I just read this link. Now I know why i = i++ is an UB.
But I don't know why ++++i is an UB too.
For example,
int i = 2;
++++i;
I think the value of i should be 4. Isn't this a defined behavior? (I'm talking about C++98 and C++03)
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Then don't tag C. It's not UB, it's simply ill-formed in C. – StoryTeller - Unslander Monica Mar 07 '18 at 07:57
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@StoryTeller: I *thought* (and I do seem to be dreaming a lot these days), `++++i` was UB up to and not including C++11. – Bathsheba Mar 07 '18 at 08:06
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2@Bathsheba - It was. But `++i` is not an lvalue in C. So we don't reach UB, as a compiler error hits us in the face. – StoryTeller - Unslander Monica Mar 07 '18 at 08:08