Null References, the Billion Dollar Mistake

jonr writes "'I call it my billion-dollar mistake. It was the invention of the null reference in 1965. At that time, I was designing the first comprehensive type system for references in an object oriented language (ALGOL W). My goal was to ensure that all use of references should be absolutely safe, with checking performed automatically by the compiler. But I couldn't resist the temptation to put in a null reference, simply because it was so easy to implement. This has led to innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years. In recent years, a number of program analysers like PREfix and PREfast in Microsoft have been used to check references, and give warnings if there is a risk they may be non-null. More recent programming languages like Spec# have introduced declarations for non-null references. This is the solution, which I rejected in 1965.' This is an abstract from Tony Hoare Presentation on QCon. I'm raised on C-style programming languages, and have always used null pointers/references, but I am having trouble of grokking null-reference free language. Is there a good reading out there that explains this?"

Comments

Re:There was a bigger mistake:

[Anthony_Cargile]

Null-terminated strings. The bane of modern computing.

Maybe I'm feeding a troll, but what else would you terminate it with without using something the string may contain? Keep in mind that null-terminated strings were, err, "invented" around the time ASCII was really the only fully widespread character standard, and something was needed to mark the end of a string for detection by software.

The mistakes you speak of are made by programmers that don't know how to securely utilize this in certain environments. Mainly in buffers, but recall the lkml thread about the license macro in kernel modules being abused with '\0'.