What is the canonical way to make autoconf link in Solaris network libraries?

Question

On Solaris, when you compile a program that uses sockets, you need to link it with -lnsl -lsocket. Many such programs were originally written for Linux (where no extra libraries are needed), and therefore do not check for these libraries in their configure scripts, even though that is a rather simple addition. Something like this (untested):

AC_SEARCH_LIBS(gethostbyname, nsl, , AC_MSG_ERROR([gethostbyname not found]))
AC_SEARCH_LIBS(connect, socket, , AC_MSG_ERROR([connect not found]))

Is there a canonical way to do this check? Maybe even included in the autoconf distribution? You would imagine that there is a rather widespread need for that, but Google wouldn't tell me.

Answer 1

I can't remember any finished code off the top of my head, but you usually want to check whether you can link a program calling the gethostbyname() function without any extra libs first. Only if that fails, you want to try the nsl library.

Similar things apply e.g. for the m library.

Answer 2

i think the closest to a canonical way to check this is the AX_LIB_SOCKET_NSL macro from the Autoconf Archive:

# ===========================================================================
#        http://www.nongnu.org/autoconf-archive/ax_lib_socket_nsl.html
# ===========================================================================
#
# SYNOPSIS
#
#   AX_LIB_SOCKET_NSL
#
# DESCRIPTION
#
#   This macro figures out what libraries are required on this platform to
#   link sockets programs.
#
#   The common cases are not to need any extra libraries, or to need
#   -lsocket and -lnsl. We need to avoid linking with libnsl unless we need
#   it, though, since on some OSes where it isn't necessary it will totally
#   break networking. Unisys also includes gethostbyname() in libsocket but
#   needs libnsl for socket().
#
# LICENSE
#
#   Copyright (c) 2008 Russ Allbery <[email protected]>
#   Copyright (c) 2008 Stepan Kasal <[email protected]>
#   Copyright (c) 2008 Warren Young <[email protected]>
#
#   Copying and distribution of this file, with or without modification, are
#   permitted in any medium without royalty provided the copyright notice
#   and this notice are preserved.

AU_ALIAS([LIB_SOCKET_NSL], [AX_LIB_SOCKET_NSL])
AC_DEFUN([AX_LIB_SOCKET_NSL],
[
        AC_SEARCH_LIBS([gethostbyname], [nsl])
        AC_SEARCH_LIBS([socket], [socket], [], [
                AC_CHECK_LIB([socket], [socket], [LIBS="-lsocket -lnsl $LIBS"],
                [], [-lnsl])])
])