On: So you think you know C? (2016)

[flowerlad]

“I don’t know” is not the right answer. I do know. I know the answer to be “Unspecified”.

[thayne → flowerlad]

But you _don't_ know what it returns, because the behavior is either undefined or implementation defined, and you don't know the implementation.

[ben509 → thayne]

But you do know that it's undefined or implementation defined. It's a "known unknown".

[Thorrez → ben509]

Yes, so you knowingly click "I don't know". You don't know the value, and you know that you don't know the value.

[H8crilA → ben509]

Look, do you know what will it return or not?

[saagarjha → H8crilA]

Not without knowing the compiler, which I think was the point.