1 files changed, 39 insertions, 8 deletions

diff --git a/svl/source/notify/lstner.cxx b/svl/source/notify/lstner.cxx
index 4279e12f4a5c..0b3d2e9a3af5 100644
--- a/svl/source/notify/lstner.cxx
+++ b/svl/source/notify/lstner.cxx
@@ -21,17 +21,22 @@
 
 #include <svl/hint.hxx>
 #include <svl/SfxBroadcaster.hxx>
+#include <sal/backtrace.hxx>
 
 #include <algorithm>
 #include <cassert>
 #include <deque>
-
+#include <memory>
+#include <map>
 
 typedef std::deque<SfxBroadcaster*> SfxBroadcasterArr_Impl;
 
 struct SfxListener::Impl
 {
     SfxBroadcasterArr_Impl maBCs;
+#ifdef DBG_UTIL
+    std::map<SfxBroadcaster*, std::unique_ptr<BacktraceState>> maCallStacks;
+#endif
 };
 
 // simple ctor of class SfxListener
@@ -68,27 +73,47 @@ void SfxListener::RemoveBroadcaster_Impl( SfxBroadcaster& rBroadcaster )
     auto it = std::find( mpImpl->maBCs.begin(), mpImpl->maBCs.end(), &rBroadcaster );
     if (it != mpImpl->maBCs.end()) {
         mpImpl->maBCs.erase( it );
+#ifdef DBG_UTIL
+        mpImpl->maCallStacks.erase( &rBroadcaster );
+#endif
     }
 }
 
 
-// registers a specific SfxBroadcaster
 
-void SfxListener::StartListening( SfxBroadcaster& rBroadcaster, bool bPreventDups )
+/**
+ Registers a specific SfxBroadcaster.
+
+ Some code uses duplicates as a kind of ref-counting thing i.e. they add and remove listeners
+ on different code paths, and they only really stop listening when the last EndListening() is called.
+*/
+void SfxListener::StartListening( SfxBroadcaster& rBroadcaster, bool bPreventDuplicates )
 {
-    if ( !bPreventDups || !IsListening( rBroadcaster ) )
+    bool bListeningAlready = IsListening( rBroadcaster );
+
+#ifdef DBG_UTIL
+    if (bListeningAlready && !bPreventDuplicates)
+    {
+        auto f = mpImpl->maCallStacks.find( &rBroadcaster );
+        SAL_INFO("svl", "previous StartListening call came from: " << sal_backtrace_to_string(f->second.get()));
+    }
+#endif
+    assert(!(bListeningAlready && !bPreventDuplicates) && "duplicate listener, try building with DBG_UTIL to find the other insert site.");
+
+    if ( !bListeningAlready || !bPreventDuplicates )
     {
         rBroadcaster.AddListener(*this);
         mpImpl->maBCs.push_back( &rBroadcaster );
-
+#ifdef DBG_UTIL
+        mpImpl->maCallStacks.emplace( &rBroadcaster, sal_backtrace_get(10) );
+#endif
         assert(IsListening(rBroadcaster) && "StartListening failed");
     }
 }
 
-
 // unregisters a specific SfxBroadcaster
 
-void SfxListener::EndListening( SfxBroadcaster& rBroadcaster, bool bAllDups )
+void SfxListener::EndListening( SfxBroadcaster& rBroadcaster, bool bRemoveAllDuplicates )
 {
     SfxBroadcasterArr_Impl::iterator beginIt = mpImpl->maBCs.begin();
     do
@@ -100,8 +125,11 @@ void SfxListener::EndListening( SfxBroadcaster& rBroadcaster, bool bAllDups )
         }
         rBroadcaster.RemoveListener(*this);
         beginIt = mpImpl->maBCs.erase( it );
+#ifdef DBG_UTIL
+        mpImpl->maCallStacks.erase( &rBroadcaster );
+#endif
     }
-    while ( bAllDups );
+    while ( bRemoveAllDuplicates );
 }
 
 
@@ -116,6 +144,9 @@ void SfxListener::EndListeningAll()
         pBC->RemoveListener(*this);
         mpImpl->maBCs.pop_front();
     }
+#ifdef DBG_UTIL
+    mpImpl->maCallStacks.clear();
+#endif
 }