moc: fix const-init for Windows

References to __declspec(dllimport) is not a constant expression on
Windows, so we can't have a direct reference to a staticMetaObject.
Commit 9b8493314dd77f3e96b353187816bb7ef4dedbb5 fixed the Q_OBJECT parent
link (added in 5.14, kicked in for 6.0 with the ABI break), but commit
656d6f2a9b221dbd5adfc46262cb243e696d8d62 added links for Q_GADGETs too
without taking the need for Windows DLLs into account.

This change is a no-op everywhere but Windows. On Windows, since we
store the pointer to the indirect getter function, now you may get non-
null pointers from QMetaObject::superClass().

Change-Id: I6d3880c7d99d4fc494c8fffd16fab51aa255106e
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 688e8f63a2bb87469517166f90c50dec524f90c5)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 5 insertions, 5 deletions

diff --git a/src/corelib/kernel/qobjectdefs.h b/src/corelib/kernel/qobjectdefs.h
index 0fca56f703..8309e43d89 100644
--- a/src/corelib/kernel/qobjectdefs.h
+++ b/src/corelib/kernel/qobjectdefs.h
@@ -369,6 +369,7 @@ struct Q_CORE_EXPORT QMetaObject
     }
 
     struct SuperData {
+        using Getter = const QMetaObject *(*)();
         const QMetaObject *direct;
         SuperData() = default;
         constexpr SuperData(std::nullptr_t) : direct(nullptr) {}
@@ -377,7 +378,6 @@ struct Q_CORE_EXPORT QMetaObject
         constexpr const QMetaObject *operator->() const { return operator const QMetaObject *(); }
 
 #ifdef QT_NO_DATA_RELOCATION
-        using Getter = const QMetaObject *(*)();
         Getter indirect = nullptr;
         constexpr SuperData(Getter g) : direct(nullptr), indirect(g) {}
         constexpr operator const QMetaObject *() const
@@ -385,6 +385,7 @@ struct Q_CORE_EXPORT QMetaObject
         template <const QMetaObject &MO> static constexpr SuperData link()
         { return SuperData(QMetaObject::staticMetaObject<MO>); }
 #else
+        constexpr SuperData(Getter g) : direct(g()) {}
         constexpr operator const QMetaObject *() const
         { return direct; }
         template <const QMetaObject &MO> static constexpr SuperData link()
diff --git a/src/tools/moc/generator.cpp b/src/tools/moc/generator.cpp
index 701622862f..de939c2c48 100644
--- a/src/tools/moc/generator.cpp
+++ b/src/tools/moc/generator.cpp
@@ -489,16 +489,15 @@ void Generator::generateCode()
 //
 // Finally create and initialize the static meta object
 //
-    fprintf(out, "%sconst QMetaObject %s::staticMetaObject = { {\n",
-            // ### FIXME: gadgets are not constinit on Windows!
-            cdef->hasQGadget ? "" : "Q_CONSTINIT ", cdef->qualified.constData());
+    fprintf(out, "Q_CONSTINIT const QMetaObject %s::staticMetaObject = { {\n",
+            cdef->qualified.constData());
 
     if (isQObject)
         fprintf(out, "    nullptr,\n");
     else if (cdef->superclassList.size() && !cdef->hasQGadget && !cdef->hasQNamespace) // for qobject, we know the super class must have a static metaobject
         fprintf(out, "    QMetaObject::SuperData::link<%s::staticMetaObject>(),\n", purestSuperClass.constData());
     else if (cdef->superclassList.size()) // for gadgets we need to query at compile time for it
-        fprintf(out, "    QtPrivate::MetaObjectForType<%s>::value(),\n", purestSuperClass.constData());
+        fprintf(out, "    QtPrivate::MetaObjectForType<%s>::value,\n", purestSuperClass.constData());
     else
         fprintf(out, "    nullptr,\n");
     fprintf(out, "    qt_meta_stringdata_%s.offsetsAndSizes,\n"