Help with C++, gcc4.9 and libstdc++

[Fernando Apesteguía]

I maintain a port written mostly in C++ (cad/openvsp).

This port used to compile fine in 11 and 10.x in both i386 and amd64.
Since Nov 22nd I'm receiving a pkg-fallout for this port in 10.1. The
port fails with this message:

undefined reference to `__cxa_throw_bad_array_new_length'

I assume the source of the problem is defaulting to gcc 4.9 in the
ports and it seems to be related to libstdc++

I use USES=compiler:gcc-c++11-lib in the Makefile since some c++11
features are required. Any idea of why this could be failing to link?.
What puzzles me is that it compiles fine with gcc 4.9 in 10.2.

Thanks in advance.