Need Help Tracing a Segmentation Fault

binarybob0001 · 12-06-2007, 12:43 PM

I'm making a program that needs to be able to display a list of files. For the most part things are working. But every now and then I get a segmentation fault. I have tried tracing it by displaying messages before functions calls using cerr and the fault occurs before the functions are called. Are there any useful debugging tools for tracing a fault like this?

MicahCarrick · 12-06-2007, 01:00 PM

gdb is a pretty easy way to go. Often just running your program through gdb will give you your enough info.

However, you may need to step through it to see which call is the problem. Compile your program with -g option and run it with:

gdb myapp

Where "myapp" is the name of your executable. Then, use b within gdb to set a breakpoint. If you want, you can just do: 'b main' to set a breakpoint in main.

Use 'n' and 'si' for "Next" and "Step Into" respectively. A good gdb command reference is here: http://www.st.ewi.tudelft.nl/~koen/S...db-refcard.pdf

SciYro · 12-06-2007, 01:09 PM

Or, you can use a gdb front end such as ddd to provide a GUI.

Also, valgrind is very useful in tracking those memory problems.

MicahCarrick · 12-06-2007, 01:27 PM

Yep, good point. I've used ddd in the past and like it.

krizzz · 12-06-2007, 03:27 PM

Try Valgrind. It's a great tool, or rather set of tools for debugging as well as profiling. Much better than gdb alone as it analyzes the allocation and freeing sequences automatically which means it does the dirty job for you and reports all anomalies. Extremely useful piece of software.