autoconf: check for res_nquery explicitly

Creates a test that checks explicitly for res_nquery, which can be a
macro in resolv.h. Defines RESOLV_LIBS that contains any libraries that
need to be linked against.

Notes from later fix:

Based on the 2013-09-30 version of wip-port.  On FreeBSD, one must
include netinet/in.h to get the definitions for stuff in resolv.h.
Also, resolv.h's functions are part of libc instead of libresolv.

Signed-off-by: Alan Somers <[email protected]>
Signed-off-by: Noah Watkins <[email protected]>

configure.ac

@@ -118,8 +118,41 @@ AX_CXX_STATIC_CAST
 # Checks for libraries.
 ACX_PTHREAD
 AC_CHECK_LIB([uuid], [uuid_parse], [true], AC_MSG_FAILURE([libuuid not found]))
+
+#
+# Check for res_nquery in libresolv. There are several variations. On OSX
+# res_nquery is a macro defined in resolv.h, so the typical AC_CHECK_LIB
+# doesn't work. On FreeBSD res_nquery can be found in libc. The required
+# library for linking (if any) is defined RESOLV_LIBS.
+#
+AC_CHECK_HEADER([resolv.h], [], [], [#include <netinet/in.h>])
+
+AC_DEFUN([CHECK_RESOLV_LIBS], [{
+  AC_MSG_CHECKING([if res_nquery will link (LIBS=$1)])
+  saved_LIBS="${LIBS}"
+  LIBS="$1"
+  AC_LINK_IFELSE([AC_LANG_PROGRAM([[
+        #include <netinet/in.h>
+        #include <resolv.h>
+      ]], [[res_nquery(0, 0, 0, 0, 0, 0);]])],
+      [AC_MSG_RESULT([yes])
+      [$2]],
+      AC_MSG_RESULT([no]))
+  LIBS="${saved_LIBS}"
+}])
+
+RESOLV_LIBS=""
+CHECK_RESOLV_LIBS([$RESOLV_LIBS], [resolv_libs="ok"])
+if test x"$resolv_libs" != "xok"; then
+  RESOLV_LIBS="-lresolv"
+  CHECK_RESOLV_LIBS([$RESOLV_LIBS], [resolv_libs="ok"])
+  if test x"$resolv_libs" != "xok"; then
+    AC_MSG_FAILURE([no resolv library found])
+  fi
+fi
+AC_SUBST([RESOLV_LIBS])
+
 AC_CHECK_LIB([m], [pow], [true], AC_MSG_FAILURE([libm not found]))
-AC_CHECK_LIB([resolv], [__res_nquery], [true], AC_MSG_FAILURE([libresolv not found]))
 if test x"$linux" = x"yes"; then
 	AC_CHECK_LIB([keyutils], [add_key], [true], AC_MSG_FAILURE([libkeyutils not found]))
 fi

src/rgw/Makefile.am

@@ -68,7 +68,7 @@ radosgw_SOURCES = \
 	rgw/rgw_swift.cc \
 	rgw/rgw_swift_auth.cc \
 	rgw/rgw_main.cc
-radosgw_LDADD = $(LIBRGW) $(LIBRGW_DEPS) -lresolv $(CEPH_GLOBAL)
+radosgw_LDADD = $(LIBRGW) $(LIBRGW_DEPS) $(RESOLV_LIBS) $(CEPH_GLOBAL)
 bin_PROGRAMS += radosgw
 
 radosgw_admin_SOURCES = rgw/rgw_admin.cc