I agree it's surprising and can only suggest the following explanations: * Undefined behaviour lets compiler developers improve the performance of certain stan

I agree it's surprising and can only suggest the following explanations: * Undefined behaviour lets compiler developers improve the performance of certain standard benchmarks (slightly but significantly) and they don't want to give that up. * Most of the people who are interested in programming language design have already deserted C/C++ so the C standards bodies are dominated by the remaining traditionalists.