debuggers for c + threads

Hi i have recently installed gdb and ddd debugger.... I need to debug my program that all the time returns segmentation fault
My problem is that i dont know how to debug a program with multple files and with multiple threads.. I think the segmentaion fault occurs when the threads exhcange data between them... I will need something that can read concurrently lot of sources and let me put inside some breakpoints...
Can u help me with this ?

make sure your program has been compiled with the -ggdb flag

run ddd ./your_program

Then goto File/Open Source

It should present a list of source files used in your program.
Choose the one in question.

Go to the line you would like to set your breakpoint at and right-click on the margin.

Choose Set Breakpoint.

Click the Run button.

This is pretty self explainatory I believe.

Thx a lot for your help I ll try it and i ll ask u again