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For this assignment, you will be practicing with the basics
of gdb. You will want to use gdb extensively during the rest
of the semester, as it is an incredibly useful tool to gather
information during the debugging process. For now, we
are just going to get started with some basic commands.
Be sure you have done the readings and watched
the video on gdb.
Enclosed, you will find game.c and the compiled
binary game, for the most boring guessing game
ever. In the first round, the program thinks
of a secret number (it is the same every single time),
and asks you to guess it. You get exactly one try.
Note that it thinks of this number by calling
getSecretNumber, which is not included in the source.
If you get that right, in the second round,
it thinks of another number. It does this by repeatedly
calling getOtherSN (also not shown in the source) and
passing in different numbers. It combines these results
together, and does some math to combine the results into
"total". Afterwards, it asks you for your guess,
and again, you have one chance.
Before you proceed, try to "play" the game once by running:
./game
For example, I ran it and guessed 4:
$ ./game
I'm thinking of a number...
What number do you guess?
4
I'm sorry, that is not right. You lose
It would be pretty boring to play this game
until you actually guess the right number and win,
but fortunately, that isn't the point. The
point is to practice with gdb.
In emacs, do
ESC-x gdb
Emacs will prompt you for how to run gdb (the default should be fine),
and then give you the gdb prompt.
Use the "start" commmand to begin execution, then use "next"
and "print" to find the secret number for round 1.
When the program prompts you for this number, you should be able
to guess the right one from the information you gathered.
For round 2, you do not want to step through 5000+ iterations of the
loop, so set a breakpoint after the loop, continue execution until you
reach it, and the print out the variable "total". Now you should
be able to win round 2 instantly as well!
Once you have found the two secret numbers, create a file called input.txt
and place them in that file, one per line (round 1's secret number
on the first line, and round 2's on the second line).
You should be able to run
./game < input.txt
and "win" automatically. That is, you should see this output (without
having to type anything else):
$ ./game < input.txt
I'm thinking of a number...
What number do you guess?
Correct! You win round1!
Ok, time for round 2. I have another secret number.
Your guess:
You win round 2 also!
When you finish, add input.txt to git, then commit, push, and grade.
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