The problem is so much worse than that. Combining even the most fundamental features of the language (like UB and concurrency) leads to dark corners where even

The problem is so much worse than that. Combining even the most fundamental features of the language (like UB and concurrency) leads to dark corners where even experts like Boehm aren't sure. The recent TR about safety-critical C++ is basically "don't use C++", which is correct, but not particularly helpful. The reality is that the standard simply isn't a good enough reference for what the language does. If you care about that, you need to treat programming in it as an experimental endeavor where you validate that your particular combination of code + toolchain + hardware does what you want. It's nice if the standard goes along for the ride, but not something you can rely on.