popular question : Hоw mаny linеs оf соdе is Grаnd Thеft Аutо V?

What I don't get is how they manage to efficiently debug that many lines of code ? As I've said above, I've dabbled in programming a little and I know that in C++, at least, making even the smallest mistake in writing code can lead to unpredictable behavior or the program not running at all.
I guess they gather error reports, which could more accurately point to where in the code the bug occurred, but it's still not an easy job.