1# select.m4 serial 7
2dnl Copyright (C) 2009-2014 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_SELECT],
8[
9  AC_REQUIRE([gl_HEADER_SYS_SELECT])
10  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
11  AC_REQUIRE([gl_SOCKETS])
12  if test "$ac_cv_header_winsock2_h" = yes; then
13    REPLACE_SELECT=1
14  else
15    dnl On Interix 3.5, select(0, NULL, NULL, NULL, timeout) fails with error
16    dnl EFAULT.
17    AC_CHECK_HEADERS_ONCE([sys/select.h])
18    AC_CACHE_CHECK([whether select supports a 0 argument],
19      [gl_cv_func_select_supports0],
20      [
21        AC_RUN_IFELSE([AC_LANG_SOURCE([[
22#include <sys/types.h>
23#include <sys/time.h>
24#if HAVE_SYS_SELECT_H
25#include <sys/select.h>
26#endif
27int main ()
28{
29  struct timeval timeout;
30  timeout.tv_sec = 0;
31  timeout.tv_usec = 5;
32  return select (0, (fd_set *)0, (fd_set *)0, (fd_set *)0, &timeout) < 0;
33}]])], [gl_cv_func_select_supports0=yes], [gl_cv_func_select_supports0=no],
34          [
35changequote(,)dnl
36           case "$host_os" in
37                       # Guess no on Interix.
38             interix*) gl_cv_func_select_supports0="guessing no";;
39                       # Guess yes otherwise.
40             *)        gl_cv_func_select_supports0="guessing yes";;
41           esac
42changequote([,])dnl
43          ])
44      ])
45    case "$gl_cv_func_select_supports0" in
46      *yes) ;;
47      *) REPLACE_SELECT=1 ;;
48    esac
49
50    dnl On FreeBSD 8.2, select() doesn't always reject bad fds.
51    AC_CACHE_CHECK([whether select detects invalid fds],
52      [gl_cv_func_select_detects_ebadf],
53      [
54        AC_RUN_IFELSE([AC_LANG_PROGRAM([[
55#include <sys/types.h>
56#include <sys/time.h>
57#if HAVE_SYS_SELECT_H
58# include <sys/select.h>
59#endif
60#include <unistd.h>
61#include <errno.h>
62]],[[
63  fd_set set;
64  dup2(0, 16);
65  FD_ZERO(&set);
66  FD_SET(16, &set);
67  close(16);
68  struct timeval timeout;
69  timeout.tv_sec = 0;
70  timeout.tv_usec = 5;
71  return select (17, &set, NULL, NULL, &timeout) != -1 || errno != EBADF;
72]])], [gl_cv_func_select_detects_ebadf=yes],
73      [gl_cv_func_select_detects_ebadf=no],
74          [
75           case "$host_os" in
76                    # Guess yes on glibc systems.
77            *-gnu*) gl_cv_func_select_detects_ebadf="guessing yes" ;;
78                    # If we don't know, assume the worst.
79            *)      gl_cv_func_select_detects_ebadf="guessing no" ;;
80           esac
81          ])
82      ])
83    case $gl_cv_func_select_detects_ebadf in
84      *yes) ;;
85      *) REPLACE_SELECT=1 ;;
86    esac
87  fi
88
89  dnl Determine the needed libraries.
90  LIB_SELECT="$LIBSOCKET"
91  if test $REPLACE_SELECT = 1; then
92    case "$host_os" in
93      mingw*)
94        dnl On the MSVC platform, the function MsgWaitForMultipleObjects
95        dnl (used in lib/select.c) requires linking with -luser32. On mingw,
96        dnl it is implicit.
97        AC_LINK_IFELSE(
98          [AC_LANG_SOURCE([[
99#define WIN32_LEAN_AND_MEAN
100#include <windows.h>
101int
102main ()
103{
104  MsgWaitForMultipleObjects (0, NULL, 0, 0, 0);
105  return 0;
106}]])],
107          [],
108          [LIB_SELECT="$LIB_SELECT -luser32"])
109        ;;
110    esac
111  fi
112  AC_SUBST([LIB_SELECT])
113])
114