1. YongChul Kwon yongchul@cs
CSE451 Section 1: Spring 2006
YongChul Kwon

2. Reminders Sign up for mailing list Read the web site
Start reading the book
Homework due Monday
Read & start project 0
Project 0 due Tuesday
Check access to
forkbomb.cs.washington.edu

3. More administrative infomation
Office hour
Prof. John Zahorjan
Wed 3:30 – CSE534
YongChul Kwon
Mon & Thr CSE216
By appointment
Kurtis Heimerl
Mon & Wed & Fri CSExxx

4. CSE451 projects <=5 interesting & challenging projects
Practice C & UNIX
Shell & process control
User-level threads
Virtual memory trace analysis
File systems
Likely to be the same as past

5. Resources Use ‘forkbomb.cs.washington.edu’! VMware machines in 006
Well-managed(?) sandbox
Do not disturb other students
VMware machines in 006
Only for the final project
Will distribute image for VMware player®

6. Advices Start early Read & code thoroughly Use tools It is HARD!
Top-down
From Big picture to details
Use tools
Editors, debuggers, compiler, shell, …
Pencil & paper

7. Project 0
C programming warm-up

8. C Remember what you did in CSE303 Do you remember
I know it is a painful memory…
Do you remember
Pointer & pointer arithmetic
Stack & heap
User defined data type
Preprocessor
String manipulation
Standard C library

9. New in this course System call Union Function pointer % man 3 strcpy
% man 3 fopen
% man 2 open
Union
Function pointer
What is a function?
How is it stored in binary?
How is it mapped into memory?
What is a function pointer?

10. Example

11. Poll How do you “debug” your program?
Print, print, print, print, print, …
Stare & spot
Ask friends
Use debugger
Other

12. GDB Most frequent GDB commands
Execution: run, continue, step, next
Browsing stack: up, down, backtrace
Investigate data: display, print
Break point: break, clear, condition
Browsing source: list
Don’t forget to specify ‘-g’ when you compile

13. Debugging relevant on later projects
This slide is borrowed from section 1 in Winter 2006
In C99
#ifdef DEBUG
# ifdef __KERNEL__
/* This one if debugging is on, and kernel space */
# define PDEBUG(...) printk(__VA_ARGS__)
# else
/* This one for user space */
# define PDEBUG(...) fprintf(stderr, __VA_ARGS__)
# endif
#else
# define PDEBUG(...) /* not debugging: nothing */
#endif
Usage
PDEBUG(“Num1 : %d, Num2 : %do numbers: %d and %d\n”, num, num2);
Don’t forget to declare DEBUG to enable

14. Write a safe code What is the problem of following code?
char *buf = (char *)malloc(32);
strcpy(buf, argv[1]);
How can we fix it?

15. Probable errors Why do we get segmentation fault?
Why do we get bus error?
Do we have to write memory-leak-free program? Why?
Operating system
Web server
Shell
Homework