From 92f6a34624ffb7635482c09a24a80983bb9c8043 Mon Sep 17 00:00:00 2001
From: Sefa Eyeoglu <contact@scrumplex.net>
Date: Mon, 23 Jan 2023 23:58:41 +0100
Subject: [PATCH] Merge pull request #758 from
 flowln/fix_process_events_backstab

---
 launcher/tasks/ConcurrentTask.cpp |  4 +--
 tests/Task_test.cpp               | 60 +++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/launcher/tasks/ConcurrentTask.cpp b/launcher/tasks/ConcurrentTask.cpp
index a890013ef..190d48d8f 100644
--- a/launcher/tasks/ConcurrentTask.cpp
+++ b/launcher/tasks/ConcurrentTask.cpp
@@ -110,14 +110,14 @@ void ConcurrentTask::startNext()
     setStepStatus(next->isMultiStep() ? next->getStepStatus() : next->getStatus());
     updateState();
 
+    QCoreApplication::processEvents();
+
     QMetaObject::invokeMethod(next.get(), &Task::start, Qt::QueuedConnection);
 
     // Allow going up the number of concurrent tasks in case of tasks being added in the middle of a running task.
     int num_starts = m_total_max_size - m_doing.size();
     for (int i = 0; i < num_starts; i++)
         QMetaObject::invokeMethod(this, &ConcurrentTask::startNext, Qt::QueuedConnection);
-
-    QCoreApplication::processEvents();
 }
 
 void ConcurrentTask::subTaskSucceeded(Task::Ptr task)
diff --git a/tests/Task_test.cpp b/tests/Task_test.cpp
index 80bba02fc..6649b7248 100644
--- a/tests/Task_test.cpp
+++ b/tests/Task_test.cpp
@@ -1,4 +1,6 @@
 #include <QTest>
+#include <QTimer>
+#include <QThread>
 
 #include <tasks/ConcurrentTask.h>
 #include <tasks/MultipleOptionsTask.h>
@@ -11,6 +13,9 @@ class BasicTask : public Task {
 
     friend class TaskTest;
 
+   public:
+    BasicTask(bool show_debug_log = true) : Task(nullptr, show_debug_log) {}
+
    private:
     void executeTask() override
     {
@@ -30,6 +35,42 @@ class BasicTask_MultiStep : public Task {
     void executeTask() override {};   
 };
 
+class BigConcurrentTask : public QThread {
+    Q_OBJECT
+
+    ConcurrentTask big_task;
+
+    void run() override
+    {
+        QTimer deadline;
+        deadline.setInterval(10000);
+        connect(&deadline, &QTimer::timeout, this, [this]{ passed_the_deadline = true; });
+        deadline.start();
+
+        // NOTE: Arbitrary value that manages to trigger a problem when there is one.
+        static const unsigned s_num_tasks = 1 << 14;
+        auto sub_tasks = new BasicTask*[s_num_tasks];
+
+        for (unsigned i = 0; i < s_num_tasks; i++) {
+            sub_tasks[i] = new BasicTask(false);
+            big_task.addTask(sub_tasks[i]);
+        }
+
+        big_task.run();
+
+        while (!big_task.isFinished() && !passed_the_deadline)
+            QCoreApplication::processEvents();
+
+        emit finished();
+    }
+
+   public:
+    bool passed_the_deadline = false;
+
+   signals:
+    void finished();
+};
+
 class TaskTest : public QObject {
     Q_OBJECT
 
@@ -183,6 +224,25 @@ class TaskTest : public QObject {
             return t.isFinished();
         }, 1000), "Task didn't finish as it should.");
     }
+
+    void test_stackOverflowInConcurrentTask()
+    {
+        QEventLoop loop;
+
+        auto thread = new BigConcurrentTask;
+        // NOTE: This is an arbitrary value, big enough to not cause problems on normal execution, but low enough
+        //       so that the number of tasks that needs to get ran to potentially cause a problem isn't too big.
+        thread->setStackSize(32 * 1024);
+
+        connect(thread, &BigConcurrentTask::finished, &loop, &QEventLoop::quit);
+
+        thread->start();
+
+        loop.exec();
+
+        QVERIFY(!thread->passed_the_deadline);
+        thread->deleteLater();
+    }
 };
 
 QTEST_GUILESS_MAIN(TaskTest)