Fix living QObject member after shutdown of QCoreApplication

QHostInfoLookupManager has a QThreadPool as member.

QThreadPool is a QObject and must be deleted if the QCoreApplication
is being destroyed to release the underlying ThreadData.
A Q_GLOBAL_STATIC won't release any memory is not able to
manually release it.

Task-number: QTBUG-84234
Change-Id: I96be4601c3af38fa7c753a6f7acb8273ee277a27
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit 7e5a803c08c38e4fddc4338848768b7cfff4848f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 19 insertions, 2 deletions

diff --git a/src/network/kernel/qhostinfo.cpp b/src/network/kernel/qhostinfo.cpp
index 93be053ef3..33fb629899 100644
--- a/src/network/kernel/qhostinfo.cpp
+++ b/src/network/kernel/qhostinfo.cpp
@@ -72,8 +72,6 @@ QT_BEGIN_NAMESPACE
 
 //#define QHOSTINFO_DEBUG
 
-Q_GLOBAL_STATIC(QHostInfoLookupManager, theHostInfoLookupManager)
-
 namespace {
 struct ToBeLookedUpEquals {
     typedef bool result_type;
@@ -102,6 +100,25 @@ std::pair<OutputIt1, OutputIt2> separate_if(InputIt first, InputIt last, OutputI
     return std::make_pair(dest1, dest2);
 }
 
+QHostInfoLookupManager* theHostInfoLookupManager()
+{
+    static QHostInfoLookupManager* theManager = nullptr;
+    static QBasicMutex theMutex;
+
+    const QMutexLocker locker(&theMutex);
+    if (theManager == nullptr) {
+        theManager = new QHostInfoLookupManager();
+        Q_ASSERT(QCoreApplication::instance());
+        QObject::connect(QCoreApplication::instance(), &QCoreApplication::destroyed, [] {
+            const QMutexLocker locker(&theMutex);
+            delete theManager;
+            theManager = nullptr;
+        });
+    }
+
+    return theManager;
+}
+
 }
 
 /*