diff --git a/eeschema/class_netlist_object.cpp b/eeschema/class_netlist_object.cpp
index ce3c2bbded..28cda6b3e3 100644
--- a/eeschema/class_netlist_object.cpp
+++ b/eeschema/class_netlist_object.cpp
@@ -81,7 +81,7 @@ void NETLIST_OBJECT::Show( std::ostream& out, int ndx )
 
     out << " <start " << m_Start << "/> <end " << m_End << "/>\n";
 
-    if( m_Label )
+    if( !m_Label.IsEmpty() )
         out << " <label>" << m_Label.mb_str() << "</label>\n";
 
     if( m_Comp )
diff --git a/eeschema/erc.cpp b/eeschema/erc.cpp
index cffbd49cb0..9efb32e6d2 100644
--- a/eeschema/erc.cpp
+++ b/eeschema/erc.cpp
@@ -174,8 +174,11 @@ static int MinimalReq[PIN_NMAX][PIN_NMAX] =
 /** Function TestDuplicateSheetNames( )
  * inside a given sheet, one cannot have sheets with duplicate names (file
  * names can be duplicated).
+ * @return the error count
+ * @param aCreateMarker: true = create error markers in schematic,
+ *                       false = calculate error count only
  */
-int TestDuplicateSheetNames()
+int TestDuplicateSheetNames(bool aCreateMarker)
 {
     int            err_count = 0;
     EDA_ScreenList ScreenList;      // Created the list of screen
@@ -203,17 +206,20 @@ int TestDuplicateSheetNames()
                         ( ( SCH_SHEET* ) item_to_test )-> m_SheetName )
                     == 0 )
                 {
-                    /* Create a new marker type ERC error*/
-                    SCH_MARKER* Marker = new SCH_MARKER();
-                    Marker->m_TimeStamp = GetTimeStamp();
-                    Marker->SetData( ERCE_DUPLICATE_SHEET_NAME,
-                                     ( (SCH_SHEET*) item_to_test )->m_Pos,
-                                     _( "Duplicate Sheet name" ),
-                                     ( (SCH_SHEET*) item_to_test )->m_Pos );
-                    Marker->SetMarkerType( MARK_ERC );
-                    Marker->SetErrorLevel( ERR );
-                    Marker->SetNext( Screen->EEDrawList );
-                    Screen->EEDrawList = Marker;
+                    if( aCreateMarker )
+                    {
+                        /* Create a new marker type ERC error*/
+                        SCH_MARKER* Marker = new SCH_MARKER();
+                        Marker->m_TimeStamp = GetTimeStamp();
+                        Marker->SetData( ERCE_DUPLICATE_SHEET_NAME,
+                                         ( (SCH_SHEET*) item_to_test )->m_Pos,
+                                         _( "Duplicate Sheet name" ),
+                                         ( (SCH_SHEET*) item_to_test )->m_Pos );
+                        Marker->SetMarkerType( MARK_ERC );
+                        Marker->SetErrorLevel( ERR );
+                        Marker->SetNext( Screen->EEDrawList );
+                        Screen->EEDrawList = Marker;
+                    }
                     err_count++;
                 }
             }
@@ -279,9 +285,8 @@ void DIALOG_ERC::TestErc( wxArrayString* aMessagesList )
      * inside a given sheet, one cannot have sheets with duplicate names (file
      * names can be duplicated).
      */
-    int errcnt = TestDuplicateSheetNames();
+    int errcnt = TestDuplicateSheetNames( true );
     g_EESchemaVar.NbErrorErc   += errcnt;
-    g_EESchemaVar.NbWarningErc += errcnt;
 
     m_Parent->BuildNetListBase();
 
@@ -290,7 +295,6 @@ void DIALOG_ERC::TestErc( wxArrayString* aMessagesList )
     for( unsigned ii = 0; ii < g_NetObjectslist.size(); ii++ )
         g_NetObjectslist[ii]->m_FlagOfConnection = UNCONNECTED;
 
-
     StartNet   = OldItem = 0;
     NetNbItems = 0;
     MinConn    = NOC;
diff --git a/eeschema/netlist_control.cpp b/eeschema/netlist_control.cpp
index 7c47e53bb9..67eb8e1f35 100644
--- a/eeschema/netlist_control.cpp
+++ b/eeschema/netlist_control.cpp
@@ -24,6 +24,8 @@
 #include "protos.h"
 #include "netlist_control.h"
 
+//Imported function:
+int TestDuplicateSheetNames(bool aCreateMarker);
 
 // ID for configuration:
 #define CUSTOM_NETLIST_TITLE   wxT( "CustomNetlistTitle" )
@@ -492,6 +494,13 @@ void WinEDA_NetlistFrame::GenNetlist( wxCommandEvent& event )
             return;
     }
 
+    // Test duplicate sheet names:
+    if( TestDuplicateSheetNames(false ) > 0 )
+    {
+        if( !IsOK( this, _( "Error: duplicate sheet names. Continue?" ) ) )
+            return;
+    }
+
     /* Cleanup the entire hierarchy */
     EDA_ScreenList ScreenList;
     for( SCH_SCREEN* screen = ScreenList.GetFirst();
diff --git a/pcbnew/zones_convert_brd_items_to_polygons.cpp b/pcbnew/zones_convert_brd_items_to_polygons.cpp
index e966854346..3c71300d21 100644
--- a/pcbnew/zones_convert_brd_items_to_polygons.cpp
+++ b/pcbnew/zones_convert_brd_items_to_polygons.cpp
@@ -216,11 +216,12 @@ void ZONE_CONTAINER::AddClearanceAreasPolygonsToPolysList( BOARD* aPcb )
     have_poly_to_substract = false;
 
     D_PAD dummyPad((MODULE*)NULL);
-
+    D_PAD * nextpad;
     for( MODULE* module = aPcb->m_Modules;  module;  module = module->Next() )
     {
-        for( D_PAD* pad = module->m_Pads; pad != NULL; pad = pad->Next() )
+        for( D_PAD* pad = module->m_Pads; pad != NULL; pad = nextpad )
         {
+            nextpad = pad->Next();  // pad pointer can be modified by next code, so calculate the next pad here
             if( !pad->IsOnLayer( GetLayer() ) )
             {   /* Test fo pads that are on top or bottom only and have a hole.
                  * There are curious pads but they can be used for some components that are inside the