From 90d96766aff31e65fd5d0f9dbbd2f527f45f0cec Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Mon, 3 Jul 2023 08:05:03 +0200
Subject: [PATCH] QEventLoopLocker: defend against nullptr arguments

The class would previosuly produce a crash when the QEventLoop* or the
QThread* were nullptr or if no QCoreApplication existed. We want,
however, the out-of-line constructors of the class to be noexcept, and
for that, they should neither allocation nor have preconditions. The
former is for another patch; this patch deals with the latter.

[ChangeLog][QtCore][QEventLoopLocker] Is now a no-op on nullptr
QEventLoop*, QThread*, QCoreApplication::instance() (was: crash).

Task-number: QTBUG-114793
Change-Id: I4246f74008df6ad7fcbfde56403397b065fbe861
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 3748b194d4de790540aa74db8d65b602e097f415)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/kernel/qeventloop.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/corelib/kernel/qeventloop.cpp b/src/corelib/kernel/qeventloop.cpp
index edde9492f88..f348708aad0 100644
--- a/src/corelib/kernel/qeventloop.cpp
+++ b/src/corelib/kernel/qeventloop.cpp
@@ -407,6 +407,8 @@ void QEventLoopLocker::visit(Func f) const
 {
     using Type = QEventLoopLockerPrivate::Type;
     const auto ptr = d_ptr->pointer();
+    if (!ptr)
+        return;
     switch (d_ptr->type()) {
     case Type::EventLoop:   return f(static_cast<QEventLoopPrivate *>(ptr));
     case Type::Thread:      return f(static_cast<QThreadPrivate *>(ptr));