AVR-8 doesn't have a hardware/interrupt mechanism to support assertion. Well, you can skip the assertions if you safely can because all the assert() are replaced with ((void)0), but if you want to do something about it then,
1. Define the ASSERTUSESTDERR symbol.
1. Make sure the assert funcion is called without parameters, Like assert(NULL).
1. Write a function with the following signature
extern void _assert(const char *func, const char *file,
int _lineno, const char *sexp)
//Do what you want to do, may be
Reference : http://www.nongnu.org/avr-libc/user-manual/groupavrassert.html