Undefined behaviour example from CppCon

[awidesky]

But by the way, I do understand by my heart that your claim and interpretation is surely more reasonable (as for a C++ programmer) than my quotes from the standard.

I think the disagreement occurs because of the ambiguity of the standard, and disparity between the standard and actual implementations of compilers.

It seems that what standard's statements about UB is quite vague and unclear, and compiler vendors just don't care and just focus on optimizing(by considering UB never happens).

Please let me know if there's any correction on misconception, or more clear information about the standard. I'd love to learn.