QPluginLoader hasn't unloaded in its destructor since Qt 5.0, but we
missed the equivalent code in QFactoryLoader (which bypasses
QPluginLoader). Besides, QPluginLoader::unload() was still doing
unloading, which it won't anymore.
Not unloading plugins is Qt's policy, as decided during the 5.0
development process and reaffirmed now in 5.6. This is due to static
data in plugins leaking out and remaining in use past the unloading of
the plugin, causing crashes.
This does not affect QLibrary and QLibrary::unload(). Those are meant
for non-Qt loadable modules, so unloading them may be safe.
Task-number: QTBUG-49061
Discussed-on: http://lists.qt-project.org/pipermail/development/2015-November/023681.html
Change-Id: I461e9fc7199748faa187ffff1416070f138df8db
(cherry picked from commit 494376f980)
Discussed-again-on: http://lists.qt-project.org/pipermail/development/2016-October/027476.html
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
ca4d93d85e