Comment by ablob | Hacker News Reader

Comment by ablob | Hacker News Reader

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If we're talking two's complement it's not undefined that is right. Having to emit checks though, that is where I beg to differ. A check is only useful if you want to actually change the behavior when it happens, otherwise it is useless. Furthermore, it might be "essentially free" from a branch prediction point, but low and behold caches exist. You would pollute both the instruction cache with those instructions _and_ the branch prediction cache. From this it doesn't follow at all, that there is no cost.

In the end small things do add up, and if you're adding many little things "because it doesn't cost much nowadays" you will end up with slow software and not have one specific bottleneck to look at. I do agree that having the option for checked operations is nice (see C#), but I have needed this behavior (branching on overflow) exactly once so far.

> A check is only useful if you want to actually change the behavior when it happens, otherwise it is useless.

You almost always want to change the behavior to erroring out on overflow. The few cases where overflow really is intended and fine can be handled by explicit opt-out.

And I refuse to buy the argument that "small things add up" in the world where we do string building and parsing every few microseconds. Checked math will have unnoticable impact compared to all the other things we do, in almost every type of program.

This string manipulation stuff is very common, and that's why in 2026, an age where science fiction has become a reality, many things are still absurdly slow. Exactly because of such sloppiness, which does accumulate in many cases, and when one least expected it.

100% agreed on the sloppiness. But overflow checking is not sloppiness. It's the opposite of sloppiness. Unchecked math is sloppiness, allowing overflows to happen silently and uncontrollably is sloppiness. It just so happens this kind of sloppiness makes code faster, unlike other kinds of sloppines that make code slower. Not doing necessary safety checks is faster than doing these necessary checks, but it doesn't make these checks any less necessary. Not validating user input also makes code faster, and is also sloppy.

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