Make most of QMetaTypeInterface constexpr

The only thing we need to modify at runtime is the typeId and that can
be mutable. This way we can have a constexpr ctor for QMetaType which
hopefully makes the importing and exporting of related symbols less
fickle.

On Windows we cannot make QMetaTypeForType constexpr as that leads to
mysterious errors in other places. Until we figure out why that is, we
just leave this class as non-constexpr.

This reveals that qcoreapplication.h and qvariant.h are using QDebug
without including it. We now get template instantiation errors. Include
qdebug.h to avoid that.

Change-Id: If1bf0437ada52459c59c6fa45bab3d22dfb0bc92
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 7 insertions, 7 deletions

diff --git a/src/corelib/kernel/qmetatype.cpp b/src/corelib/kernel/qmetatype.cpp
index c9a0a40cd0..d9de26141c 100644
--- a/src/corelib/kernel/qmetatype.cpp
+++ b/src/corelib/kernel/qmetatype.cpp
@@ -107,12 +107,12 @@ struct DefinedTypesFilter {
 struct QMetaTypeCustomRegistry
 {
     QReadWriteLock lock;
-    QList<QtPrivate::QMetaTypeInterface *> registry;
-    QHash<QByteArray, QtPrivate::QMetaTypeInterface *> aliases;
+    QList<const QtPrivate::QMetaTypeInterface *> registry;
+    QHash<QByteArray, const QtPrivate::QMetaTypeInterface *> aliases;
     // index of first empty (unregistered) type in registry, if any.
     int firstEmpty = 0;
 
-    int registerCustomType(QtPrivate::QMetaTypeInterface *ti)
+    int registerCustomType(const QtPrivate::QMetaTypeInterface *ti)
     {
         {
             QWriteLocker l(&lock);
@@ -168,7 +168,7 @@ struct QMetaTypeCustomRegistry
         firstEmpty = std::min(firstEmpty, idx);
     }
 
-    QtPrivate::QMetaTypeInterface *getCustomType(int id)
+    const QtPrivate::QMetaTypeInterface *getCustomType(int id)
     {
         QReadLocker l(&lock);
         return registry.value(id - QMetaType::User - 1);
@@ -847,7 +847,7 @@ static const struct : QMetaTypeModuleHelper
         return !(str.isEmpty() || str == LiteralWrapper("0") || str == LiteralWrapper("false"));
     }
 
-    QtPrivate::QMetaTypeInterface *interfaceForType(int type) const override {
+    const QtPrivate::QMetaTypeInterface *interfaceForType(int type) const override {
         switch (type) {
             QT_FOR_EACH_STATIC_PRIMITIVE_TYPE(QT_METATYPE_CONVERT_ID_TO_TYPE)
             QT_FOR_EACH_STATIC_PRIMITIVE_POINTER(QT_METATYPE_CONVERT_ID_TO_TYPE)
@@ -2898,9 +2898,9 @@ QMetaType QMetaType::fromName(QByteArrayView typeName)
     \sa Q_DECLARE_METATYPE(), QMetaType::type()
 */
 
-static QtPrivate::QMetaTypeInterface *interfaceForType(int typeId)
+static const QtPrivate::QMetaTypeInterface *interfaceForType(int typeId)
 {
-    QtPrivate::QMetaTypeInterface *iface = nullptr;
+    const QtPrivate::QMetaTypeInterface *iface = nullptr;
     if (typeId >= QMetaType::User) {
         if (auto reg = customTypeRegistry())
             iface = reg->getCustomType(typeId);