QMetaType: don't use global relocations to the lambdas and structures

The way the Qt 6.0 QMetaTypeInterface was designed, using a static
inline variable in a template, would normally require the linker and
dynamic linker to merge all copies and choose a single copy as the
official one. But because of hidden visibility and of Windows DLLs,
QMetaType already copes with multiple copies NOT getting merged. So we
may as well ask the linkers not to bother and use simpler, local
relocations to find those symbols.

They are all supposed to still be equivalent and it's an ODR violation
if they're not.

The Apple ld64 linker complains if you use this type of global
relocation:

 ld: warning: direct access in function
  [...]
   to global weak symbol
   'QtPrivate::QMetaTypeInterfaceWrapper<int>::metaType'

Fixes: QTBUG-93471
Pick-to: 6.3 6.4
Change-Id: Id0fb9ab0089845ee8843fffd16f98a10aa719434
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 8 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype2.cpp b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype2.cpp
index 11dc593ebb..265ec3095f 100644
--- a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype2.cpp
+++ b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype2.cpp
@@ -522,6 +522,14 @@ void tst_QMetaType::operatorEqAcrossLibs()
     QCOMPARE(QByteArray(lib2Type.name()), QByteArray(localType.name()));
     QCOMPARE(lib1Type, localType);
     QCOMPARE(lib2Type, localType);
+
+#if !defined(Q_OS_WIN) && !defined(Q_OS_INTEGRITY)
+    if (actualTypeId < QMetaType::FirstGuiType && actualTypeId != QMetaType::Void) {
+        // for built-in QtCore types, we expect the interfaces to be the same too
+        QCOMPARE(lib1Iface, localIface);
+        QCOMPARE(lib2Iface, localIface);
+    }
+#endif
 }
 
 class WithPrivateDTor {