Kudos to Markos who basically gave me the title for this blog post!
I’ve spent the past week or so away from computers, I’m having some personal trouble, tied with bad migraines that would have burnt the hell out of me. I came back to updating my systems today, and I received a nasty surprise. Unmasked libpng 1.4 is wrecking havoc on so many systems that it’s not even funny.
I’m not complaining about the fact that we’ve finally unmasked the new libpng, it was needed and we should probably proceed on getting it stable soonish as well. What I complain about is that we’re hitting the same obstacles we hit with libexpat:
- we still don’t have enabled
--as-neededby default, which would reduce considerably the amount of packages that actually need to be rebuilt after such an update (and, by the way, not using
--as-neededalso increases tremendously the chance that some program will be loading both 1.2 and 1.4 versions, with the usual trouble of symbols’ collisions);
- we still haven’t solved the problem with libtool archives , requiring the rebuild (or nasty hack) of a number of packages for no good reasons.
The worst part is that I have been preaching about both things for a while, a few years I’d say, and yet we have not gotten our heads out of the sand, so we hit users in the face after this kind of updates. Still.
--as-needed, only a fraction of the packages installed in the system will actually link against the libtool file, and only those would need to be rebuilt; without it, it’s very likely almost all the libtool-using packages, as well as most
pkg-config using packages will be linking in libpng as a dependency of other libraries, such as GTK+ or Qt. And since you will start updating from those libraries, the newly-started packages will have problems because both libpng versions will be loaded at the same time: once from the library and once from the application.
For what concerns the
.la files, the problem is mostly at buildtime and it makes it very very difficult to get out of the mess caused by the update, as a number of packages will start lamenting of missing targets for
-lpng12. The solution for this would be to, obviously, carefully remove
.la files within the ebuilds; this way we reduce the chances that the dependencies end up polluting packages that would, otherwise, have no involvement whatsoever with libpng.
Unfortunately, removing all the libpng file indiscriminately is a Bad Idea™ (and yes, I know some people experimented with that, I still maintain it’s a bad idea!). What you want to do is to reduce their impact as much as possible, but to do so you have to do some extra work, and that requires developers to understand the problem and accept working on a solution, even a temporary, imperfect one, to avoid staying in the problem area.
Do you remember when I checked eog (Eyes of Gnome)
.la files resulting in stating clearly that they are totally useless? Well, eog still installs them; sure enough they are not excessively important in this situation, as they are not linked against, but they will create false positives in
revdep-rebuild for instance. Even my flowchart has gone mostly unused by developers.
And we still don’t have any way to sanitise those files within Portage;
lafilefixer does solve some stuff, but it’s not part of Portage proper, nor it’s integrated with it. If you want, in the future, to reduce your system’s pollution, do something like this:
This way the files will be sanitised before being merged in the system, and you won’t have to fix them manually.
Will we ever learn?