Buffer overrun with bit-fields and value initialization - compiler bug or undefined behavior?

Question

So, I encountered a weird bug at work when I was trying to reduce the size of a struct by using bit-fields. I managed to isolate the problem and produce a minimal version that r

Answer 1

This compiler bug is being fixed in VS 2019 16.5.

As a workaround for those who cannot upgrade, consider replacing braces with regular parenthesis, eg replace S{...}; with S(...);. If no arguments are being supplied to the constructor, consider simply removing the braces as the object is still default-constructed this way.