alt Hacker News> 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.
> The build backend is an explicit part of the specification of a Python project
Nothing in the Python spec forces Gentoo to invalidate the downstream package every time build-system dependencies update - that's a behaviour they've decided is correct on their own.
> C/C++ libraries don't have an explicit specification of the build tool to be used in their project
They don't have a standard way to specify such, but they have an implicit dependency on the installed compiler toolchain, and it would be just as valid to interpret "no way to specify a build-system dependency" as "always rebuild" when the build tool updates