Replace QDBusConnection::localMachineId with QSysInfo::machineUniqueId()

QSysInfo::machineUniqueId() was added in Qt 5.11 and is using DBus independent unique machine ids everywhere except on Linux. This prevents running into an assert in case DBus is not properly installed at a very early stage of the application without any chance to give the user a warning and handle it gracefully.

src/blackmisc/blackmisc.pro

@@ -69,6 +69,8 @@ SOURCES +=  *.cpp \
 
 win32 {
     LIBS *= -lShell32 -lDbghelp -lversion
+    # Remove the one below once the Reg functions are removed again from CIdentifier
+    LIBS *= -lAdvapi32
 }
 win32-g++ {
     LIBS *= -lpsapi

src/blackmisc/identifier.cpp

@@ -10,10 +10,18 @@
 #include "blackmisc/identifier.h"
 
 #include <QCoreApplication>
-#include <QDBusConnection>
 #include <QHostInfo>
+#include <QSysInfo>
 #include <QStringBuilder>
 
+#ifdef Q_OS_WIN
+#include <qt_windows.h>
+#endif
+
+#ifdef Q_OS_MAC
+#include <sys/sysctl.h>
+#endif
+
 //! \private
 const QString &cachedLocalHostName()
 {
@@ -21,12 +29,53 @@ const QString &cachedLocalHostName()
     return hostName;
 }
 
+enum {
+    UuidStringLen = sizeof("00000000-0000-0000-0000-000000000000")
+};
+
+QByteArray getMachineUniqueIdImpl()
+{
+    // TODO RR: Remove the workaround branches as soon as the following two changes are published in 5.12.2 (TBC)
+    // https://codereview.qt-project.org/#/c/249256
+    // https://codereview.qt-project.org/#/c/249399
+
+    QByteArray machineUniqueId;
+    #ifdef Q_OS_MAC
+        char uuid[UuidStringLen];
+        size_t uuidlen = sizeof(uuid);
+        int ret = sysctlbyname("kern.uuid", uuid, &uuidlen, nullptr, 0);
+        if (ret == 0 && uuidlen == sizeof(uuid))
+        {
+            machineUniqueId = QByteArray(uuid, uuidlen - 1);
+        }
+    #elif defined(Q_OS_WIN) && !defined(Q_OS_WINRT)
+        HKEY key = nullptr;
+        if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, L"SOFTWARE\\Microsoft\\Cryptography", 0, KEY_READ | KEY_WOW64_64KEY, &key) == ERROR_SUCCESS)
+        {
+            wchar_t buffer[UuidStringLen];
+            DWORD size = sizeof(buffer);
+            bool ok = (RegQueryValueEx(key, L"MachineGuid", nullptr, nullptr, reinterpret_cast<LPBYTE>(buffer), &size) == ERROR_SUCCESS);
+            RegCloseKey(key);
+            if (ok) { machineUniqueId = QStringView(buffer, (size - 1) / 2).toLatin1(); }
+        }
+    #else
+        machineUniqueId = QSysInfo::machineUniqueId();
+    #endif
+    return machineUniqueId;
+}
+
+QByteArray cachedMachineUniqueId()
+{
+    static const QByteArray machineUniqueId = getMachineUniqueIdImpl();
+    return machineUniqueId;
+}
+
 namespace BlackMisc
 {
     CIdentifier::CIdentifier(const QString &name)
         : ITimestampBased(QDateTime::currentMSecsSinceEpoch()),
           m_name(name.trimmed()),
-          m_machineIdBase64(QDBusConnection::localMachineId().toBase64()),
+          m_machineIdBase64(cachedMachineUniqueId().toBase64()),
           m_machineName(cachedLocalHostName()),
           m_processName(QCoreApplication::applicationName()),
           m_processId(QCoreApplication::applicationPid())
@@ -115,7 +164,7 @@ namespace BlackMisc
 
     bool CIdentifier::isFromLocalMachine() const
     {
-        return QDBusConnection::localMachineId() == getMachineId();
+        return cachedMachineUniqueId() == getMachineId();
     }
 
     bool CIdentifier::hasApplicationProcessId() const
@@ -175,4 +224,5 @@ namespace BlackMisc
     {
         CValueObject::setPropertyByIndex(index, variant);
     }
+
 } // ns

tests/blackmisc/testidentifier/testidentifier.cpp

@@ -32,6 +32,9 @@ namespace BlackMiscTest
     private slots:
         //! Identifier tests
         void identifierBasics();
+
+        //! Machine unique id tests
+        void machineUniqueId();
     };
 
     //! Test identifiable object
@@ -59,6 +62,12 @@ namespace BlackMiscTest
         QVERIFY2(oa.identifier().getName() == q.objectName(), "Names shall be equal");
     }
 
+    void CTestIdentifier::machineUniqueId()
+    {
+        CIdentifier o;
+        QVERIFY2(!o.getMachineId().isEmpty(), "Machine id shall never be empty! If this test failed on a supported platform, get a fallback solution!");
+    }
+
     CTestIdentifiable::CTestIdentifiable(QObject *nameObject) : CIdentifiable(nameObject)
     { }