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Thanks for pointing that out. Detecting UB is hard and sometimes impossible in C and C++. If you design your language accordingly you can avoid that. At least I

• coliveira 3y ago
  If some form of UB is impossible to detect, then the compiler cannot do anything about it either, making the whole debate useless. Any action taken by a compiler relating to UB must be for some cause that is detectable at compilation time.
  • layer8 3y ago
    That’s not quite true, the compiler could add code to detect all UB at runtime, and then abort or whatever. It’s just that this would also pessimize UB-free code, and most compilers opt to not do that, at least in release mode.
  • weinzierl 3y ago
    That is not true and very important to understand. The optimizations a compiler does by eliding UB stuff are often very effective and I think no one in the thread has questioned that. It is a fallacy, though, to think that these optimizations could be replaced by diagnostics. That would be hard in most cases and sometimes impossible.