Lab 6: C++ Debugging Lab: Working with the VSCode Debugger

Instructions

• First read this page then start working on lab with the GitHub classroom link below.

• Put your code in the GitHub repository for this lab.

• After you complete the lab, answer the questions in the README.md file. Enter your answers directly in the README.md file.

• Github Classroom Link: https://classroom.github.com/a/xylMar4l

Objective

Familiarize yourself with the essential features of the VSCode Debugger while working with a C++ programs.

Debugging - Part 1

• Setup:
  • Open the file ecommerce.cpp in the Part1 directory in the repository.
• Setting Breakpoints:
  • Set a breakpoint at the start of the main function.
  • Set another breakpoint inside the processOrder function.
  • Add a third breakpoint in the applyDiscount function.
• Start Debugging:
  • Launch the debugger. First click the debug icon in the activity bar on the left. Then click the “Run and Debug” button.
• Stepping Through the Code:
  • When the debugger pauses at main, press “Step Over” until you get to the processOrder function call.
  • Now, press “Step Into” to dive into the processOrder function.
  • Inside the processOrder function, you’ll soon see the applyDiscount function call. First, press “Step Over” to notice how you skip the internals of applyDiscount and directly get its return value.
  • Run the processOrder function again. This time, when you’re at applyDiscount, press “Step Into” to go inside it and inspect its inner workings.
• Observing the Call Stack:
  • Inside the applyDiscount function, take a moment to observe the CALL STACK pane. You should see the function hierarchy: applyDiscount called from processOrder which was called from main.
• Modifying Variables & Stepping Out:
  • In the applyDiscount function, under the VARIABLES section, change the value of user to “Jane Doe”.
  • After making this change, press “Step Out” to move back to the processOrder function and observe how the change impacts the total cost.
• Completing Execution:
  • Press “Continue” to complete the program.
  • Expected Output:

      Total Cost for John Doe: $50.99
    

  • Note: If the user was changed to “Jane Doe” during debugging, the discount wouldn’t be applied, and the total cost would be $55.99.

Debugging - Part 2

• Setup:
  • Open the file Student.cpp in the Part2 directory in the repository.
• Setting Breakpoints:
  • Set breakpoints inside the read_students_from_file function and inside the catch block in the main function.
• Start Debugging:
  • Start debugging.
  • As the debugger stops at the breakpoint, inspect:
    • The state of the file object to ensure the file has been read correctly.
    • The values of the name and age variables.
    • The contents of the students vector after reading from the file.
• Debugging with Error Handling:
  • Intentionally introduce an error by renaming the students.txt file to students_renamed.txt.
  • Debug the program again. This time, the debugger should stop inside the catch block.
  • Inspect the thrown exception’s message by examining the ex variable.
  • Fix the error by renaming the file back to students.txt or updating the filename in the code.
• Enhance the Student class:
  • Add more attributes, such as grade or major.
  • Modify the file I/O functions accordingly and use the debugger to ensure everything works as expected.
  • Introduce a few more intentional errors or exceptions and practice using the debugger to catch and understand them.

Debugging - Part 3

• Setup:
  • Open the file factorial.cpp in the Part3 directory in the repository.
• Setting Breakpoints:
  • Set a breakpoint inside the factorial function.
• Start Debugging:
  • Launch the debugger.
  • As the debugger stops at the breakpoint:
    • Inspect Variables: Hover over the variable n to observe its value during each recursive call.
    • Step Through the Code: Use the step-over and step-into buttons to navigate through the recursive calls.
  • Try to identify the reason why the recursion never terminates.
• Fixing the Recursive Function:
  • Once you’ve identified the missing base case, modify the factorial function to include a termination condition for the recursion.
  • Debug the program again to ensure the recursive function now works correctly.
  • Expected Output:

      Factorial of 10 is: 3628800
    

• Now try:
  • Modifying the input value (number) to larger values and see how high you can go before running into potential issues.
  • Observe how the call stack grows with larger input values.
  • Introduce other recursive functions, like the Fibonacci sequence, and practice debugging them.