Programming

I'm trying generate an interrupt every 1 seconds using itimer and My clock is not running. This is what i did :

printf("about to sleep for 1 second \n");

signal(SIGALRM, wakeup);

//myTimer.it_interval.tv_sec=0;
//myTimer.it_interval.tv_usec =0;

myTimer.it_value.tv_sec = delay;
myTimer.it_value.tv_usec =0;

setitimer(ITIMER_REAL, &myTimer, );


Can anyone give me some idea how to debug my program ? and are there any good reference book i can read. Thanks

Heres a good reference on alarms and timers using interrupts:

http://www.gnu.org/manual/glibc-2.0..../libc_306.html

Posting a couple of lines from a c program is not enough to do any good.

The only debugging tool that I ever use is to insert a printf statement at strategic points in my program to see what's happening. It's low tech, I know. But it actually works very well.

Me too. But occasionally and to find out where a segmentation fault occurs I use gdb.

There is an official GDB manual, but usually I simply use the command-line help to view the help info of gdb commands.

Further to what Perderabo said, I use a form of printf to debug my programs.

Rather than displaying messages to screen, I would write those same messages to a log file.

This could obviously mean a very large file, which will mean a performance degredation, so the logging (or tracing) is conditional on a configuration setting being activiated e.g. an environment variable or in an configuration (or ini) file or a flag on a database table.

A trace level could also be defined e.g. 9 for most detailed to 1 for the least detail.

Although creating a mechanism to log to a file will require more programming effort, it will be invaluable to you if you have developed your program and delivered it to a 'live' system where your development tools won't be available. You may not be able to predict when your fault is going to happen either, especially with background or daemon processes.

After you have put in the effort to create your new logging functions, you may want to encapsulate them into a library for use in future projects. To this end I believe many Unix systems will provide standard functions to allow you to write messages to the system log if you prefer.

Whether you are logging to a file or the screen or even using a debugger I would recommend you track the following features of your program:

1. When a function is called
2. When a function exits.
3. The input values, or paramters to functions
4. The return values, or parameters of functions
5. When a variable is first assigned.
6 When a variable changes

(Be sure to display all strings within quotes so you can see any whitespace in the string)

This should allow you to tackle most faults in your program.

MBB

It's probably a better idea to use fprintf(stderr, ... ) so that any errors are IMMEDIATELY reported. Otherwise, your program may die before the stdout buffer makes it to the screen. I've had this happen MANY times where the last debugging line on the screen did NOT indicate where the program REALLY died. Either use stderr or use fflush() after writing to a log file.