Destructor for the "root components" of plugins are only called if we explicit unload(), but documentation of QPluginLoader and QPluginLoader::instance() suggests that they would be automatically deleted:

"Once loaded, plugins remain in memory until all instances of QPluginLoader has been unloaded, or until the application terminates."

"When the library is finally unloaded, the root component will automatically be deleted."

Also, destructor of "root component" of static plugins are never called as well.

The attached file has a small example, where I've expected both destructor to be called, but no one is.