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Homeworks - |
| Homework Assignments |
(Please note that access to homework assignments is restricted.)
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| Programming Assignments |
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(Please note that access to programming assignment related
information is restricted.
You should have received a password in your e-mail after you have
registered with the class mailing list.)
The programming assignments will be C/C++ code to be developed on a UNIX environment. No other programming language will be accepted and your program must compile and run with a Makefile as is on a nunki.usc.edu. You must be familiar with the UNIX development environment (vi/pico/emacs, cc/gcc or g++/cxx, make, etc.) You should use your USC accounts and preferably work on the Solaris machines in the ISD computer rooms for testing. The final (submitted) program must run on nunki.usc.edu because we are going to test it in that environment. But you should not do there the whole program development, as nunki is a general purpose server - under heavy use from many students. Late submissions will receive severe penalties. Due to clock skews, electronic submissions of homeworks assignments will be accepted within 15 minutes after the specified deadlines without penalties. If your submission is beyond the 15 minutes grace period, you will receive 75% of your grade if your submission is 15 minutes late beyond the grace period; you will receive 50% of your grade if your submission is 30 minutes late beyond the grace period; you will receive 25% of your grade if your submission is 45 minutes late beyond the grace period; and you will receive a score of zero otherwise. All submissions will be timestamped by the submission server and receipts will be issued. Whether your submission arrived to the server by the deadline is determined by the timestamp. Please keep your receipts. If a student signs up late for this class, he/she is still required to turn in all the assignments on time or he/she will receive a score of zero for these assignments. No exceptions! This requirement also applys to students on the wait list. You must follow the Electronic Submission Guidelines when you submit programming assignments. Please note that this is a brand new procedure and very different from previous procedures.
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| Modifications after Deadline |
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You are allowed to submit modifications via
e-mail to the instructor, within 24 hours
of the submission deadline.
One line (128 characters max) of change is defined as one of the following:
Afterwards, additional modifications cost 12 points per line (until 7 days past the original submission deadline). [BC: Added 1/29/2006] Please note that this applies to source code, Makefile, and README files. |
| Segmentation Faults and Bus Errors |
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I often get questions regarding segmentation faults and bus errors.
Sometimes, these occue when one calls library functions such as
gethostbyname(). Some students think this is some kind of
a networking bug. Well, it's often not. I will try to answer
this type of questions here once and for all.
Chances are that you have corrupted memory. This usually means that you have corrupted memory a while back. It just happened that when you call gethostbyname(), the corrupted memory caused a bus error or the execution of an illegal instruction. Bus errors and illegal instructions are basically the same thing as segmentation faults. How does one corrupt memory? You can write beyond an allocated memory block. You can free the same object twice. You can free an object that was not allocated. You can write to an object that's already freed. These bugs are hard to find because most of the them you only see that there is problem long time after you have corrupted memory. If you have access to a professional/expensive debugging tool, it may be helpful. Otherwise, you just need to do binary search and see where the bug(s) might be. There's no magical cures in debugging memory corruption bugs. One thing you might try is to temporarily turn off memory deallocation (if you suspect that you have freed the same object twice or freed an object that was not allocated). You can do the following to define free() as a no-op in a common header file when you are debugging:
#define DEBUGGING_MEMORY_CORRUPTION
/* comment out the above line when you are done debugging */
#ifdef DEBUGGING_MEMORY_CORRUPTION
#ifdef free
#undef free
#endif /* free */
#define free
#endif /* DEBUGGING_MEMORY_CORRUPTION */
As your code gets more and more complicated, and you are not very careful in managing your resources, you may get more of these. This is one reason why you want to keep your code nice and clean. On nunki, you can try efence. There is a copy installed in:
~csci551b/public/efence/2.2/ElectricFence-2.2.2-15
Please read:
~csci551b/public/efence/2.2/README-solaris
I have not tried this library and I do not know if it's
suitable for our programming assignments. But I've heard good things
and bad things about it. Please try it at your own risk.
Also, if you want to try this, incorporate it in your programs
as early as possible. Don't start learning it when bugs
are happening and deadlines are approaching.
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