5 ms·

It's not because of that. There exist countless BSD compatible code out there, and many are taken and used in projects like this. CRC codes being an obvious exa

• tialaramex 3y ago
  > the facilities to support your general language / runtime environment is not up yet. Rust's [T].sort_unstable() is part of core, that is, the code to sort a slice of arbitrary type T doesn't need the allocator, operating system etc. Only if you want a fast stable sort do you need to wait for such an environment because their fast stable sort needs an allocator, I doubt that FreeBSD needs a stable sort here.
  • throwawaylinux 3y ago
    I'm not sure what part of my post you are addressing. If you had a kernel written in Rust, you would have to bring up the rust runtime environment as part of the boot process. You don't just magically get it because that's the language you used, whether it is "core" or not. You can't even execute simple functions before you have set up stack, and in this case apparently there is a constraint on stack usage. And evidently they do need a stable sort. In any case my main point is that it's not anything to do with dependency management, not quibbling about whether or not some language could support this function at this exact point of the boot.
    • tialaramex 3y ago
      > you would have to bring up the rust runtime environment as part of the boot process Like the existing C runtime environment, this just isn't a big deal by the time we've got here. If you're the code for initialising the DRAM controller then sure, that's pretty intimidating. But this is all happening much later, we're part of an operating system, we were already loaded from disk. > And evidently they do need a stable sort. How so? They appear to even have a deliberate tie-breaking mechanism in their data structure, which suggests if order actually matters you're expected to specify when creating the data, not rely on stability to do what you expected.
      • throwawaylinux 3y ago
        > > you would have to bring up the rust runtime environment as part of the boot process > Like the existing C runtime environment, this just isn't a big deal by the time we've got here. If you're the code for initialising the DRAM controller then sure, that's pretty intimidating. But this is all happening much later, we're part of an operating system, we were already loaded from disk. I don't know what you're trying to say. The code which is written here that we are discussing is in a constrained environment where the regular kernel runtime facilities are not all available. This was cited as one of the reasons cited for open coding a very simple algorithm. > > And evidently they do need a stable sort. > How so? From reading comments from patch author here.
  • fanf2 3y ago
    It does need to be stable, which is why the replacement is mergesort. The SYSINITs need to bring up the system in a particular order. I dunno why there are both explicit ordering (the sort keys) and implicit ordering (the stability requirement), perhaps cperciva can chime in. Based on when I last looked at this code, I guess the explicit ordering is to do with startup phases, and the implicit ordering is because of the way SYSINITs are (or were?) implemented using linker sets, which have more guarantees about ordering than __attribute__((constructor)) and other similar functionality.
    • tialaramex 3y ago
      > I dunno why there are both explicit ordering (the sort keys) and implicit ordering (the stability requirement), perhaps cperciva can chime in. In the event Colin is looking at this sub-thread now I'm intrigued too.
      • cperciva 3y ago
        There isn't supposed to be an implicit ordering requirement. But a number of bugs have happened in the past because people didn't order properly. What we need isn't actually "stable" so much as "consistent from one boot to the next" to make sure that ordering bugs don't end up being heisenbugs.
        • tialaramex 3y ago
          > a number of bugs have happened in the past because people didn't order properly. This may be impractical, but I think my reaction would be to re-design it so that the ordering was mechanically a full order, even if culturally the people writing these things don't need to specify if they don't want to. e.g. maybe a macro can turn your existing explicit order into high bits of a value, and then a "noise" factor into low bits, where that "noise" is derived from a date integer like 20230822 or filenames or whatever, and truly order on the entire value. The idea is, this means any hidden order is the same for everyone, Intel laptop test rig, ARM WiFi cameras at customer site, last week's build, this week's build, Colin's build, the CI system's build, they're all using the same order, because while heisenbugs are strictly worse, "It only happens with my setup" is also extremely frustrating. When people discover a hidden ordering requirement they can adjust the "real" ordering accordingly, just now there's a deliberate systemic consistency. Probably not worth all the bother, but I think I couldn't live with the "stable sort to avoid heisenbugs" situation.
• IshKebab 3y ago
  > the facilities to support your general language / runtime environment is not up yet. What facilities does Rust's sort require? It probably just needs a bit of stack but that's it. That qsort implementation doesn't look like it needs anything either tbh, though I only skimmed it.
  • throwawaylinux 3y ago
    Not sure, the qsort is recursive and stack limitations were mentioned. But the point being that the reason they don't use their library functions because it's a constrained environment. Maybe they could permit some of their sort library functions to be used in such a constrained environment, sure. Don't need rust to do that, just need to be happy that the implementation is suitable for purpose. Which they would have to do regardless of what language and runtime they were using.