fixed build configuration test in session.cpp

include/libtorrent/config.hpp

@@ -39,7 +39,14 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <limits.h> // for IOV_MAX
 
 #if defined TORRENT_DEBUG_BUFFERS && !defined TORRENT_DISABLE_POOL_ALLOCATOR
-#error TORRENT_DEBUG_BUFFERS only works if you also disable pool allocators
+#error TORRENT_DEBUG_BUFFERS only works if you also disable pool allocators with TORRENT_DISABLE_POOL_ALLOCATOR
+#endif
+
+#if !defined BOOST_ASIO_SEPARATE_COMPILATION && !defined BOOST_ASIO_DYN_LINK
+#error you must define either BOOST_ASIO_SEPARATE_COMPILATION or BOOST_ASIO_DYN_LINK in your project in \
+	order for asio's declarations to be correct. If you're linking dynamically against libtorrent, define \
+	BOOST_ASIO_DYN_LINK otherwise BOOST_ASIO_SEPARATE_COMPILATION. You can also use pkg-config or boost \
+	build, to automatically apply these defines
 #endif
 
 #ifndef _MSC_VER

include/libtorrent/session.hpp

@@ -57,6 +57,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/alert.hpp" // alert::error_notification
 #include "libtorrent/add_torrent_params.hpp"
 #include "libtorrent/rss.hpp"
+#include "libtorrent/build_config.hpp"
 
 #include "libtorrent/storage.hpp"
 
@@ -86,6 +87,10 @@ namespace libtorrent
 	TORRENT_EXPORT session_settings min_memory_usage();
 	TORRENT_EXPORT session_settings high_performance_seed();
 
+#ifndef TORRENT_CFG
+#error TORRENT_CFG is not defined!
+#endif
+
 	void TORRENT_EXPORT TORRENT_CFG();
 
 	namespace aux

src/session.cpp

@@ -376,6 +376,10 @@ namespace libtorrent
 	m_impl->m_io_service.post(boost::bind(&fun_ret<type>, &r, &done, &m_impl->cond, &m_impl->mut, boost::function<type(void)>(boost::bind(&session_impl:: x, m_impl.get(), a1, a2, a3)))); \
 	TORRENT_WAIT
 
+#ifndef TORRENT_CFG
+#error TORRENT_CFG is not defined!
+#endif
+
 	// this is a dummy function that's exported and named based
 	// on the configuration. The session.hpp file will reference
 	// it and if the library and the client are built with different