QPlugin: add qt_plugin_query_metadata_v2() to dynamic plugins

They return a pointer to the actual header, skipping the magic string.
This is done in preparation for the header located in an ELF note, which
won't have the magic.

Change-Id: I3eb1bd30e0124f89a052fffd16a8229bec2ad588
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

4 files changed, 32 insertions, 25 deletions

diff --git a/src/corelib/plugin/qlibrary.cpp b/src/corelib/plugin/qlibrary.cpp
index a8c6644bfd..e18a5080f5 100644
--- a/src/corelib/plugin/qlibrary.cpp
+++ b/src/corelib/plugin/qlibrary.cpp
@@ -682,18 +682,31 @@ static bool qt_get_metadata(QLibraryPrivate *priv, QString *errMsg)
         return false;
     };
 
-    QFunctionPointer pfn = priv->resolve("qt_plugin_query_metadata");
-    if (!pfn)
-        return error(QLibrary::tr("entrypoint 'qt_plugin_query_metadata' not found"));
+    QPluginMetaData metaData;
+    QFunctionPointer pfn = priv->resolve("qt_plugin_query_metadata_v2");
+    if (pfn) {
+        metaData = reinterpret_cast<QPluginMetaData (*)()>(pfn)();
+#if QT_VERSION <= QT_VERSION_CHECK(7, 0, 0)
+    } else if ((pfn = priv->resolve("qt_plugin_query_metadata"))) {
+        metaData = reinterpret_cast<QPluginMetaData (*)()>(pfn)();
+        if (metaData.size < sizeof(QPluginMetaData::MagicHeader))
+            return error(QLibrary::tr("metadata too small"));
+
+        // adjust the meta data to point to the header
+        auto data = reinterpret_cast<const char *>(metaData.data);
+        data += sizeof(QPluginMetaData::MagicString);
+        metaData.data = data;
+        metaData.size -= sizeof(QPluginMetaData::MagicString);
+#endif
+    } else {
+        return error(QLibrary::tr("entrypoint to query the plugin meta data not found"));
+    }
 
-    auto metaData = reinterpret_cast<QPluginMetaData (*)()>(pfn)();
-    auto data = reinterpret_cast<const char *>(metaData.data);
-    if (metaData.size < sizeof(QPluginMetaData::MagicHeader))
+    if (metaData.size < sizeof(QPluginMetaData::Header))
         return error(QLibrary::tr("metadata too small"));
 
-    data += sizeof(QPluginMetaData::MagicString);
-    metaData.size -= sizeof(QPluginMetaData::MagicString);
-    QJsonDocument doc = qJsonFromRawLibraryMetaData(data, metaData.size, errMsg);
+    QJsonDocument doc = qJsonFromRawLibraryMetaData(reinterpret_cast<const char *>(metaData.data),
+                                                    metaData.size, errMsg);
     if (doc.isNull())
         return false;           // error message already set
 
diff --git a/src/corelib/plugin/qplugin.h b/src/corelib/plugin/qplugin.h
index 884f510541..d70324b560 100644
--- a/src/corelib/plugin/qplugin.h
+++ b/src/corelib/plugin/qplugin.h
@@ -155,13 +155,14 @@ void Q_CORE_EXPORT qRegisterStaticPluginFunction(QStaticPlugin staticPlugin);
 // Since Qt 6.3
 template <auto (&PluginMetaData)> class QPluginMetaDataV2
 {
-    struct RegularPayload {
-        QPluginMetaData::MagicHeader header = {};
+    struct RegularPayload : QPluginMetaData::MagicHeader {
+        static constexpr size_t HeaderOffset = offsetof(QPluginMetaData::MagicHeader, header);
         quint8 payload[sizeof(PluginMetaData)] = {};
         constexpr RegularPayload() { QPluginMetaData::copy(payload, PluginMetaData); }
     };
 
     struct StaticPayload {
+        static constexpr size_t HeaderOffset = 0;
         QPluginMetaData::Header header = {};
         quint8 payload[sizeof(PluginMetaData)] = {};
         constexpr StaticPayload() { QPluginMetaData::copy(payload, PluginMetaData); }
@@ -180,7 +181,9 @@ template <auto (&PluginMetaData)> class QPluginMetaDataV2
 public:
     operator QPluginMetaData() const
     {
-        return { &payload, sizeof(payload) };
+        Q_ASSERT(reinterpret_cast<const char *>(&payload) + Payload::HeaderOffset ==
+                 reinterpret_cast<const char *>(&payload.header));
+        return { &payload.header, sizeof(payload) - Payload::HeaderOffset };
     }
 };
 
@@ -242,7 +245,7 @@ public:
             QT_MOC_EXPORT_PLUGIN_COMMON(PLUGINCLASS, PLUGINCLASSNAME)
 
 #  define QT_MOC_EXPORT_PLUGIN_V2(PLUGINCLASS, MANGLEDNAME, MD)                                 \
-    extern "C" Q_DECL_EXPORT QT_PREPEND_NAMESPACE(QPluginMetaData) qt_plugin_query_metadata()   \
+    extern "C" Q_DECL_EXPORT QT_PREPEND_NAMESPACE(QPluginMetaData) qt_plugin_query_metadata_v2()\
     { static constexpr QT_PLUGIN_METADATAV2_SECTION QPluginMetaDataV2<MD> md{}; return md; }    \
     QT_MOC_EXPORT_PLUGIN_COMMON(PLUGINCLASS, MANGLEDNAME)
 #endif
diff --git a/tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp b/tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp
index e55fbf2137..ec7f7dc0dc 100644
--- a/tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp
+++ b/tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp
@@ -1021,7 +1021,7 @@ void tst_QGuiApplication::genericPluginsAndWindowSystemEvents()
     QCoreApplication::postEvent(&testReceiver, new QEvent(QEvent::User));
     QCOMPARE(testReceiver.customEvents, 0);
 
-    QStaticPlugin testPluginInfo(qt_plugin_instance, qt_plugin_query_metadata);
+    QStaticPlugin testPluginInfo(qt_plugin_instance, qt_plugin_query_metadata_v2);
     qRegisterStaticPluginFunction(testPluginInfo);
     int argc = 3;
     char *argv[] = { const_cast<char*>(QTest::currentAppName()), const_cast<char*>("-plugin"), const_cast<char*>("testplugin") };
diff --git a/tests/auto/tools/moc/tst_moc.cpp b/tests/auto/tools/moc/tst_moc.cpp
index 6776b6e509..cd69ea893c 100644
--- a/tests/auto/tools/moc/tst_moc.cpp
+++ b/tests/auto/tools/moc/tst_moc.cpp
@@ -1468,20 +1468,11 @@ void tst_Moc::environmentIncludePaths()
 // plugin_metadata.h contains a plugin which we register here. Since we're not building this
 // application as a plugin, we need top copy some of the initializer code found in qplugin.h:
 extern "C" QObject *qt_plugin_instance();
-extern "C" QPluginMetaData qt_plugin_query_metadata();
+extern "C" QPluginMetaData qt_plugin_query_metadata_v2();
 class StaticPluginInstance{
 public:
     StaticPluginInstance() {
-        decltype(&qt_plugin_query_metadata) queryFn;
-        queryFn = []() {
-            // Static plugins don't carry the magic string (since Qt 6.3)
-            QPluginMetaData md = qt_plugin_query_metadata();
-            int delta = sizeof(QPluginMetaData::MagicString);
-            md.data = static_cast<const char *>(md.data) + delta;
-            md.size -= delta;
-            return md;
-        };
-        QStaticPlugin plugin(qt_plugin_instance, queryFn);
+        QStaticPlugin plugin(qt_plugin_instance, qt_plugin_query_metadata_v2);
         qRegisterStaticPluginFunction(plugin);
     }
 };