On Thu, Apr 28, 2016 at 10:01 AM, Jos van den Oever <j...@vandenoever.info> wrote: > Hi all,
Hi Jos, > > A few days back dvratil reported errors in the KDE PIM unit tests. The tests > were writing > > QWARN : TestBlogger1::testNetwork() kf5.kservice.sycoca: ERROR: KSycoca > database corruption! > > On my laptop, I was seeing the same error when starting KF5 applications. I've > spent some time in the debugger today and I know what is going on in my > laptop. > > The KSycoca (KDE System Configuration Cache) database is a file with cached > information. It is created in KBuildSycoca::save. The file currently contains > four types of information: KMimeType, KServiceType, KService and > KServiceGroup. The top of the KSycoca file lists > - the format version > - the offsets for the four different parts > - XDG_DATA_DIRS for which it was created > - timestamp > - locale > - some hash > - paths to the cached directories with their mtimes > > The problems is this: the code for reading and writing of strings is not > symmetrical. Strings of any length can be written, but only strings of less > than 8192 bytes may be read. This limit is set in KSycocaUtilsPrivate::read. > The limit is probably there to avoid out-of-memory situations. > > On my laptop I have a lot of XDG data dirs. The length of the environment > variable is currently 4092 bytes. KSycocaBuild saves that as UTF-16 which > needs 8184 bytes. KBuildSycoca save that without complaint but complains when > reading it. > > Why would i need such a long XDG_DATA_DIRS? That is because on NixOS each > package has its own directory. This leads to this: > > XDG_DATA_DIRS= > /nix/store/0qm2gkssnfslm6nwhd3klwm54yhqx5rx-dbus-1.8.20/share > :/nix/store/r6j1sqknviayvqicy8zw049am0q6wywj-kcoreaddons-5.21.0/share > :/nix/store/qiq2vxxxsj0clv209xsv7w7yv2wrsbqb-breeze-icons-5.21.0/share > :/nix/store/l4ggdlcnj3sfky4zjlirf0hmqphzzc3y-kjobwidgets-5.21.0/share > ..... The CI system also has such a setup - so thanks for investigating this, it helps the CI system too :) > > In such a setup a working KSycoca really helps. > > The simplest solution here is to simply increase the magic number 8192 to e.g. > 65528. This is just a temporary buffer. > > Or we just check the size of the whole cache file (e.g. < 100M) and remove all > other limits. That would simplify > > KSycocaUtilsPrivate::read(*str, header.prefixes); > > to > > *str >> header.prefixes; > > Increasing the buffer size [1] fixes all but one of the failing unit test of > KService on NixOS. > > Cheers, > Jos Thanks, Ben > > [1] https://git.reviewboard.kde.org/r/127770/ > > _______________________________________________ > Kde-frameworks-devel mailing list > Kde-frameworks-devel@kde.org > https://mail.kde.org/mailman/listinfo/kde-frameworks-devel _______________________________________________ Kde-frameworks-devel mailing list Kde-frameworks-devel@kde.org https://mail.kde.org/mailman/listinfo/kde-frameworks-devel
