[reza_n]

I would argue the opposite, assert() statements are the best way to write defensive and secure C. There might have been a time when people commonly compiled out assert() statements from binaries, but that is only OK if the software was designed for that. Otherwise, that would be like me saying I am going to compile out all strlen() statements from a given binary and then expect it to behave the same.

[irundebian]

Secure code should be correct and robust. To assure correctness assert()'s should be used, to assure robustness you should check return values and buffer sizes.