Simple demonstration of lldb capabilities.
$ clang++ -Wall -std=c++1z -g ...
$ lldb a.out
(lldb) breakpoint set --file filename --line 80
(lldb) run
(lldb) s # thread step-in
(lldb) n # thread step-over
(lldb) f # thread step-out
(lldb) expr (int) variable_name
# MAGIC: will print `variable_name''s value for you!
(lldb) exit
$ _