From de2fcf0332003aeee2fbf2aa23a5bb02bf48e815 Mon Sep 17 00:00:00 2001
From: Robert Roebling <robert@roebling.de>
Date: Fri, 22 Aug 2008 09:18:30 +0000
Subject: [PATCH 1/1] #9854 (AddPendingEvent - protect during wxEvtHandler
 destruction)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@55167 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
---
 include/wx/event.h   |  2 ++
 src/common/event.cpp | 38 ++++++++++++++++++++++++++++++++------
 2 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/include/wx/event.h b/include/wx/event.h
index 9ca8341671..684d672419 100644
--- a/include/wx/event.h
+++ b/include/wx/event.h
@@ -2455,6 +2455,8 @@ protected:
 
     // Is event handler enabled?
     bool                m_enabled;
+    // Avoid adding events from another thread during dtor
+    bool                m_beingDeleted;
 
 
     // The user data: either an object which will be deleted by the container
diff --git a/src/common/event.cpp b/src/common/event.cpp
index 6c18e84338..9e8fbdf508 100644
--- a/src/common/event.cpp
+++ b/src/common/event.cpp
@@ -1032,6 +1032,8 @@ void wxEventHashTable::GrowEventTypeTable()
 
 wxEvtHandler::wxEvtHandler()
 {
+    m_beingDeleted = false;
+    
     m_nextHandler = (wxEvtHandler *) NULL;
     m_previousHandler = (wxEvtHandler *) NULL;
     m_enabled = true;
@@ -1045,6 +1047,8 @@ wxEvtHandler::wxEvtHandler()
 
 wxEvtHandler::~wxEvtHandler()
 {
+    m_beingDeleted = true;
+    
     // Takes itself out of the list of handlers
     if (m_previousHandler)
         m_previousHandler->m_nextHandler = m_nextHandler;
@@ -1062,7 +1066,6 @@ wxEvtHandler::~wxEvtHandler()
             wxDynamicEventTableEntry *entry = (wxDynamicEventTableEntry*)*it;
 
             // Remove ourselves from sink destructor notifications
-            // (this has usually been been done, in wxTrackable destructor)
             wxEvtHandler *eventSink = entry->m_eventSink;
             if ( eventSink )
             {
@@ -1083,8 +1086,17 @@ wxEvtHandler::~wxEvtHandler()
     };
 
     if (m_pendingEvents)
+    {
+        // At this time, we could still be used from other threads. 
+        // Continue to use sync objects.
+        wxENTER_CRIT_SECT( m_pendingEventsLock );
+        
         m_pendingEvents->DeleteContents(true);
-    delete m_pendingEvents;
+        delete m_pendingEvents;
+        m_pendingEvents = NULL;
+        
+        wxLEAVE_CRIT_SECT( m_pendingEventsLock );
+    }
 
     // Remove us from wxPendingEvents if necessary.
     if ( wxPendingEvents )
@@ -1132,6 +1144,9 @@ void wxEvtHandler::QueueEvent(wxEvent *event)
 {
     wxCHECK_RET( event, "NULL event can't be posted" );
 
+    // Catch the situation where destructor is already invoked (in another thread)
+    if( m_beingDeleted ) return;
+
     // 1) Add this event to our list of pending events
     wxENTER_CRIT_SECT( m_pendingEventsLock );
 
@@ -1163,10 +1178,21 @@ void wxEvtHandler::ProcessPendingEvents()
 {
     wxENTER_CRIT_SECT( m_pendingEventsLock );
 
-    // this method is only called by wxApp if this handler does have
-    // pending events
-    wxCHECK_RET( m_pendingEvents && !m_pendingEvents->IsEmpty(),
-                 "should have pending events if called" );
+    // This method is only called by wxApp if this handler does have
+    // pending events, but it happens occasionally when using multi-
+    // threading and we don't want a crash due to that.
+    if( !m_pendingEvents  )
+    {
+        wxLEAVE_CRIT_SECT( m_pendingEventsLock );
+        return;
+    }
+    
+    if( m_pendingEvents->IsEmpty() )
+    {
+        wxPendingEvents->DeleteObject(this);
+        wxLEAVE_CRIT_SECT( m_pendingEventsLock );
+        return;
+    }
 
     wxList::compatibility_iterator node = m_pendingEvents->GetFirst();
     wxEventPtr event(wx_static_cast(wxEvent *, node->GetData()));
-- 
2.47.2