The author appears to be laboring under the assumption that enabling GCC or Clang optimizations can cause failures in programs, in contrast to Java where the gu

The author appears to be laboring under the assumption that enabling GCC or Clang optimizations can cause failures in programs, in contrast to Java where the guarantees are rock solid. Of course, this is not true- in both Java and C++ the compiler's optimizations are strictly standard-compliant (at reasonable O levels in GCC) and in both if you rely on undefined behavior then optimizations can break your application. His problem isn't with unreliable optimizers, it's with writing bug-free code. And yes, HotSpot can do tons of stuff, from eliminating virtual method calls, to inlining methods, to deciding whether a wait should be busy or not. And it does become a serious pain to profile, especially when you have code paths which are infrequently hit and so might not be JITed.