I am not comfortable releasing a version of MacPorts that includes a MacPorts gcc in the default compiler list (which 2.4.3 now does) without having answered the new-vs-old ABI question satisfactorily. I believe releasing that will lead to the libstdc++ mismatch crashes that were the reason why we previously strongly prohibited the use of MacPorts gcc for C++ code:
https://lists.macports.org/pipermail/macports-dev/2018-March/037829.html I had hoped Jeremy H would weigh in, but I don't think he has yet. Or did we reach a consensus on how we would handle this, and I've forgotten?