https://bugs.kde.org/show_bug.cgi?id=461070
--- Comment #14 from Maciej Stanczew <maciej.stancze...@gmail.com> --- Created attachment 160781 --> https://bugs.kde.org/attachment.cgi?id=160781&action=edit sensors: Correctly handle the return value of QCollator::compare I think I have found the root cause for this issue: it's in libksysguard, and was introduced with the fix to bug #440310. First, I located the place in the code which is impacted by changing between en_US and C locales: it's the Compare structure in SensorTreeModel.cpp, and its use as a comparator in an std::map in SensorTreeItem: > std::map<QString, std::unique_ptr<SensorTreeItem>, Compare> children; After adding some debug logs I noticed a weird behavior. Calls to Compare() seemed ok with en_US, but with the C locale I was getting a 'false' result regardless of the order of arguments: > # with LC_COLLATE=en_US.UTF-8 > Compare("cpu", "lmsensors") = true > Compare("lmsensors", "cpu") = false > # with LC_COLLATE=C.UTF-8 > Compare("cpu", "lmsensors") = false > Compare("lmsensors", "cpu") = false Adding more information to the logs revealed the cause of this behavior: > # with LC_COLLATE=en_US.UTF-8 > Compare("cpu", "lmsensors") = true, collator->compare() = -1 > Compare("lmsensors", "cpu") = false, collator->compare() = 1 > # with LC_COLLATE=C.UTF-8 > Compare("cpu", "lmsensors") = false, collator->compare() = -9 > Compare("lmsensors", "cpu") = false, collator->compare() = 9 We can see that with the C locale, 'collator->compare()' returns the lexicographical difference between characters (e.g. 'c' - 'l' = -9), and with en_US it squashes the value to -1. And since the code in Compare only checks against -1, all the other negative values are not handled correctly: > return collator->compare(first, second) == -1; Documentation about QCollator::compare() doesn't restrict the return value to [-1, 0, 1]: > Returns an integer less than, equal to, or greater than zero depending on > whether s1 sorts before, with or after s2. Thus comparing the returned value against -1 is based on an incorrect assumption, which just happens to work with most locales, but breaks with the C locale. If I'm not missing anything, the fix should be easy enough: change "== -1" to "< 0". I have prepared a patch based on 5.27.7 and tested it on my setup, and I get correct sensor list even with 'LC_COLLATE=C.UTF-8'. -- You are receiving this mail because: You are watching all bug changes.
