So, one of my big pet peeves with BeOS back in the day was that it didn't seem to have a handle on the long-term ABI situation for C++. I remember it shipped with gcc 2.95 and it was stuck there. Of course BeOS mostly addressed this problem by being a catastrophic commercial failure and ceasing to exist.
But… Haiku is still around. And as I understand it, equally C++-y. Did it eventually figure out something more durable that allows people to eventually install a new compiler?