i have a problem when i debug my program

i have a problem when i debug a program.

when i use the order nios-debug *.out,it gives me a warning:progrm received signal SIGTRAP,Trace/breakpoint trap.

i do not know what does this info mean?

the development kits i use is nios+apex20k200

if you have met this problem,please tell me how to solve it.thank you very very much!