wcsmbs/tst-fgetwc-after-eof.c

   1 /* Bug 1190: EOF conditions are supposed to be sticky.
   2    Copyright (C) 2018 Free Software Foundation.
   3    Copying and distribution of this file, with or without modification,
   4    are permitted in any medium without royalty provided the copyright
   5    notice and this notice are preserved. This file is offered as-is,
   6    without any warranty.  */
   7
   8 /* ISO C1999 specification of fgetwc:
   9
  10        #include <stdio.h>
  11        #include <wchar.h>
  12        wint_t fgetwc (FILE *stream);
  13
  14    Description
  15
  16      If the end-of-file indicator for the input stream pointed to by
  17      stream is not set and a next wide character is present, the
  18      fgetwc function obtains that wide character as a wchar_t
  19      converted to a wint_t and advances the associated file position
  20      indicator for the stream (if defined).
  21
  22   Returns
  23
  24      If the end-of-file indicator for the stream is set, or if the
  25      stream is at end-of-file, the end- of-file indicator for the
  26      stream is set and the fgetwc function returns WEOF. Otherwise,
  27      the fgetwc function returns the next wide character from the
  28      input stream pointed to by stream. If a read error occurs, the
  29      error indicator for the stream is set and the fgetwc function
  30      returns WEOF. If an encoding error occurs (including too few
  31      bytes), the value of the macro EILSEQ is stored in errno and the
  32      fgetwc function returns WEOF.
  33
  34    The requirement to return WEOF "if the end-of-file indicator for the
  35    stream is set" was new in C99; the language in the 1995 edition of
  36    the standard was ambiguous.  Historically, BSD-derived Unix always
  37    had the C99 behavior, whereas in System V fgetwc would attempt to
  38    call read() again before returning EOF again.  Prior to version 2.28,
  39    glibc followed the System V behavior even though this does not
  40    comply with C99.
  41
  42    See
  43    <https://sourceware.org/bugzilla/show_bug.cgi?id=1190>,
  44    <https://sourceware.org/bugzilla/show_bug.cgi?id=19476>,
  45    and the thread at
  46    <https://sourceware.org/ml/libc-alpha/2012-09/msg00343.html>
  47    for more detail.  */
  48
  49 #include <support/tty.h>
  50 #include <support/check.h>
  51
  52 #include <fcntl.h>
  53 #include <stdio.h>
  54 #include <stdlib.h>
  55 #include <string.h>
  56 #include <unistd.h>
  57 #include <wchar.h>
  58
  59 #define XWRITE(fd, s, msg) do {                         \
  60     if (write (fd, s, sizeof s - 1) != sizeof s - 1)    \
  61       {                                                 \
  62         perror ("write " msg);                          \
  63         return 1;                                       \
  64       }                                                 \
  65   } while (0)
  66
  67 int
  68 do_test (void)
  69 {
  70   /* The easiest way to set up the conditions under which you can
  71      notice whether the end-of-file indicator is sticky, is with a
  72      pseudo-tty.  This is also the case which applications are most
  73      likely to care about.  And it avoids any question of whether and
  74      how it is legitimate to access the same physical file with two
  75      independent FILE objects.  */
  76   int outer_fd, inner_fd;
  77   FILE *fp;
  78
  79   support_openpty (&outer_fd, &inner_fd, 0, 0, 0);
  80   fp = fdopen (inner_fd, "r+");
  81   if (!fp)
  82     {
  83       perror ("fdopen");
  84       return 1;
  85     }
  86
  87   XWRITE (outer_fd, "abc\n\004", "first line + EOF");
  88   TEST_COMPARE (fgetwc (fp), L'a');
  89   TEST_COMPARE (fgetwc (fp), L'b');
  90   TEST_COMPARE (fgetwc (fp), L'c');
  91   TEST_COMPARE (fgetwc (fp), L'\n');
  92   TEST_COMPARE (fgetwc (fp), WEOF);
  93
  94   TEST_VERIFY_EXIT (feof (fp));
  95   TEST_VERIFY_EXIT (!ferror (fp));
  96
  97   XWRITE (outer_fd, "d\n", "second line");
  98
  99   /* At this point, there is a new full line of input waiting in the
 100      kernelside input buffer, but we should still observe EOF from
 101      stdio, because the end-of-file indicator has not been cleared.  */
 102   TEST_COMPARE (fgetwc (fp), WEOF);
 103
 104   /* Clearing EOF should reveal the next line of input.  */
 105   clearerr (fp);
 106   TEST_COMPARE (fgetwc (fp), L'd');
 107   TEST_COMPARE (fgetwc (fp), L'\n');
 108
 109   fclose (fp);
 110   close (outer_fd);
 111   return 0;
 112 }
 113
 114 #include <support/test-driver.c>