Undefined behavior is the opposite of programmer control. As the examples in the blog post show, you can write code that explicitly deferences a NULL pointer,

Undefined behavior is the opposite of programmer control. As the examples in the blog post show, you can write code that explicitly deferences a NULL pointer, or enters an infinite loop, and the compiler will think surely the programmer didn't mean to do that, and literally remove code that you wrote. It's true that historically C has not done much to protect programmers from their mistakes, but historically mistakes just meant suffering the natural consequences (such as a SIGSEGV on NULL pointer dereference). But these days, when you make a mistake, C compilers will exploit your mistake to the maximum extent possible, including changing the meaning of your programs.