File Stop-unloading-plugins-in-QPluginLoader-and-QFa... of Package libqt5-qtbase.16542

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File Stop-unloading-plugins-in-QPluginLoader-and-QFactoryLoader.patch of Package libqt5-qtbase.16542

From 8081ab4938b192bb740c5ee3004468aa6840563d Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Thu, 12 Nov 2015 10:14:51 -0800
Subject: [PATCH] Stop unloading plugins in QPluginLoader and QFactoryLoader

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
Task-number: QTBUG-52988
Discussed-on: http://lists.qt-project.org/pipermail/development/2015-November/023681.html
Change-Id: I6b3a1770e6c79cc4485a28ab286e069b88a149e5
---
 src/corelib/plugin/qfactoryloader.cpp | 6 ++++--
 src/corelib/plugin/qpluginloader.cpp  | 5 +++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/corelib/plugin/qfactoryloader.cpp b/src/corelib/plugin/qfactoryloader.cpp
index dcf1b1a..b6558f5 100644
--- a/src/corelib/plugin/qfactoryloader.cpp
+++ b/src/corelib/plugin/qfactoryloader.cpp
@@ -208,10 +208,12 @@ void QFactoryLoader::update()
                     ++keyUsageCount;
                 }
             }
-            if (keyUsageCount || keys.isEmpty())
+            if (keyUsageCount || keys.isEmpty()) {
+                library->setLoadHints(QLibrary::PreventUnloadHint); // once loaded, don't unload
                 d->libraryList += library;
-            else
+            } else {
                 library->release();
+            }
         }
     }
 #else
diff --git a/src/corelib/plugin/qpluginloader.cpp b/src/corelib/plugin/qpluginloader.cpp
index 37f2368..0ea8280 100644
--- a/src/corelib/plugin/qpluginloader.cpp
+++ b/src/corelib/plugin/qpluginloader.cpp
@@ -148,6 +148,7 @@ QPluginLoader::QPluginLoader(const QString &fileName, QObject *parent)
     : QObject(parent), d(0), did_load(false)
 {
     setFileName(fileName);
+    setLoadHints(QLibrary::PreventUnloadHint);
 }
 
 /*!
@@ -342,7 +343,7 @@ static QString locatePlugin(const QString& fileName)
 void QPluginLoader::setFileName(const QString &fileName)
 {
 #if defined(QT_SHARED)
-    QLibrary::LoadHints lh;
+    QLibrary::LoadHints lh = QLibrary::PreventUnloadHint;
     if (d) {
         lh = d->loadHints();
         d->release();
@@ -391,7 +392,7 @@ Q_GLOBAL_STATIC(StaticPluginList, staticPluginList)
     \brief Give the load() function some hints on how it should behave.
 
     You can give hints on how the symbols in the plugin are
-    resolved. By default, none of the hints are set.
+    resolved. By default since Qt 5.7, QLibrary::PreventUnloadHint is set.
 
     See the documentation of QLibrary::loadHints for a complete
     description of how this property works.
-- 
2.7.4

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File Stop-unloading-plugins-in-QPluginLoader-and-QFactoryLoader.patch of Package libqt5-qtbase.16542

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