1. Debuggers

2. Using a debugger • A primitive way of debugging is to insert print statements.

3. Using a debugger • A primitive way of debugging is to insert print statements. • That’s OK but a debugger is much more powerful. • It’s a program that watches and controls another program as it runs!

4. Using a debugger • A primitive way of debugging is to insert print statements. • That’s OK but a debugger is much more powerful. • It’s a program that watches and controls another program as it runs! • It allows us to execute our code one line at a time. • It allows us to set breakpoints (stop points) in our code. • We can even examine and change the contents of variables as our program runs!

5. jgrasp

6. Setting a breakpoint (jGRASP)

7. Breakpoint is now set (jGRASP)

8. Start the debugger (jGRASP) • Build -> Debug • The program then runs and stops at our first breakpoint.

9. step over step in step out jGRASP variables (r-click to change value) next line to be executed end debugging

10. VC++

11. Setting a breakpoint (VC++)

12. Starting the debugger (VC++)

13. Watch variables (VC++)

14. VC++ debugging options

15. gdb

16. Debugging with gdb (Unix/Linux) • Direct compiler to include debugging information with –g (ex. g++ -g test.cpp) • Run the debugger and indicate program to debug (ex. gdb ./a.out)

17. Setting a breakpoint (gdb) in main and start running

18. Print and set (change) var

19. List source code

20. Useful gdb commands • b main set breakpoint in func main • b 10 set breakpoint at line #10 • cont continue • del break delete all breakpoints • l (ell) list source code lines • l <func> (ell) list source code lines for <func> • n next (like step over) • p <var> print contents of variable • quit end execution • run start running program • s step (like step into) • set <var>=value change var