Comment by jdndndb

It's more that functional languages just happen to be stricter in various ways that would've mitigated against this. You could quite happily design a functional language that has an unsafe equivalent to sscanf in its stdlib, or has big parts of the spec which are "undefined behaviour" that may differ depending on the underlying OS/compiler/runtime/stdlib in use. But the more popular functional languages have gained traction in part because they tend to have a "if you model the types correctly, the program basically works" philosophy around them. I don't think things like Haskell, Ocaml or F# would allow this if you wrote idiomatic code, you'd probably need to do something a little hacky or sketchy.

It simply would not have allowed you to write code which did that. And you wouldn't have a function like sscanf() either. You'd probably end up with a much more normal looking parser function that returned a value-or-error type.

I've never heard of a functional language that would allow you to initialize a value to whatever value the system memory already had in that memory location. In languages that allow nil, it would at least be nil; in languages that don't, you would have gotten an error about an uninitialized and undefaulted value. In any typed language, you would have also gotten an error.

It's true that C may be unique-ish in this regard though- this bug also couldn't happen in Ruby, which is not a functional language, but Ruby certainly still makes undefined behaviors much more possible than in other languages like Elixir.