3 ms·

Who would you rather trust to do bounds checking, computers who are zealously good at doing what they are told to do to the point of absurdity or humans who are

Who would you rather trust to do bounds checking, computers who are zealously good at doing what they are told to do to the point of absurdity or humans who are notoriously bad at following rigorous procedures? I mean, we've seen from several other fields that the only way to get the safety standards of human procedures up is to introduce checklists and get people to rigorously follow them [1]. If you want to elide bounds checks for performance reasons, which is easier: manually verifying for yourself that every single array access is guarded by a bounds check somewhere and ensuring that no subsequent code changes break this verification, or getting the compiler to prove for you that every bounds check can be safely elided? [1] And of course we still have several issues in fields like medicine where practitioners refuse to adopt this methodology because they find checklists to be an insult to their intelligence.

bayindirh 3y ago
> getting the compiler to prove for you that every bounds check can be safely elided? I'd prefer to delegate that where compiler if it can do that for that piece of code at hand. I've written about a case where it'd be very hard for a compiler to eliminate a bounds check because the guarantees are made elsewhere in the code. On the other hand, I'd rather add my bounds check voluntarily (it's very simple in C++ vectors for example. use ".at()" instead of "[]", that's all), because I generally design my code in a way which doesn't need bounds checks by failing hard and early at places where I build/fill the arrays/vectors and prone to malformation. So, you need to be well-formed to pass these checks, and these data structures are not modified ever down the pipe. If they are modified, they'll be bound checked of course. What I'm saying is, I'm not naive enough to believe that I'm perfect, but I'm not naive enough to believe that compiler is perfect, either. So, I do my part, and leave the parts I can't be sure to the compiler. I'm not an hard-liner. I just want finer control on my code, and take full responsibility if it crashes and burns in a way it shouldn't, so plan and implement accordingly.

bayindirh 3y ago

> getting the compiler to prove for you that every bounds check can be safely elided? I'd prefer to delegate that where compiler if it can do that for that piece of code at hand. I've written about a case where it'd be very hard for a compiler to eliminate a bounds check because the guarantees are made elsewhere in the code. On the other hand, I'd rather add my bounds check voluntarily (it's very simple in C++ vectors for example. use ".at()" instead of "[]", that's all), because I generally design my code in a way which doesn't need bounds checks by failing hard and early at places where I build/fill the arrays/vectors and prone to malformation. So, you need to be well-formed to pass these checks, and these data structures are not modified ever down the pipe. If they are modified, they'll be bound checked of course. What I'm saying is, I'm not naive enough to believe that I'm perfect, but I'm not naive enough to believe that compiler is perfect, either. So, I do my part, and leave the parts I can't be sure to the compiler. I'm not an hard-liner. I just want finer control on my code, and take full responsibility if it crashes and burns in a way it shouldn't, so plan and implement accordingly.