pop_back() implementations have checks, but they're opt-in (and how to opt-in is specific to each implementation). This is just how C++ works: performance over

pop_back() implementations have checks, but they're opt-in (and how to opt-in is specific to each implementation). This is just how C++ works: performance over safety, safety is semi-possible but requires a bunch of opt-ins. And the parts needed for safe C++ aren't standardized, so good luck if you're using multiple compilers.