QDBusConnectionManager destructor hangs after fork

I'm not sure if this is really a bug or just a limitation of how fork() works. This issue bite me even in the Qt 5 era and now reoccured in another use case that I was able to minimize into a following testcase: https://arrowd.name/t.cpp

When the test program is ran as

./a.out fork stuff

the program successfully terminates. However, running it as

./a.out stuff fork

makes the child hang in QDBusConnectionManager::~QDBusConnectionManager