This has got nothing to do with data races etc. but everything to do with "Sequence Points and Single Update Rule" which is well described in C language specifi

This has got nothing to do with data races etc. but everything to do with "Sequence Points and Single Update Rule" which is well described in C language specification. See my comment here - https://news.ycombinator.com/item?id=48205760 https://news.ycombinator.com/item?id=48205760