> On Oct. 29, 2012, 11:18 a.m., David Faure wrote: > > This assumes that QRegExp::exactMatch is re-entrant, i.e. that it doesn't > > update an internal cache on demand. I'm not so sure of that, the regexp > > parsing sounds like a very good candidate for on-demand parsing, unless you > > make extra sure that it's all done upfront. > > Simeon Bird wrote: > The Qt documentation claims it is: > > http://qt-project.org/doc/qt-4.8/qregexp.html > "Note: All functions in this class are reentrant." > > (although it's true that I hadn't checked up to now, so that was still a > good question)
Never trust documentation :-) I had a look at the source code, and found indeed 1) on-demand initializations 2) no locking mechanism. So I wrote a test program, and guess what? It gives different output from one run to the next. It's memcheck-clean, but helgrind manages to spot the issue in some runs. http://www.davidfaure.fr/2012/qregexp_race.cpp http://www.davidfaure.fr/2012/qregexp-helgrind-log The program is supposed to write out "true true true" but only does so 1 time out of 8 on average, in my tests. Nice, heh? => The documentation is wrong. I'll submit a docu fix to Qt... - David ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: http://git.reviewboard.kde.org/r/107082/#review21082 ----------------------------------------------------------- On Oct. 27, 2012, 6:29 p.m., Simeon Bird wrote: > > ----------------------------------------------------------- > This is an automatically generated e-mail. To reply, visit: > http://git.reviewboard.kde.org/r/107082/ > ----------------------------------------------------------- > > (Updated Oct. 27, 2012, 6:29 p.m.) > > > Review request for Nepomuk, Vishesh Handa and Sebastian Trueg. > > > Description > ------- > > Some fairly trivial misc improvements to the filewatch service. Probably > don't make a big difference, but probably a good idea. > > - Use QReadWriteLock instead of QMutex in FileIndexerConfig, thus allowing > multiple threads to call shouldFolderBeIndexed at once (not that we really do > that right now). > > - Add the IN_EXCL_UNLINK inotify flag. On recent (2.6.36) kernels, this means > we don't generate events for files once > they have been unlinked from the directory we are watching. Prevents waking > up for some already-deleted temporary files. > > > Diffs > ----- > > services/fileindexer/fileindexerconfig.h 7debaf3 > services/fileindexer/fileindexerconfig.cpp 5226a79 > services/filewatch/kinotify.h 6e3f1c0 > services/filewatch/kinotify.cpp 9868b90 > > Diff: http://git.reviewboard.kde.org/r/107082/diff/ > > > Testing > ------- > > Compiled, ran for a bit, didn't seem to break anything. > > > Thanks, > > Simeon Bird > >
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