Hi JP,
Yes you can use g++ to build shared libraries that labview can use. You'll want to give your C++ library a C interface. This is really common practice. You can do this by simply declaring functions as 'extern "C"'. Here is a link with more information:
http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-30.8
I've personally worked on projects that do exactly what you want to do.