> they don't normally track the build backend as a dependency... It's the "rebuild from source every time" aspect of Gentoo that forces that connection

I don't follow. This feels like Gentoo is mishandling build-tool dependencies.

Does Gentoo also recompile every C/C++ library in the dependency tree every time GCC pushes a minor version bump?

> This feels like Gentoo is mishandling build-tool dependencies.

I would say it's doing what it believes is necessary for the Python ecosystem. The build backend is an explicit part of the specification of a Python project.

> Does Gentoo also recompile every C/C++ library in the dependency tree every time GCC pushes a minor version bump?

No, because C/C++ libraries don't have an explicit specification of the build tool to be used in their project, the way a Python project does.

> I don't follow.

I don't either. I used to run Gentoo for quite a few years in the past and build dependency updates would not trigger rebuilds of build-dependent packages.

Rebuilding the entire system with a new GCC was recommended by the documentation, but there was nothing in Portage forcing it. Neither would you rebuild the system if, e.g. make got an update.

No, and not with clang or llvm or rust. When we get a new Golang tho, that does rebuild stuff built with Go. And big perl updates cause a rebuild for perl packages.

IIRC, rebuilds to GCC outputs are/were only recommended when the compiler "profile" changes. So basically whenever the ABI could no longer be guaranteed.

Strictly speaking, they should, right? Differences in GCC could produce differences in anything it compiles.