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# select.m4 serial 12
dnl Copyright (C) 2009-2021 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_SELECT],
[
AC_REQUIRE([gl_HEADER_SYS_SELECT])
AC_REQUIRE([AC_C_RESTRICT])
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_REQUIRE([gl_SOCKETS])
if test "$ac_cv_header_winsock2_h" = yes; then
REPLACE_SELECT=1
else
dnl On Interix 3.5, select(0, NULL, NULL, NULL, timeout) fails with error
dnl EFAULT.
AC_CHECK_HEADERS_ONCE([sys/select.h])
AC_CACHE_CHECK([whether select supports a 0 argument],
[gl_cv_func_select_supports0],
[
AC_RUN_IFELSE([AC_LANG_SOURCE([[
#include <sys/types.h>
#include <sys/time.h>
#if HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
int main ()
{
struct timeval timeout;
timeout.tv_sec = 0;
timeout.tv_usec = 5;
return select (0, (fd_set *)0, (fd_set *)0, (fd_set *)0, &timeout) < 0;
}]])], [gl_cv_func_select_supports0=yes], [gl_cv_func_select_supports0=no],
[
changequote(,)dnl
case "$host_os" in
# Guess no on Interix.
interix*) gl_cv_func_select_supports0="guessing no";;
# Guess yes otherwise.
*) gl_cv_func_select_supports0="guessing yes";;
esac
changequote([,])dnl
])
])
case "$gl_cv_func_select_supports0" in
*yes) ;;
*) REPLACE_SELECT=1 ;;
esac
dnl On FreeBSD 8.2, select() doesn't always reject bad fds.
AC_CACHE_CHECK([whether select detects invalid fds],
[gl_cv_func_select_detects_ebadf],
[
AC_RUN_IFELSE([AC_LANG_PROGRAM([[
#include <sys/types.h>
#include <sys/time.h>
#if HAVE_SYS_SELECT_H
# include <sys/select.h>
#endif
#include <unistd.h>
#include <errno.h>
]GL_MDA_DEFINES],
[[
fd_set set;
dup2(0, 16);
FD_ZERO(&set);
FD_SET(16, &set);
close(16);
struct timeval timeout;
timeout.tv_sec = 0;
timeout.tv_usec = 5;
return select (17, &set, NULL, NULL, &timeout) != -1 || errno != EBADF;
]])], [gl_cv_func_select_detects_ebadf=yes],
[gl_cv_func_select_detects_ebadf=no],
[
case "$host_os" in
# Guess yes on Linux systems.
linux-* | linux) gl_cv_func_select_detects_ebadf="guessing yes" ;;
# Guess yes on glibc systems.
*-gnu* | gnu*) gl_cv_func_select_detects_ebadf="guessing yes" ;;
# If we don't know, obey --enable-cross-guesses.
*) gl_cv_func_select_detects_ebadf="$gl_cross_guess_normal" ;;
esac
])
])
case $gl_cv_func_select_detects_ebadf in
*yes) ;;
*) REPLACE_SELECT=1 ;;
esac
fi
dnl Determine the needed libraries.
LIB_SELECT="$LIBSOCKET"
if test $REPLACE_SELECT = 1; then
case "$host_os" in
mingw*)
dnl On the MSVC platform, the function MsgWaitForMultipleObjects
dnl (used in lib/select.c) requires linking with -luser32. On mingw,
dnl it is implicit.
AC_LINK_IFELSE(
[AC_LANG_SOURCE([[
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
int
main ()
{
MsgWaitForMultipleObjects (0, NULL, 0, 0, 0);
return 0;
}]])],
[],
[LIB_SELECT="$LIB_SELECT -luser32"])
;;
esac
fi
AC_SUBST([LIB_SELECT])
])
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