Easiest way to locate a Segmentation Fault

Question

I encountered my first Segmentation Fault today (newbie programmer). After reading up on what a segmentation fault is (Thanks for all of the helpful info on this site, as well as Wikipedia's lengthy explanation), I'm trying to determine the easiest way to go about finding where my fault is occuring. It's written in C and the error is occuring on a *NIX based system (I'm not sure which one to be honest... 99% sure it's Linux). I can't exactly post my code as I have numerous files that I'm compiling that are all quite lengthy. I was just hoping for some best practices you have all observed. Thanks for your help.

P.s. I'm thinking the error is coming from dereferencing a NULL pointer or using an uninitialized pointer. However, I could definitely be wrong.

Solution 1

The easiest way is to use valgrind. It will pinpoint to the location where the invalid access occours (and other problems which didn't cause crash but were still invalid). Of course the real problem could be somewhere else in the code (eg: invalid pointer), so the next step is to check the source, and if still confused, use a debugger.

Solution 2

+1 for Tibors answer.

On larger programs or if you use additional libraries it may also be useful look at the backtrace with gdb: ftp://ftp.gnu.org/pub/old-gnu/Manuals/gdb/html_node/gdb_42.html

Comments

[netcoder]

+1 valgrind is very useful, however not much without debug flags.