1# lseek.m4 serial 10
2dnl Copyright (C) 2007, 2009-2015 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7AC_DEFUN([gl_FUNC_LSEEK],
8[
9  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
10
11  AC_REQUIRE([AC_CANONICAL_HOST])
12  AC_REQUIRE([AC_PROG_CC])
13  AC_CHECK_HEADERS_ONCE([unistd.h])
14  AC_CACHE_CHECK([whether lseek detects pipes], [gl_cv_func_lseek_pipe],
15    [case "$host_os" in
16       mingw*)
17         dnl Native Windows.
18         dnl The result of lseek (fd, (off_t)0, SEEK_CUR) or
19         dnl SetFilePointer(handle, 0, NULL, FILE_CURRENT)
20         dnl for a pipe depends on the environment: In a Cygwin 1.5
21         dnl environment it succeeds (wrong); in a Cygwin 1.7 environment
22         dnl it fails with a wrong errno value.
23         gl_cv_func_lseek_pipe=no
24         ;;
25       *)
26         if test $cross_compiling = no; then
27           AC_LINK_IFELSE([AC_LANG_PROGRAM([[
28#include <sys/types.h> /* for off_t */
29#include <stdio.h> /* for SEEK_CUR */
30#if HAVE_UNISTD_H
31# include <unistd.h>
32#else /* on Windows with MSVC */
33# include <io.h>
34#endif
35]], [[
36  /* Exit with success only if stdin is seekable.  */
37  return lseek (0, (off_t)0, SEEK_CUR) < 0;
38]])],
39             [if test -s conftest$ac_exeext \
40                 && ./conftest$ac_exeext < conftest.$ac_ext \
41                 && test 1 = "`echo hi \
42                   | { ./conftest$ac_exeext; echo $?; cat >/dev/null; }`"; then
43                gl_cv_func_lseek_pipe=yes
44              else
45                gl_cv_func_lseek_pipe=no
46              fi
47             ],
48             [gl_cv_func_lseek_pipe=no])
49         else
50           AC_COMPILE_IFELSE(
51             [AC_LANG_SOURCE([[
52#if defined __BEOS__
53/* BeOS mistakenly return 0 when trying to seek on pipes.  */
54  Choke me.
55#endif]])],
56             [gl_cv_func_lseek_pipe=yes], [gl_cv_func_lseek_pipe=no])
57         fi
58         ;;
59     esac
60    ])
61  if test $gl_cv_func_lseek_pipe = no; then
62    REPLACE_LSEEK=1
63    AC_DEFINE([LSEEK_PIPE_BROKEN], [1],
64      [Define to 1 if lseek does not detect pipes.])
65  fi
66
67  AC_REQUIRE([gl_SYS_TYPES_H])
68  if test $WINDOWS_64_BIT_OFF_T = 1; then
69    REPLACE_LSEEK=1
70  fi
71])
72