@preserved-rebuild: Why are rebuilds not automatic? [SOLVED]

[ermor]

Hello everyone!

After my daily update, Portage complained about an old version of a library that was kept because xfce-base/libxfce4windowing was built against it, if I remember correctly. Unfortunately I can't quite find the exact message in my logs.

Portage told me I could use the "emerge @preserved-rebuild" command to rebuild the package against the new version of the library, and a few articles I found seemed to suggest I should indeed do it (or at the very least, that there was no particular reason not to do it), but I'm a bit puzzled.

If I understand these articles correctly, the reason why the package wasn't automatically rebuilt was that it was still referring to an old version of the library, which did not trigger a rebuild of the package after it was detected that the library was updated. But in that case, would it not be better to leave it like that? Presumably, if the maintainer referred to that version specifically, he might have had a good reason. Or was I just too fast in upgrading after the library updated, and these things have to be manually set by the package maintainers? It's the first time this happens to me, so I'm a bit surprised, I just assumed all packages were immediately set to be rebuilt upon their dependencies being updated. Should I have waited for the issue to resolve "naturally" after a few days?

[grknight]

First, try to run emerge --ask --depclean to clean up libraries that are no longer needed.
If the message still remains, then you could certainly run the @preserved-rebuild.
This is technically a bug if the depclean does not clean up such items as portage can do automatic rebuilds with a certain ebuild change.

[ermor]

[CaptainBlood]

From time to time, gentoo world update triggers some package rebuilds.
Once a gentoo world update has been proceeded, it could be emerge does indeed ask for