From 2f226336a2aeb477b7ba339b6c3a63abb69746c3 Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Sat, 25 Mar 2023 13:32:26 -0400
Subject: [PATCH] QPluginLoader: don't instantiante multiple, identical
 instances

This can happen if the same project has two or more Q_IMPORT_PLUGIN
macros in their source. And that can happen when converting from qmake-
based builds to CMake, as qmake didn't generate a source file with the
macro but CMake does.

[ChangeLog][QtCore][QPluginLoader] staticInstances() will not call
duplicated registrations of the same instantiation function, which can
only happen as a result of duplicated Q_IMPORT_PLUGIN for the same
plugin name.

Fixes: QTBUG-102745
Pick-to: 6.2 6.5
Change-Id: Idd5e1bb52be047d7b4fffffd174fb9dd62d8583d
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
---
 src/corelib/plugin/qpluginloader.cpp          | 14 +++++++++-
 .../qpluginloader/tst_qpluginloader.cpp       | 26 ++++++++++++++-----
 2 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/src/corelib/plugin/qpluginloader.cpp b/src/corelib/plugin/qpluginloader.cpp
index e07f1c2774..b8052d5596 100644
--- a/src/corelib/plugin/qpluginloader.cpp
+++ b/src/corelib/plugin/qpluginloader.cpp
@@ -379,7 +379,19 @@ Q_GLOBAL_STATIC(StaticPluginList, staticPluginList)
 */
 void Q_CORE_EXPORT qRegisterStaticPluginFunction(QStaticPlugin plugin)
 {
-    staticPluginList()->append(plugin);
+    // using operator* because we shouldn't be registering plugins while
+    // unloading the application!
+    StaticPluginList &plugins = *staticPluginList;
+
+    // insert the plugin in the list, sorted by address, so we can detect
+    // duplicate registrations
+    auto comparator = [=](const QStaticPlugin &p1, const QStaticPlugin &p2) {
+        using Less = std::less<decltype(plugin.instance)>;
+        return Less{}(p1.instance, p2.instance);
+    };
+    auto pos = std::lower_bound(plugins.constBegin(), plugins.constEnd(), plugin, comparator);
+    if (pos == plugins.constEnd() || pos->instance != plugin.instance)
+        plugins.insert(pos, plugin);
 }
 
 /*!
diff --git a/tests/auto/corelib/plugin/qpluginloader/tst_qpluginloader.cpp b/tests/auto/corelib/plugin/qpluginloader/tst_qpluginloader.cpp
index adea6af515..e6d1785dca 100644
--- a/tests/auto/corelib/plugin/qpluginloader/tst_qpluginloader.cpp
+++ b/tests/auto/corelib/plugin/qpluginloader/tst_qpluginloader.cpp
@@ -206,6 +206,7 @@ private slots:
     void preloadedPlugin_data();
     void preloadedPlugin();
     void staticPlugins();
+    void reregisteredStaticPlugins();
 };
 
 Q_IMPORT_PLUGIN(StaticPlugin)
@@ -1080,19 +1081,18 @@ void tst_QPluginLoader::staticPlugins()
     const QObjectList instances = QPluginLoader::staticInstances();
     QVERIFY(instances.size());
 
-    bool found = false;
-    for (QObject *obj : instances) {
-        found = obj->metaObject()->className() == QLatin1String("StaticPlugin");
-        if (found)
-            break;
-    }
-    QVERIFY(found);
+    // ensure the our plugin only shows up once
+    int foundCount = std::count_if(instances.begin(), instances.end(), [](QObject *obj) {
+            return obj->metaObject()->className() == QLatin1String("StaticPlugin");
+    });
+    QCOMPARE(foundCount, 1);
 
     const auto plugins = QPluginLoader::staticPlugins();
     QCOMPARE(plugins.size(), instances.size());
 
     // find the metadata
     QJsonObject metaData;
+    bool found = false;
     for (const auto &p : plugins) {
         metaData = p.metaData();
         found = metaData.value("className").toString() == QLatin1String("StaticPlugin");
@@ -1108,6 +1108,18 @@ void tst_QPluginLoader::staticPlugins()
     QCOMPARE(metaData.value("URI").toString(), "qt.test.pluginloader.staticplugin");
 }
 
+void tst_QPluginLoader::reregisteredStaticPlugins()
+{
+    // the Q_IMPORT_PLUGIN macro will have already done this
+    qRegisterStaticPluginFunction(qt_static_plugin_StaticPlugin());
+    staticPlugins();
+    if (QTest::currentTestFailed())
+        return;
+
+    qRegisterStaticPluginFunction(qt_static_plugin_StaticPlugin());
+    staticPlugins();
+}
+
 
 QTEST_MAIN(tst_QPluginLoader)
 #include "tst_qpluginloader.moc"