  83         /* Here the file-position indicator must be 2.  */
  84
  85         c = ungetc ('@', stdin);
  86         ASSERT (c == '@');
  87
  88         fflush (stdin);
  89
  90         /* Here the file-position indicator must be 1.  */
  91
  92         c = fgetc (stdin);
  93         ASSERT (c == '!');
  94
  95         c = fgetc (stdin);
  96         ASSERT (c == '/');
  97
  98         return test_exit_status;
  99       }
 100
 101   return 1;
 102 }