On Undefined Behavior

Question

Generally, UB is regarded as being something that has to be avoided, and the current C standard itself lists quite a few examples in appendix J.

However, there are c

Answer 1

If you know for a fact that your code will only be targeting a specific architecture, compiler, and OS, and you know how the undefined behavior works (and that that won't change), then it's not inherently wrong to use it occasionally. In your example, I think I can tell what's going to happen as well.

However, UB is rarely a preferred solution. If there's a cleaner way, use it. Using undefined behavior should really never be absolutely necessary, but it might be convenient in a few cases. Never rely on it. And as always, comment your code if you ever rely on UB.

And please, don't ever publish code that relies on undefined behavior, because it'll just end up blowing up in someone's face when they compile it on a system with a different implementation than the one that you relied on.