7 files changed, 19 insertions, 12 deletions
diff --git a/src/dbus/CMakeLists.txt b/src/dbus/CMakeLists.txt
index 9c3f6d23d2..a3ec0aac22 100644
--- a/src/dbus/CMakeLists.txt
+++ b/src/dbus/CMakeLists.txt
@@ -54,7 +54,6 @@ qt_internal_add_module(DBus
         Qt::Core
     PRIVATE_MODULE_INTERFACE
         Qt::CorePrivate
-    GENERATE_CPP_EXPORTS
 )
 
 # This file is included by qdbusargument.cpp
diff --git a/src/dbus/qdbusabstractadaptor.cpp b/src/dbus/qdbusabstractadaptor.cpp
index afe769fcd0..806a1b5f1f 100644
--- a/src/dbus/qdbusabstractadaptor.cpp
+++ b/src/dbus/qdbusabstractadaptor.cpp
@@ -8,7 +8,6 @@
 #include <QtCore/qcoreapplication.h>
 #include <QtCore/qmetaobject.h>
 #include <QtCore/qset.h>
-#include <QtCore/qtimer.h>
 #include <QtCore/qthread.h>
 
 #include "qdbusconnection.h"
diff --git a/src/dbus/qdbusextratypes.cpp b/src/dbus/qdbusextratypes.cpp
index 61f2075443..355a764e9c 100644
--- a/src/dbus/qdbusextratypes.cpp
+++ b/src/dbus/qdbusextratypes.cpp
@@ -13,6 +13,11 @@ QT_IMPL_METATYPE_EXTERN(QDBusObjectPath)
 QT_IMPL_METATYPE_EXTERN(QDBusSignature)
 
 #ifndef QT_NO_DEBUG_STREAM
+/*!
+    \fn QDebug QDBusObjectPath::operator<<(QDebug dbg, const QDBusObjectPath &path)
+    \since 6.8
+    Writes the contents of \a path to \a dbg.
+*/
 QDebug operator<<(QDebug dbg, const QDBusObjectPath &path)
 {
     QDebugStateSaver saver(dbg);
@@ -34,6 +39,8 @@ void QDBusSignature::doCheck()
     if (!QDBusUtil::isValidSignature(m_signature)) {
         qWarning("QDBusSignature: invalid signature \"%s\"", qPrintable(m_signature));
         m_signature.clear();
+    } else if (m_signature.isEmpty()) {
+        m_signature.detach();       // we need it to not be null
     }
 }
 
diff --git a/src/dbus/qdbusextratypes.h b/src/dbus/qdbusextratypes.h
index 1bc0f3086d..c548cbe7bb 100644
--- a/src/dbus/qdbusextratypes.h
+++ b/src/dbus/qdbusextratypes.h
@@ -38,6 +38,9 @@ public:
     operator QVariant() const;
 
 private:
+#ifndef QT_NO_DEBUG_STREAM
+    Q_DBUS_EXPORT friend QDebug operator<<(QDebug, const QDBusObjectPath &);
+#endif
     void doCheck();
 };
 Q_DECLARE_SHARED(QDBusObjectPath)
@@ -69,15 +72,15 @@ inline bool operator<(const QDBusObjectPath &lhs, const QDBusObjectPath &rhs)
 inline size_t qHash(const QDBusObjectPath &objectPath, size_t seed = 0)
 { return qHash(objectPath.path(), seed); }
 
-#ifndef QT_NO_DEBUG_STREAM
-Q_DBUS_EXPORT QDebug operator<<(QDebug, const QDBusObjectPath &);
-#endif
 
 class Q_DBUS_EXPORT QDBusSignature
 {
     QString m_signature;
 public:
-    QDBusSignature() noexcept : m_signature() {}
+    QDBusSignature() noexcept
+    {
+        m_signature.detach(); // mark non-null (empty signatures are valid)
+    }
     // compiler-generated copy/move constructor/assignment operators are ok!
     // compiler-generated destructor is ok!
 
diff --git a/src/dbus/qdbusintegrator.cpp b/src/dbus/qdbusintegrator.cpp
index 836562f496..1b03b7f6f6 100644
--- a/src/dbus/qdbusintegrator.cpp
+++ b/src/dbus/qdbusintegrator.cpp
@@ -11,7 +11,6 @@
 #include <qobject.h>
 #include <qsocketnotifier.h>
 #include <qstringlist.h>
-#include <qtimer.h>
 #include <qthread.h>
 #include <private/qlocking_p.h>
 #include <QtCore/qset.h>
diff --git a/src/dbus/qdbusmarshaller.cpp b/src/dbus/qdbusmarshaller.cpp
index b2ed2586fb..d1f1a41ab0 100644
--- a/src/dbus/qdbusmarshaller.cpp
+++ b/src/dbus/qdbusmarshaller.cpp
@@ -120,7 +120,7 @@ inline void QDBusMarshaller::append(const QDBusObjectPath &arg)
 inline void QDBusMarshaller::append(const QDBusSignature &arg)
 {
     QByteArray data = arg.signature().toUtf8();
-    if (!ba && data.isEmpty()) {
+    if (!ba && data.isNull()) {
         error("Invalid signature passed in arguments"_L1);
     } else {
         const char *cdata = data.constData();
diff --git a/src/dbus/qdbusutil.cpp b/src/dbus/qdbusutil.cpp
index 827418c487..78338aa054 100644
--- a/src/dbus/qdbusutil.cpp
+++ b/src/dbus/qdbusutil.cpp
@@ -512,14 +512,14 @@ namespace QDBusUtil
     bool isValidSignature(const QString &signature)
     {
         QByteArray ba = signature.toLatin1();
-        const char *data = ba.constData();
-        while (true) {
+        const char *data = ba.constBegin();
+        const char *end = ba.constEnd();
+        while (data != end) {
             data = validateSingleType(data);
             if (!data)
                 return false;
-            if (*data == '\0')
-                return true;
         }
+        return true;
     }
 
     /*!