On -current from two days ago, with up-to-date pkgsrc (HEAD), I get:

c++ -O2 -I/usr/pkgsrc/devel/glibmm/work/.buildlink/include -Wall -Wno-long-long 
-Wl,-R/usr/pkg/lib -o .libs/parser parser.o -Wl,--export-dynamic  -L/usr/pkgsrc/
devel/glibmm/work/.buildlink/lib ../../glib/glibmm/.libs/libglibmm-2.4.so /usr/p
kgsrc/devel/glibmm/work/.buildlink/lib/libsigc-2.0.so /usr/pkgsrc/devel/glibmm/w
ork/.buildlink/lib/libgobject-2.0.so /usr/pkgsrc/devel/glibmm/work/.buildlink/li
b/libgmodule-2.0.so /usr/pkgsrc/devel/glibmm/work/.buildlink/lib/libglib-2.0.so 
-lintl -Wl,--rpath -Wl,/usr/pkg/lib -Wl,--rpath -Wl,/usr/pkgsrc/devel/glibmm/wor
k/.buildlink/lib
ld: warning: libstdc++.so.5, needed by /usr/pkgsrc/devel/glibmm/work/.buildlink/
lib/libsigc-2.0.so, may conflict with libstdc++.so.6
../../glib/glibmm/.libs/libglibmm-2.4.so: undefined reference to `sigc::internal
::signal_impl::insert(std::_List_iterator<sigc::slot_base>, sigc::slot_base cons
t&)'
../../glib/glibmm/.libs/libglibmm-2.4.so: undefined reference to `sigc::internal
::signal_impl::erase(std::_List_iterator<sigc::slot_base>)'


		--Steven M. Bellovin, http://www.cs.columbia.edu/~smb