It exists, but it doesn't do anything in the example that was discussed recently, "undefined behavior may call a never-called function": https://news.ycombinato

It exists, but it doesn't do anything in the example that was discussed recently, "undefined behavior may call a never-called function": https://news.ycombinator.com/item?id=15324414 https://news.ycombinator.com/item?id=15324414 As far as I can tell, -O0 is the only way to avoid that particular mis-optimization in Clang.