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
do_test(void)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>
115