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Grex Info Item 244: Segmentation fault
Entered by brenda on Thu May 11 20:21:19 UTC 1995:

I have a program called "dikued".. it's a specialized editor.  Every
time I quit the program, I get a segmentation fault, and my stuff is
either saved or not (seems kinda random right now).

What exactly is a segmentation fault, is there anything I can do if
I get one, and how do I avoid getting one at all?

thanks

5 responses total.

#1 of 5 by brenda on Fri May 12 01:09:43 1995:

I know what the segmentation fault means now  :)

BUT... I commented out the line in my .cshrc that says:
limit coredumpsize 0

I also changed the 0 to a REALLY big number.  I still don't seem
to get a core file when I get the fault.  A friend of mine mentioned
that I might need to tell my shell to create a core file when it 
happens.  Is this true, and if it is, how do I do that?

#2 of 5 by scg on Fri May 12 02:46:55 1995:

Are seg faults and core dumps the same error messages?  I somehow didn't
think so, but it occurrs to me that I've had a limit coredumpsize 0 line
in my .logins everywhere (since I don't know how to make any sense out of
a dumped core anyway), for long enough that I haven't had any experience
with core dumps recently.

Somebody (janc, maybe?) explained seg faults to me as the computers way of
saying, "the programmer screwed up."

#3 of 5 by brenda on Fri May 12 05:24:51 1995:

Steve and Popcorn both said it was probably a bad pointer somewhere.
*I* don't have any clue about the core file, but I was hoping I could
find some nice soul who did, and who would look at it for me.

but that's just spit in the wind if I can't generate the core file
in the first place.

#4 of 5 by mdw on Sun May 21 18:59:32 1995:

These would all be better questions for the jellyware cf; very briefly;
if you can get it to misbehave consistently, your best bet would be to
run it under adb (or your favorite debugger), make the problem happen,
then use $c and other tools in adb to figure out where and why it
choked.  A knowledge of C & assembler would be helpful in terms of using
adb to learn something meaningful.

You won't get a core file if:
        you've got too small a limit on core dump sizes.
        your current directory isn't writable
        there already exists a "core" file, and the permissions
                don't permit overwriting.
        the application program has trapped the relevant signal
                and pointed it to its own error handler.

#5 of 5 by kentn on Mon May 22 23:48:36 1995:

(I get core files even with coredumpsize set to 0)
  heh.

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