Failure to use -lnsl on Solaris with AC_CHECK_LIB

[Warren Young]

I have an AC_CHECK_LIB test that checks for the MySQL C API client 
library.  It's working fine on most systems, but it's failing for one 
user on a Solaris 8 box with GNU tools added from sunfreeware.com.

On examining config.log, we find that the test fails because autoconf 
isn't also adding -lnsl to the link line when building the test program. 
 Since the MySQL library depends on network access, the test program 
can't be linked, which is the same symptom as "no MySQL library".  The 
test is therefore useless on this platform.

We'd rather not explicitly add -lnsl to our autoconf test, because we're 
under the impression that this is one of those things that autoconf is 
supposed to handle automatically.  Are we wrong?  Is there something 
besides explicitly adding that library to the LDFLAGS variable that we 
should be doing instead?

I've attached our autoconf test, in case it helps.

dnl @synopsis MYSQL_API_LOCATION
dnl 
dnl This macro tries to find MySQL C API header and library locations.
dnl
dnl We define the following configure script flags:
dnl
dnl             --with-mysql: Give prefix for both library and headers, and try
dnl                     to guess subdirectory names for each.  (e.g. Tack /lib 
and
dnl                     /include onto given dir name, and other common schemes.)
dnl             --with-mysql-lib: Similar to --with-mysql, but for library only.
dnl             --with-mysql-include: Similar to --with-mysql, but for headers
dnl                     only.
dnl
dnl @version 1.1, 2005/02/28
dnl @author Warren Young <address@hidden>
AC_DEFUN([MYSQL_API_LOCATION],
[
        #
        # Set up configure script macros
        #
        AC_ARG_WITH(mysql,
                [  --with-mysql=<path>     root directory path of MySQL 
installation],
                [MYSQL_lib_check="$with_mysql/lib/mysql $with_mysql/lib"
                MYSQL_inc_check="$with_mysql/include 
$with_mysql/include/mysql"],
                [MYSQL_lib_check="/usr/local/mysql/lib/mysql 
/usr/local/lib/mysql /opt/mysql/lib/mysql /usr/lib/mysql /usr/local/mysql/lib 
/usr/local/lib /opt/mysql/lib /usr/lib"
                MYSQL_inc_check="/usr/local/mysql/include/mysql 
/usr/local/include/mysql /opt/mysql/include/mysql /usr/include/mysql"])
        AC_ARG_WITH(mysql-lib,
                [  --with-mysql-lib=<path> directory path of MySQL library 
installation],
                [MYSQL_lib_check="$with_mysql_lib $with_mysql_lib/lib 
$with_mysql_lib/lib/mysql"])
        AC_ARG_WITH(mysql-include,
                [  --with-mysql-include=<path> directory path of MySQL header 
installation],
                [MYSQL_inc_check="$with_mysql_include 
$with_mysql_include/include $with_mysql_include/include/mysql"])

        #
        # Decide which C API library to use, based on thread support
        #
        if test "x$acx_pthread_ok" = xyes
        then
                MYSQL_C_LIB=mysqlclient_r
        else
                MYSQL_C_LIB=mysqlclient
        fi

        #
        # Look for MySQL C API library
        #
        AC_MSG_CHECKING([for MySQL library directory])
        MYSQL_libdir=
        for m in $MYSQL_lib_check
        do
                if test -d "$m" && \
                        (test -f "$m/lib$MYSQL_C_LIB.so" || test -f 
"$m/lib$MYSQL_C_LIB.a")
                then
                        MYSQL_libdir=$m
                        break
                fi
        done

        if test -z "$MYSQL_libdir"
        then
                AC_MSG_ERROR([Didn't find $MYSQL_C_LIB library in 
'$MYSQL_lib_check'])
        fi

        case "$MYSQL_libdir" in
                /* ) ;;
                * )  AC_MSG_ERROR([The MySQL library directory ($MYSQL_libdir) 
must be an absolute path.]) ;;
        esac

        AC_MSG_RESULT([$MYSQL_libdir])

        case "$MYSQL_libdir" in
          /usr/lib) ;;
          *) LDFLAGS="$LDFLAGS -L${MYSQL_libdir}" ;;
        esac


        #
        # Look for MySQL C API headers
        #
        AC_MSG_CHECKING([for MySQL include directory])
        MYSQL_incdir=
        for m in $MYSQL_inc_check
        do
                if test -d "$m" && test -f "$m/mysql.h"
                then
                        MYSQL_incdir=$m
                        break
                fi
        done

        if test -z "$MYSQL_incdir"
        then
                AC_MSG_ERROR([Didn't find the MySQL include dir in 
'$MYSQL_inc_check'])
        fi

        case "$MYSQL_incdir" in
                /* ) ;;
                * )  AC_MSG_ERROR([The MySQL include directory ($MYSQL_incdir) 
must be an absolute path.]) ;;
        esac

        AC_MSG_RESULT([$MYSQL_incdir])

        CPPFLAGS="$CPPFLAGS -I${MYSQL_incdir}"

        AC_CHECK_LIB($MYSQL_C_LIB, mysql_store_result, [], [
                        AC_MSG_ERROR([Could not find working MySQL client 
library!]) ])
        AC_SUBST(MYSQL_C_LIB)
]) dnl MYSQL_API_LOCATION