this post was submitted on 17 Oct 2024
1370 points (99.0% liked)
RetroGaming
19568 readers
539 users here now
Vintage gaming community.
Rules:
- Be kind.
- No spam or soliciting for money.
- No racism or other bigotry allowed.
- Obviously nothing illegal.
If you see these please report them.
founded 1 year ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
A compiler making assumptions like that about undefined behaviour sounds just like a bug. Maybe the bug is in the spec rather than the compiler, but I can't think of any time it would be better to optimize that code out entirely because UB is detected rather than just throwing an error or warning and otherwise ignoring the edge cases where the behaviour might break. It sounds like the worst possible option exactly for the reasons listed in that blog.
The thing about UB is that many optimizations are possible precisely because the spec specified it as UB. And the spec did so in order to make these optimizations possible.
Codebases are not 6 lines long, they are hundreds of thousands. Without optimizations like those, many CPU cycles would be lost to unnecessary code being executed.
If you write C/C++, it is because you either hate yourself or the application's performance is important, and these optimizations are needed.
The reason rust is so impressive nowadays is that you can write high performing code without risking accidentally doing UB. And if you are going to write code that might result in UB, you have to explicitly state so with
unsafe. But for C/C++, there's no saving. If you want your compiler to optimize code in those languages, you are going to have loaded guns pointing at your feet all the time.