Although it is trivial, there is enough in our Zoo program to try out the debugger. If you want to follow along, then build the program from scratch with:-
g++ -g -o Zoo.exe *.cpp Zoo.cc
and then run the debugger:-
gdb Zoo.exe
Set a breakpoint at the start of the program and start running the program:-
break main run
when the debugger stops it will show you the current line that it is about to execute. Type
list
to look at the lines about the source line. Now type
next
repeatedly (actually you only need to type it once - after that just press RETURN to repeat the last command) to watch the top level program execution.
When it finishes type:-
run
again. The debugger will ask for confirmation as there is already a program running so type 'y' to confirm. This time, when it stops at the start of the program type:-
break Human::Talk cont
This sets a breakpoint at the start of the function Human::Talk
and then continues execution until this breakpoint is reached. Type:-
info stack
to see the function calls that lead to this point. Now type:-
print this
to look at the current object pointer. It will just tell that it is
a pointer to Human. If you want to print out the contents of
the current object type:-
print *this
In this case the output looks rather complicated because the
Human object contains some complicated STL string objects and
they are get printed too.
To look at something simpler, try:-
print fAge
to check on the Human's age and finally:-
set fAge = 50 cont
to modify the age and resume execution. Now type:-
quit
to leave the debugger.