Lab 7: Debugging with gdb

Introduction

In this lab you will practice using the gdb debugger.

Why you should use a debugger

When you run your program within a debugger, you can stop the program at critical points and examine the values of variables and objects. The debugger provides much more capability and flexibility than debugging a program using print statements. For example:

• The debugger allows you to examine the value of a variable after your program has crashed. Using print statements you can only see values before a program crashes.
• If you need to examine the value of a variable that you previously had not suspected, you don't have to edit, recompile and re-run your program.
• The debugger allows you to examine values of variables in the function call stack, e.g., while you are debugging a function foo(), not only can you print out the local variables of foo(), you can also print out the local variables of the function that called foo(), and the function that called that function, and so on and so forth.

In this lab, we will use gdb, a debugger with a command line interface. Although the user interface is a bit clunky, you will find that gdb has many useful features. It "understands" C and C++ types and syntax, and it works well with source code that is distributed across multiple files.