Review Request 127866: Oxygen: Fix QCache usage

Michael Pyne mpyne at
Sun May 8 06:03:45 BST 2016

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Review request for kde-workspace and Hugo Pereira Da Costa.

Repository: oxygen


This should mostly complete the QCache fixes I kicked off in a previous RR, 127837. Hugo noted there were many other similar usages, and boy he wasn't kidding! ;) The long story short is that these usages can theoretically cause use-after-free behavior (which can lead to crashes and even undefined behavior if the compiler ever gets smart).

*NOTE* It is -much- easier to review if you download the diff to your git repository for oxygen and then run "git diff -b" to ignore whitespace changes, particularly for the QPixmap changes.

For QPixmaps we return values instead of pointers, so we simply make a separate copy to be cached when we do insert. For QColor we return references to values so we *must* return pointers, and those have to be owned by a QCache to avoid memleaks. So I added a helper function to loop until the cache accepts the new entry. TileSets are a similar concern, except those have manual loops since I was uncertain about whether TileSet's copy constructor was the best idea or not.

This fixes a ton of Coverity issues (59717 - 259733, 259739, 259742 - 259752, 1336154, 1336155) and might be associated with Qt bug 38142 and KDE bug 219055 (which doesn't actually appear to be a dupe of a different bug to me...).


  kstyle/oxygenstylehelper.cpp 612ba37 
  liboxygen/oxygenhelper.h a6453a0 
  liboxygen/oxygenhelper.cpp 4843604 
  liboxygen/oxygenshadowcache.cpp 907e586 



Compiled without warnings, installed and ran `oxygen-demo5 -style oxygen`. Used the GUI Benchmark feature to automatically cycle through all the listed features -- no crashes or obvious rendering errors.


Michael Pyne

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