segmentation fault
 

Can anyone please explain to me the following strange phenomenon?

I have a code in C, and when I compile it is Windows Platform compiler (Borland 5.5), they compiling is fine and when I execute the program, everything turns out ok.

However, when I use the same code and compile it in UNIX, the compiling is ok but when I execute the program I get a "Segmentation fault" message?

Re: segmentation fault
 

There is a bug in the code. You are fortunate that the UNIX platform at least shows you this; in Windows it is just "lucky" to be running.

Re: segmentation fault
 

How is that strange? On Windows you didn't touch memory that would cause a critical error, on Unix you did. It means your code is broken. Look for uninitialized pointers and out of bound array accesses. Those are the prime culprits for a seg fault.

Re: segmentation fault
 

if there is a bug in the code, why doesn't it show when I compile?
how can i rectify the problem?
I thought segmentation fault has got to do with memory errors...
or is this a portability issue?

Re: segmentation fault
 

>if there is a bug in the code, why doesn't it show when I compile?
*stunned silence*

>how can i rectify the problem?
Take my suggestions and look for off by one errors when you index an array or places you might have an uninitialized pointer.

>I thought segmentation fault has got to do with memory errors...
Yes. If you access memory outside of your address space, you get a segmentation fault.

>or is this a portability issue?
No, it's a programmer issue. Fix your broken code.

Re: segmentation fault
 

Yes, segmentation fault has chased me long enough when i was learning pointers. Most of the time it gotta do something with the pointers or array. It occurs when...

1. U de-reference a NULL pointer.
2. U de-reference an uninitialized pointer --which results in accessing memory outside of ur memory space.
3. Indexing an array where the index is out of the arrays boundary---- which also means accessing not permitted memory space.
That are the three reasons i can rem for now.

As far as i know the program should have crashed in Windows pc if it were the first case. Since it works with windows itz perhaps either the second or the third case. Look for array bounds, especially in Loops.

Re: segmentation fault
 

I have been trying to find out where the bug is but so far I have no luck.
Is it possible to have segmentation fault when the system "run out of memory"?

Re: segmentation fault
 

It depends on what you mean by "run out of memory". If malloc fails then it returns a null pointer, which would cause a seg fault if you don't test for failure. However, malloc failure is extremely unlikely these days, so the problem is still probably something you did wrong. If running out of "stack" space for automatic variables caused a segmentation fault, I would still be suspicious of your code because Unix is very good about growing the "stack" if needed. So if you're actually running out of memory (meaning fast memory and virtual memory), there's a lot more wrong with your code than a little error.

Unfortunately, memory errors are very difficult to find, and without actual code to look at, we're just making educated guesses.

Re: segmentation fault
 

Hello,

Please post your code. Let's take a look at it. Please use CODE tags when you do it, so that it is nice and clean to read.

Christian