1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
|
# fflush.m4
# serial 20
dnl Copyright (C) 2007-2025 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
dnl This file is offered as-is, without any warranty.
dnl From Eric Blake
dnl Find out how to obey POSIX semantics of fflush(stdin) discarding
dnl unread input on seekable streams, rather than C99 undefined semantics.
AC_DEFUN([gl_FUNC_FFLUSH],
[
AC_REQUIRE([gl_STDIO_H_DEFAULTS])
gl_FUNC_FFLUSH_STDIN
case "$gl_cv_func_fflush_stdin" in
*yes) ;;
*) REPLACE_FFLUSH=1 ;;
esac
])
dnl Determine whether fflush works on input streams.
dnl Sets gl_cv_func_fflush_stdin.
AC_DEFUN([gl_FUNC_FFLUSH_STDIN],
[
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_CHECK_HEADERS_ONCE([unistd.h])
AC_CACHE_CHECK([whether fflush works on input streams],
[gl_cv_func_fflush_stdin],
[echo hello world > conftest.txt
AC_RUN_IFELSE([AC_LANG_PROGRAM(
[[
#include <stdio.h>
#if HAVE_UNISTD_H
# include <unistd.h>
#else /* on Windows with MSVC */
# include <io.h>
#endif
]GL_MDA_DEFINES],
[[FILE *f = fopen ("conftest.txt", "r");
char buffer[10];
int fd;
int c;
if (f == NULL)
return 1;
fd = fileno (f);
if (fd < 0 || fread (buffer, 1, 5, f) != 5)
{ fclose (f); return 2; }
/* For deterministic results, ensure f read a bigger buffer. */
if (lseek (fd, 0, SEEK_CUR) == 5)
{ fclose (f); return 3; }
/* POSIX requires fflush-fseek to set file offset of fd. This fails
on BSD systems and on mingw. */
if (fflush (f) != 0 || fseek (f, 0, SEEK_CUR) != 0)
{ fclose (f); return 4; }
if (lseek (fd, 0, SEEK_CUR) != 5)
{ fclose (f); return 5; }
/* Verify behaviour of fflush after ungetc. See
<https://www.opengroup.org/austin/aardvark/latest/xshbug3.txt> */
/* Verify behaviour of fflush after a backup ungetc. This fails on
mingw. */
c = fgetc (f);
ungetc (c, f);
fflush (f);
if (fgetc (f) != c)
{ fclose (f); return 6; }
/* Verify behaviour of fflush after a non-backup ungetc. This fails
on glibc 2.8 and on BSD systems. */
c = fgetc (f);
ungetc ('@', f);
fflush (f);
if (fgetc (f) != c)
{ fclose (f); return 7; }
fclose (f);
return 0;
]])],
[gl_cv_func_fflush_stdin=yes],
[gl_cv_func_fflush_stdin=no],
[case "$host_os" in
# Guess no on NetBSD, OpenBSD, native Windows.
netbsd* | openbsd* | mingw* | windows*)
gl_cv_func_fflush_stdin="guessing no" ;;
*) gl_cv_func_fflush_stdin=cross ;;
esac
])
rm conftest.txt
])
case "$gl_cv_func_fflush_stdin" in
*yes) gl_func_fflush_stdin=1 ;;
*no) gl_func_fflush_stdin=0 ;;
*) gl_func_fflush_stdin='(-1)' ;;
esac
AC_DEFINE_UNQUOTED([FUNC_FFLUSH_STDIN], [$gl_func_fflush_stdin],
[Define to 1 if fflush is known to work on stdin as per POSIX.1-2008
or later, 0 if fflush is known to not work, -1 if unknown.])
])
# Prerequisites of lib/fflush.c.
AC_DEFUN([gl_PREREQ_FFLUSH], [:])
|
