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# lseek.m4 serial 14
dnl Copyright (C) 2007, 2009-2023 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.
AC_DEFUN([gl_FUNC_LSEEK],
[
AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
AC_REQUIRE([AC_CANONICAL_HOST])
AC_REQUIRE([AC_PROG_CC])
AC_CHECK_HEADERS_ONCE([unistd.h])
AC_CACHE_CHECK([whether lseek detects pipes], [gl_cv_func_lseek_pipe],
[case "$host_os" in
mingw*)
dnl Native Windows.
dnl The result of lseek (fd, (off_t)0, SEEK_CUR) or
dnl SetFilePointer(handle, 0, NULL, FILE_CURRENT)
dnl for a pipe depends on the environment:
dnl In a Cygwin 1.5 environment it succeeds (wrong);
dnl in a Cygwin 1.7 environment it fails with a wrong errno value;
dnl in a Cygwin 2.9.0 environment it fails correctly;
dnl in a Cygwin 3.4.6 environment it succeeds again (wrong).
gl_cv_func_lseek_pipe=no
;;
*)
if test $cross_compiling = no; then
AC_LINK_IFELSE([AC_LANG_PROGRAM([[
#include <sys/types.h> /* for off_t */
#include <stdio.h> /* for SEEK_CUR */
#if HAVE_UNISTD_H
# include <unistd.h>
#else /* on Windows with MSVC */
# include <io.h>
#endif
]GL_MDA_DEFINES],
[[
/* Exit with success only if stdin is seekable. */
return lseek (0, (off_t)0, SEEK_CUR) < 0;
]])],
[if test -s conftest$ac_exeext \
&& ./conftest$ac_exeext < conftest.$ac_ext \
&& test 1 = "`echo hi \
| { ./conftest$ac_exeext; echo $?; cat >/dev/null; }`"; then
gl_cv_func_lseek_pipe=yes
else
gl_cv_func_lseek_pipe=no
fi
],
[gl_cv_func_lseek_pipe=no])
else
AC_COMPILE_IFELSE(
[AC_LANG_SOURCE([[
#if defined __BEOS__
/* BeOS mistakenly return 0 when trying to seek on pipes. */
Choke me.
#endif]])],
[gl_cv_func_lseek_pipe=yes], [gl_cv_func_lseek_pipe=no])
fi
;;
esac
])
if test "$gl_cv_func_lseek_pipe" = no; then
REPLACE_LSEEK=1
AC_DEFINE([LSEEK_PIPE_BROKEN], [1],
[Define to 1 if lseek does not detect pipes.])
fi
AC_REQUIRE([gl_SYS_TYPES_H])
if test $WINDOWS_64_BIT_OFF_T = 1; then
REPLACE_LSEEK=1
fi
AS_IF([test $REPLACE_LSEEK = 0],
[AC_CACHE_CHECK([whether SEEK_DATA works but is incompatible with GNU],
[gl_cv_func_lseek_works_but_incompatible],
[AC_PREPROC_IFELSE(
[AC_LANG_SOURCE(
dnl Use macOS "9999" to stand for a future fixed macOS version.
dnl See ../lib/unistd.in.h and <https://bugs.gnu.org/61386>.
[[#include <unistd.h>
#if defined __APPLE__ && defined __MACH__ && defined SEEK_DATA
# ifdef __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__
# include <AvailabilityMacros.h>
# endif
# if 99990000 <= MAC_OS_X_VERSION_MIN_REQUIRED
# define LSEEK_WORKS_BUT_IS_INCOMPATIBLE_WITH_GNU
# endif
#endif
#ifndef LSEEK_WORKS_BUT_IS_INCOMPATIBLE_WITH_GNU
#error "No need to work around the bug"
#endif
]])],
[gl_cv_func_lseek_works_but_incompatible=yes],
[gl_cv_func_lseek_works_but_incompatible=no])])
if test "$gl_cv_func_lseek_works_but_incompatible" = yes; then
REPLACE_LSEEK=1
fi])
])
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