EECS 183 Labs

EECS 183 Lab 2: Functions and Debugging

Lab due on your scheduled lab day (Jan 17-23)

Lab accepted for full credit until Tuesday, January 24, 2023, 11:59 pm Eastern

Google form for Debugit direct submission link

Debug the code autograder direct submission link

In this lab, you are writing code and solving practice exam questions to master the use of functions, and to learn a new resource for finding bugs in your programs.

By completing this lab assignment, you will learn:

To understand how to call and use functions.
To be able to use the debugging functionality of your IDE to understand how the code you write is executed.
To promote the use of this debugging functionality when completing your projects.
To practice writing answers to exam questions and receive early self-assessment of preparedness for the exams.

Requirements

You should complete this lab in small groups of about 4 students.

IMPORTANT: For all labs in EECS 183, to receive a grade, every student must individually submit the Lab Submission.

Create a project using the debugit.cpp from the starter files, shown below.
Head to the Google form for Debugit here while signed into Google with your own @umich account and follow on-screen instructions while using the debugger.
Create a second project using the lab2.cpp from the starter files, shown below.
Modify the lab2.cpp starter file with your solution to the lab with your peer group in the Lab Assignment.
Submit your debugged lab2.cpp file to the autograder here

NOTE: Your lab 2 assignment grade will require both submissions for full credit.

Starter Files

You can download the starter files using this link.

The IDE setup tutorials for Visual Studio and XCode include a video about how to set up a project using the starter files. You can access the tutorials here:

Lab Assignment

Debugit

5 Points of 10 total for Lab 2 assignment grade

One primary tool that saves your time developing and testing is a debugger. Debuggers are simple to use, and run your code line-by-line as a computer sees it. Bugs that would take hours to find by hand can be found in a few minutes with a debugger. Debuggers help you find why and where your code is incorrect. The key to debugging is setting breakpoints, investigating variables, watching variables, step into, step out of, and step over. That’s about all the EECS 183 staff use and it can save hours of work. So we will teach you how to use a debugger with this exercise.

Create a new project in Xcode or in Visual Studio. If you don’t quite remember how to do that, take another look at the Starter Files Section above.
Okay, so now that you have a new project, add debugIt.cpp to your project from the Starter Files. Make sure not to change any code in this file, and do not add the lab2.cpp file to this project! The code in debugIt.cpp is “obfuscated” and does not demonstrate the best style practices, mostly to encourage you to use a debugger to find answers, instead of figuring them out by hand.
Don’t forget to delete main.cpp (if you are using Xcode). Otherwise you will get a build error.
Now that you have the source code in your IDE, proceed! Without worrying about what the code in debugIt.cpp is supposed to do, head to the Google form for Debugit here while signed into Google with your own @umich account and follow on-screen instructions. Type your answers in the form.
You can get the return value of a function by first stepping into it and then stepping out of it.
Once you have submitted the form, you are done with DebugIt. You can come back, edit your responses and resubmit before the due date and time.

IMPORTANT: For all labs in EECS 183, to receive a grade, every student must individually submit the Lab. Late submission for Labs will not be accepted for credit.

How to Submit Debugit

During the exercise, you should follow along in the Google form above while using the debugger in your IDE. Be sure to submit the Google form when you are done. You should receive a confirmation email to your @umich email address when you have successfully submitted the form.

Debugging the Code

Now that you are familiar with the basic operations of the debugger, you can practice your new skills with buggy code. In this part of the assignment, you will start with a program that has several bugs. Use the debugger to find the bugs in the program and rewrite the code to eliminate the bugs.

NOTE: In fixing the bugs, you must not change the parameters for the given functions! The autograder will give you a score of zero if you do. This is the case for all Projects 1-4 in EECS 183. There are no compile errors in the code, only bugs that result in incorrect output.

Create a new project in Xcode or in Visual Studio. If you don’t quite remember how to do that, take another look at the Starter Files Section above.
Okay, so now that you have a new project, add lab2.cpp to your project from the Starter Files. Do not add the debugIt.cpp file to this project!
Set a breakpoint at the statement to call the function feedPet() in the main() function.

// set your first breakpoint on the following line
int newHunger = feedPet(careForPet, hunger);

Run the project. For input examples, see the Sample Runs Section below. The output of the buggy program will not match the Sample Run.
When the program stops at the breakpoint, use step into to follow the function call. Check the values for the parameters hunger and food. Are these values what you expected? If not, what could be the cause of the values not being as expected? You should be viewing the Locals window to see the values of the local variables for a function.

HINT: Look carefully at the values for hunger and food in the feedPet() function. This is your first bug to find. Remember, you cannot change the parameters for the functions you are given so you must instead change the statement in main() where this function was called!

Now, step over the statments until you are just about to execute the return statement, return hunger;. Is this the correct value? Check the RME (Requires, Modifies, Effects) comment at the top of the function. What does the Effects say?

HINT: Look carefully at the Effects of the RME and the variables and operators used in the feedPet() function. This is your next set of bugs to find. The use of the hunger and newHungervariables is not correct. What should the assignment operation be to the newHunger variable? Which variable should be used in the return statement?

When ready, step over the return statement, which will take your debugger back to the main() function statement where feedPet() was called. In the Locals window of the deubgger, you can see the values for all of the variables in the main() function along with the value returned by the feedPet() function.
Continue to step over statements, being sure to step into the statements with function calls. Check the values of variables to find where the statements are buggy.
Update your program until the inputs shown in the Sample Runs below match between the specification and your debugged program.
Submit to the autograder to see if you found all of the bugs!

Sample Runs

Sample Run 1

TamagotchEECS Pet Simulator
Please enter pet name: Grumpy Cat
Please enter pet initial hunger: 100
Please enter pet initial happiness: -50
Please enter number to be used for feeding and petting: 50
After caring for Grumpy Cat, current hunger is: 50 and happiness is: 0
Thanks for using TamagotchEECS Pet Simulator! Good luck!

Sample Run 2

TamagotchEECS Pet Simulator
Please enter pet name: Taco
Please enter pet initial hunger: 500
Please enter pet initial happiness: 77
Please enter number to be used for feeding and petting: 42
After caring for Taco, current hunger is: 458 and happiness is: 119
Thanks for using TamagotchEECS Pet Simulator! Good luck!

Sample Run 3

TamagotchEECS Pet Simulator
Please enter pet name: Jabba
Please enter pet initial hunger: 7000
Please enter pet initial happiness: 100
Please enter number to be used for feeding and petting: -250
After caring for Jabba, current hunger is: 7250 and happiness is: -150
Thanks for using TamagotchEECS Pet Simulator! Good luck!

Sample Run 4

TamagotchEECS Pet Simulator
Please enter pet name: Punxsatawny Phil
Please enter pet initial hunger: 42
Please enter pet initial happiness: 42
Please enter number to be used for feeding and petting: 42
After caring for Punxsatawny Phil, current hunger is: 0 and happiness is: 84
Thanks for using TamagotchEECS Pet Simulator! Good luck!

How to Submit Debugging the Code

When ready to submit to the autograder, visit https://autograder.io/web/project/1857. You will submit your lab2.cpp file which should contain your solution for this lab as one program.
Drag and drop your completed lab2.cpp file to the box labeled Drop files here or select Choose file and navigate to your file. The file you submit to the autograder MUST be called lab2.cpp.

Note: If you’re using Xcode and don’t know how where exactly lab2.cpp is located on your disk, right-click (or click while holding down the Control key) on the file in the Navigator area on the left side of the Xcode window and choose Show in Finder.

If you’re using Visual Studio and would like to know where lab2.cpp is on your disk, right-click on lab2.cpp in the tab above the Code pane and choose Open Containing Folder.

If confident that you’ve selected the correct file, click Submit to submit to the autograder. The autograder will tell you if you did not select a file of the correct name. We strong urge you NOT to hit submit, but choose the correct file instead.

IMPORTANT: Late submission for Labs will not be accepted for credit.

For all projects and labs in the course, we grade your highest submission score. In future projects you will receive a limited number of submissions with feedback per day.

In projects in courses at Michigan, you receive very limited submissions with feedback per day, typically four times per day. However, for this lab, you will receive ten submissions per day with feedback. Once you receive a grade of 5 of 5 points for lab2.cpp from the autograder you will have received full credit for this lab.

Autograder Feedback

You can see the grade and feedback from your submissions by selecting My Submissions in the upper-left corner. Selecting a submission from the left tab will show the tests and feedback for the lab. When your submissions fail one or more tests, feedback about the test will be displayed. The autograder will show a line-by-line difference between the exepcted output for a correct solution and the output of your program.

IMPORTANT: Differences in blank lines will not cause your program to fail tests for this lab. There must be another reason for the test to fail, look closer.