[SOLVED] PM-10PM on Zoom and in-person (Sun-Fri) 11:30AM 1:30PM (Wed, Fri)

15-213 Recitation: Data Lab Sep 13, 2021

Copyright By Assignmentchef assignmentchef

Introduction
Course Details Office Hours
Data Lab
Getting started
Running your code ANSI C
Reminders
Floating Point

Introduction
Welcome to 15-213/14-513/15-513! Recitations are for
Reviewing lectures
Discussing homework problems Interactively exploring concepts
Previewing future lecture material
Please, please ask questions!

Course Details
How do I get help?
Course website: http://cs.cmu.edu/~213
Office hours
Definitely consult the course textbook
Carefully read the assignment writeups!
All labs are submitted on Autolab.
All labs should be worked on using the shark machines.

Office Hours
6PM-10PM on Zoom and in-person (Sun-Fri) 11:30AM 1:30PM (Wed, Fri)
Queue link: https://cmqueue.xyz/ NEW LINK
Please locate the TA in the specified location: https://piazza.com/class/kr9vqwncw253c4?cid=284

OH Etiquette
Office hours are for getting ideas on how to debug or better approach your homework- conceptual OH coming soon as well so look out for that!
Please try to narrow down your problem area as much as possible to help TAs help you!
Write a description! If you dont have a description, you may be frozen/removed from the queue.
We will close the queue early so everyone can be helped by around 9:30pm so please keep this in mind!
Please find the TAs at the carrels. TAs should not need to find you

Data Lab: Getting Started
Download the handout from autolab
scp
cd to the datalab.tar file
tar -xf datalab.tar
Upload bits.c file to Autolab for submission

Data Lab: Running your code
dlc: a modified C compiler that interprets ANSI C only btest: runs your solutions on random values
bddcheck: exhaustively tests your solutions
Checks all values, formally verifying the solution driver.pl: Runs both dlc and bddcheck
Exactly matches Autolabs grading script
You will likely only need to submit once For more information, read the writeup
Available under autolab as View writeup Read the writeup please!

Data Lab: What is ANSI C?
Within two braces, all declarations must go before any expressions.
This is not ANSI C.
unsigned int foo(unsigned int x)
x = x * 2;
int y = 5;
if (x > 5) {
x = x * 3;
int z = 4;
x = x * z;
return x * y; }

Data Lab: What is ANSI C?
This is ANSI C. This is not ANSI C.
unsigned int foo(unsigned int x) unsigned int foo(unsigned int x) {{
int y = 5;
x = x * 2;
if (x > 5) {
int z = 4;
x = x * 3;
x = x * 2;
int y = 5;
if (x > 5) {
x = x * 3;
int z = 4;
x = x * z;
return x * y; return x * y; }}
x = x * z; }}

Data Lab: Reminders
Casting between int and long is ok, in either direction Be aware of operations and their types!
! returns an int even if the argument is a long
Good idea to append L suffix to every integer constant
(1L << 63) is not the same as 1 << 63(!x << 63) is not the same as ((long)!x) << 63Form Groups of 3 – 4 Series of exercises OperatorsQuestions? Remember, data lab is due this Thursday! You really should have started already! Read the lab writeup!Looking Ahead… Bomblab!!What is Bomb Lab? An exercise in reading x86-64 assembly code. A chance to practice using GDB (a debugger). x86 assembly is low level machine code. Useful for understanding security exploits or tuning performance. GDB can save you days of work in future labs (Malloc) and can be helpful long after you finish this class.Downloading Your BombHere are some highlights of the write-up: Bombs can only run on the shark machines. They fail if you run them locally or on another CMU server. Each bomb is unique – if you download a second bomb, bad things can happen! Stick to only one bomb. Bombs have six phases which get progressively harder. Make sure to read the writeup for more tips and common mistakes you might make.Detonating Your Bomb Blowing up your bomb automatically notifies Autolab Dr. Evil deducts 0.5 points each time the bomb explodes. Its very easy to prevent explosions using break points in GDB. More information on that soon. Inputting the correct string moves you to the next phase. Dont tamper with the bomb. Skipping or jumping between phases detonates the bomb. You have to solve the phases in order they are given. Finishing a phase also notifies Autolab automatically.Bomb Hints Dr. Evil may be evil, but he isnt cruel. You may assumethat functions do what their name implies i.e. phase_1() is most likely the first phase. printf() is just printf(). Ifthere is an explode_bomb() function, it would probably help to set a breakpoint there! Use the man pages for library functions. Although you can examine the assembly for snprintf(), we assure you that its easier to use the man pages ($ man snprintf) than to decipher assembly code for system calls. Most cryptic function calls youll see (e.g. callq … are also calls to C library functions. You can safely ignore the @plt as that refers to dynamic linking.S21 Bomblab Slideshttps://docs.google.com/presentation/d/1c9IVmK69sVnd zX5_rZYaL-jj5uk_d3Gl/edit?usp=sharing&ouid=1050562 71954280155624&rtpof=true&sd=true CS: assignmentchef QQ: 1823890830 Email: [email protected]