Its been awhile since I C++'ed heavily, but I think this isn't quite right:

"But even there, the code (most likely) dereferences a pointer one past the end of an array, which is (1) invalid C++ and (2) not on their list of possible bugs."

There's a weirdo thing with array allocation in C++ at least which makes it valid to use arrays with all of the std:: algorithms that take a start and end parameter. Unfortunately I can't remember it well enough to find a good reference but as I recall it was more than just a pointer comparison as the std:: algorithms wanted to be able to dereference it occasionally.

Then again its been about four years since I've touched C++ so some of these details have leaked out and gotten mixed up.