Neil Bothwick schrieb am 05.07.2011 00:36: > On Tue, 05 Jul 2011 00:47:07 +0300, Nikos Chantziaras wrote: > >>> Why not? I see no downside to it but I'm willing to be educated. >>> >> >> Imagine this: A package is built by default with Gtk as well as >> with Qt support. There is no USE flag which would omit building >> with one of those. Then, the ebuild developer introduces those >> USE flags. --changed-use will not catch this, so you will continue >> having both Gtk and Qt support in the package, even though you're >> interested only in one of them (Gnome vs KDE user, for example). >> >> Or, imagine another scenario. A package offers multithreading >> support, resulting in a huge speed-up on machines with more than >> one core or CPU. But the ebuild configures and builds the package >> without multithreading, and there's no USE flag. When the ebuild >> dev puts a USE flag in there (and probably turns it on by >> default), --changed-use will also not catch this, because it's not >> a USE flag that changed, but instead a new one that wasn't there >> before. So you will continue running the package in its slow built, >> missing out on the big performance gain. > > changed-use also acts on added/removed flags, it just doesn't > recompile when the added/removed flag is not in use. So if my KDE > system has -gtk to use your first example, you are right in that > adding a gtk USE flag will not rebuild it until the next update and > my program will continue to work as it did. However, adding an > enabled multithreading USE flag as your second example will force a > rebuild. > > It seems that the trade off here is that I have may have cruft that > was previously compulsory but is now optional for a couple of weeks, > but I won't have to rebuild libreoffice or xulrunner every time a dev > tweaks a USE flag that doesn't affect me. > > That seems a reasonable trade to me, but I still have an open mind.
The first scenario from Nikos seems valid but the second one with the per default enabled USE flag will trigger a rebuild as --changed-use only avoid rebuilds for disabled USE flags which are added or removed. I personally can only think of another issue. There may be a completely new use flag which you might want to enable. With --changed-use the changes wont show up in the depgraph and you are not aware of the new feature. You will only get them later when there is a version/revision bump. These are all minor things and as you said it is a reasonable trade for you to avoid useless rebuilds. Using --newuse instead of --changed-use is just my personal preference. Many systems are idling around most of the time, with --newuse they have to do something :) -- Regards, Daniel
signature.asc
Description: OpenPGP digital signature
