What is segmentation fault?

koyi · 08-28-2003, 06:01 AM

This may sound like a stupid question but I really don't have a clue about this. Could anybody tell me what is "Segmentation Fault" actually refering to? I mean is it caused by bad memory management of the program or what?

Thanks for answering

slakmagik · 08-28-2003, 06:08 AM

Yep - a program tries to write to a segment of RAM that's already in use, which would overwrite it. So, to prevent this, I believe it's the kernel or some part or appendage of it *g*, which basically shuts the offending program down. I don't know that it's bad memory *management*, so much as bad code in the particular app making it do stupid stuff. The fact that the fault is *caught* is actually good memory management, but I could be off there.

*awaits gurus for more complete explanation*

kev82 · 08-28-2003, 06:35 AM

linux on x86 runs in something called protected mode(other platforms have similar) this allows diferent regions of memory to have access permissions, a segmentation fault is caused when you do something with a memory segement that you dont have privilages for, eg trying to jump into a non executable segment, writing to a read only segment, or going out of bounds on a segment.

in programming there are many things you could do to cause a seg fault but the most common imo are dereferencing a NULL or wild pointer.

koyi · 08-30-2003, 12:03 AM

Thanks guys! I think there is still a lot of things that I need to study about programming

HURRAH~~~!!! This is my 100th post!!!