53f88aa737
It's not a real leak in that the string data is being freed on program exit (or, more recently, QPixmapCache::clear()), but it can lead to lots of memory being bound for much longer than expected when users put in new QString keys without attempting to retrive them again. It can also lead to problems with QStringLiterals lingering around until after their underlying data has been freed. A bug in the Fusion style, generating new string keys for identical state, exposed this misbehavior, and one way to fix the resulting issue for the user is to make sure that QPixmapCache doesn't leak QString keys. The Fusion style issue with generating non-repeating keys for use with QPixmapCache should also be fixed, eventually, but this patch relegates that to an optimization issue (the caching is effectively non-existent), the resource exhaustion is gone now. The issue exists because the QString keys are internally mapped to QPixmapCache::Key's by way of a QHash<QString, Key> cacheKeys data structure. When the QCache, indexed by Key, not QString, decides to evict an entry, the Key is invalidated, but no-one was removing the corresponding entry from cacheKeys. So make the existing releaseKey(), used to invalidate copies of Keys referring to evicted pixmaps, do that, now. So as not to have to scan the whole cacheKeys QHash for the right Key, store the QString key, if any, inside the Key, so releaseKey() can retrieve it and use it for O(1) erasure from cacheKey. This allows removing the previous work-around in clear() (6ab0d25a09f5aeb7a5a062f7fd44e95ca761e21e), greatly simplify object(QString), and requires to rewrite all code that holds iterators or references into cacheKeys over an insertion into or removal from the QCache. Two (insert() and remove()) have already been done in prequel commits, so only flushDetachedPixmaps() was left. Fixes: QTBUG-112200 Change-Id: Ic93b0ed388ae963267fe242b491c6c941d146b99 Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org> Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io> (cherry picked from commit 56644240851443b1259bff2098d221068dd3e8b5) Reviewed-by: Marc Mutz <marc.mutz@qt.io>