GDB watch std::string size

print ((size_t*)quit_command._M_dataplus)[-3]

https://stackoverflow.com/questions/29401095/how-do-i-access-stl-classes-like-stdstring-in-gdb-postmortem

https://stackoverflow.com/questions/16050846/how-to-use-gdb-to-watch-string-in-c

set print pretty on