feat: added PooledThreadExecutor::WaitUntilStopped function

Author: František Bořánek

src/aws-cpp-sdk-core/include/aws/core/utils/threading/Executor.h

@@ -99,6 +99,11 @@ namespace Aws
                 PooledThreadExecutor(PooledThreadExecutor&&) = delete;
                 PooledThreadExecutor& operator =(PooledThreadExecutor&&) = delete;
 
+                /**
+                * Call to ensure the threadpool can be safely destroyed. It blocks until all threads finished.
+                */
+                void WaitUntilStopped();
+
             protected:
                 bool SubmitToThread(std::function<void()>&&) override;
 
@@ -109,6 +114,7 @@ namespace Aws
                 Aws::Vector<ThreadTask*> m_threadTaskHandles;
                 size_t m_poolSize;
                 OverflowPolicy m_overflowPolicy;
+                bool m_stopped{false};
 
                 /**
                  * Once you call this, you are responsible for freeing the memory pointed to by task.

src/aws-cpp-sdk-core/source/utils/threading/Executor.cpp

@@ -89,6 +89,15 @@ PooledThreadExecutor::PooledThreadExecutor(size_t poolSize, OverflowPolicy overf
 
 PooledThreadExecutor::~PooledThreadExecutor()
 {
+    WaitUntilStopped();
+}
+
+void PooledThreadExecutor::WaitUntilStopped()
+{
+    {
+        std::lock_guard<std::mutex> locker(m_queueLock);
+        m_stopped = true;
+    }
     for(auto threadTask : m_threadTaskHandles)
     {
         threadTask->StopProcessingWork();
@@ -100,6 +109,7 @@ PooledThreadExecutor::~PooledThreadExecutor()
     {
         Aws::Delete(threadTask);
     }
+    m_threadTaskHandles.clear();
 
     while(m_tasks.size() > 0)
     {
@@ -111,7 +121,6 @@ PooledThreadExecutor::~PooledThreadExecutor()
             Aws::Delete(fn);
         }
     }
-
 }
 
 bool PooledThreadExecutor::SubmitToThread(std::function<void()>&& fn)
@@ -122,7 +131,7 @@ bool PooledThreadExecutor::SubmitToThread(std::function<void()>&& fn)
     {
         std::lock_guard<std::mutex> locker(m_queueLock);
 
-        if (m_overflowPolicy == OverflowPolicy::REJECT_IMMEDIATELY && m_tasks.size() >= m_poolSize)
+        if (m_stopped || (m_overflowPolicy == OverflowPolicy::REJECT_IMMEDIATELY && m_tasks.size() >= m_poolSize))
         {
             Aws::Delete(fnCpy);
             return false;