Glibc has a terrible history of binary incompatibility. If that's so hard to believe, try running binaries built on one distribution on other distributions. Linux has two stable ABIs: the kernel ABI for static programs, and, ironically, WINE.
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.
Not sure how the comments about alpine or bionic relate either to my claim that cross distro glibc is fine.
Overall, both of our points of view on compatibility were discussed well in that thread; we probably shouldn't repeat ourselves. :)
> 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.
By that definition, any change of any kind will break ABI, Hyrum’s law and spacebar heating and all that.
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.
- Linus Torvalds
That bug report was a good read.
https://docs.appimage.org/reference/best-practices.html
I hear you about WINE though.
You can also compile using old distro and old Glibc to get similar effect. Though you would miss the advances of the newer compilers.