8 ms·

https://bugzilla.redhat.com/show_bug.cgi?id=638477 https://bugzilla.redhat.com/show_bug.cgi?id=638477 is the most "famous" example. There are also much less we

by pg83 29d ago

https://bugzilla.redhat.com/show_bug.cgi?id=638477 https://bugzilla.redhat.com/show_bug.cgi?id=638477 is the most "famous" example. There are also much less well-known "little things" that regularly pop up here and there. > If your CI uses an older glibc you should be fine AFAIK. In any case, my binaries work not only under glibc, but also under Alpine, and (work in progress) under android/bionic.

vlovich123 29d ago
Not sure what you’re trying to show with that bug report but it’s not a case of cross distro glibc issues. If I read correctly it’s a vanilla behavioral change that exposed preexisting UB in flash. Not sure how the comments about alpine or bionic relate either to my claim that cross distro glibc is fine.
- pg83 29d ago
  It depends on how we define the ABI. I see it as a set of client-visible invariants that they rely on. In my world, glibc changed the client's visible invariants, breaking the client. The client works on one glibc-based host, but not on another. What is this if not "a case of cross-distro glibc issues?" Overall, both of our points of view on compatibility were discussed well in that thread; we probably shouldn't repeat ourselves. :)
  - account42 29d ago
    ABI is not "whatever happens to work with this distro" but "what programs that comply with the API contract compile to". Overlapping memcpy arguments is an API contract violation and thus not something covered by the ABI either. This distinction is the entire reason why C has a separate memmove function. You can't just make up your own imaginary ABI contract and then blame the system when it doesn't fulfill it. That's going to result in self-inflicted plain on any OS.
    - pg83 29d ago
      It's so good that Linus thinks differently!
      - ninkendo 29d ago
        Even Linus’s comments in that bug hedge things a bit: > and that if people depend on interfaces we exported having side effects that weren't intentional, we try to fix things so that they still work unless there is a major reason not to. (Emphasis mine.) In the Flash case, they changed the direction memcpy works in, in a way that didn’t actually improve any performance (Linus did benchmarks to show it) and Linus’s point was that there’s no upside to the change, and only downsides, so on the whole it makes no sense to keep the changed memcpy. You could imagine plenty of scenarios where existing behavior truly is broken, and show that no popular software depends on the brokenness (which is why distros are in a great place to do these kinds of smoke tests, they have thousands of packages they can test), and make a judgement call. A “zero regressions no matter what” policy is impossible in practice due to Hyrum’s law, at some point you have to use common sense and draw the line somewhere sensible.
  - ninkendo 29d ago
    > It depends on how we define the ABI. I see it as a set of client-visible invariants that they rely on By that definition, any change of any kind will break ABI, Hyrum’s law and spacebar heating and all that.
  - vlovich123 28d ago
    Did the distro apply a patch to glibc that broke things that others did not? Or did they pick up a newer version of glibc that other distros hadn’t? Yes, different distributions run on different versions of glibc. And different versions of glibc may have subtle differences in runtime behavior. That’s still ultimately a glibc back compost issue, not some kind of bug specific to glibc.
__turbobrew__ 29d ago
> Quite frankly, I find your attitude to be annoying and downright stupid. - Linus Torvalds That bug report was a good read.

by pg83 29d ago

vlovich123 29d ago

Not sure what you’re trying to show with that bug report but it’s not a case of cross distro glibc issues. If I read correctly it’s a vanilla behavioral change that exposed preexisting UB in flash. Not sure how the comments about alpine or bionic relate either to my claim that cross distro glibc is fine.

pg83 29d ago
It depends on how we define the ABI. I see it as a set of client-visible invariants that they rely on. In my world, glibc changed the client's visible invariants, breaking the client. The client works on one glibc-based host, but not on another. What is this if not "a case of cross-distro glibc issues?" Overall, both of our points of view on compatibility were discussed well in that thread; we probably shouldn't repeat ourselves. :)
- account42 29d ago
  ABI is not "whatever happens to work with this distro" but "what programs that comply with the API contract compile to". Overlapping memcpy arguments is an API contract violation and thus not something covered by the ABI either. This distinction is the entire reason why C has a separate memmove function. You can't just make up your own imaginary ABI contract and then blame the system when it doesn't fulfill it. That's going to result in self-inflicted plain on any OS.
  - pg83 29d ago
    It's so good that Linus thinks differently!
    - ninkendo 29d ago
      Even Linus’s comments in that bug hedge things a bit: > and that if people depend on interfaces we exported having side effects that weren't intentional, we try to fix things so that they still work unless there is a major reason not to. (Emphasis mine.) In the Flash case, they changed the direction memcpy works in, in a way that didn’t actually improve any performance (Linus did benchmarks to show it) and Linus’s point was that there’s no upside to the change, and only downsides, so on the whole it makes no sense to keep the changed memcpy. You could imagine plenty of scenarios where existing behavior truly is broken, and show that no popular software depends on the brokenness (which is why distros are in a great place to do these kinds of smoke tests, they have thousands of packages they can test), and make a judgement call. A “zero regressions no matter what” policy is impossible in practice due to Hyrum’s law, at some point you have to use common sense and draw the line somewhere sensible.
- ninkendo 29d ago
  > It depends on how we define the ABI. I see it as a set of client-visible invariants that they rely on By that definition, any change of any kind will break ABI, Hyrum’s law and spacebar heating and all that.
- vlovich123 28d ago
  Did the distro apply a patch to glibc that broke things that others did not? Or did they pick up a newer version of glibc that other distros hadn’t? Yes, different distributions run on different versions of glibc. And different versions of glibc may have subtle differences in runtime behavior. That’s still ultimately a glibc back compost issue, not some kind of bug specific to glibc.

__turbobrew__ 29d ago

> Quite frankly, I find your attitude to be annoying and downright stupid. - Linus Torvalds That bug report was a good read.