[ggreg84]

If you can re-compile all your source code, then ABI stability is not that important.

In the real world,

- people use operating systems to get work done,

- such work is often done with proprietary software that people buy, and that lot of people get paid to develop

- breaking such software is not acceptable, because it means that suddenly dozens of thousand of people can't work

- telling all those people to "stop working" until their software is fixed is not acceptable either.

People use Linux for work in the real world, and that's why Linux tries very hard not to break ABIs.

Microsoft has had a stable ABI for 30 years, and people still run software compiled 30 years ago on the latest Windows version today.

What this tells you about OpenBSD users, is another story.

[alerighi]

And even if you can recompile everything, it's still a pain to do so, and it's better to avoid doing so. Also recompiling the software may not be as simple, for example can require modifications of its source code to adapt it to newer versions of the compiler or other libraries that changed, and of course you can't build it on an older system since the ABI changed.

This is also the reason why containers are so popular these days, ship a software with all its dependencies to avoid having to recompile stuff each time you upgrade or change the operating system.

[ece]

The source-based Linux distros (Gentoo in my experience) do try to get better at keeping things working and moving forward when ABI breaks occur. Recompiling downstream dependencies (FFIs, libraries/packages), keeping the old library/packages around until a new ones are available, and keeping track of breaks/automating fixes with versioning all happen when for example a new boost or qt version comes out. All of this automated by the package manager. Proprietary packages that require fixed ABIs from certain libraries have *-compat packages in the gentoo repos, and other distros have this too.

Ultimately, it is about the APIs when you're compiling from source, a package that isn't using a new API is going to need the old library, and both might need to be compiled with and linked against the same toolchain. I think Linux and BSDs are closer than one might think here. Packaging and upstreams have both gotten better here over time I think, at least over the last couple of decades I've used Linux. I've only played around with the BSDs in VMs.

[moonbug]

no one uses Debian on s/390 for anything important anyway