BOARD_CONNECTED_ITEMs do not store net code anymore (m_NetCode field), instead net info is stored using a pointer to NETINFO_ITEM.

GetNet() refers to the net code stored in the NETINFO_ITEM. SetNet() finds an appropriate NETINFO_ITEM and uses it.
Removing GetNet() & SetNet() (and the whole net code idea) requires too many changes in the code (~250 references to the mentioned functions).
BOARD_CONNECTED_ITEMs by default get a pointer to NETINFO_ITEM that stores unconnected items. This requires for all BOARD_CONNECTED_ITEMs to have a parent (so BOARD* is accessible). The only orphaned item is BOARD_DESIGN_SETTINGS::m_Pad_Master, but it does not cause any issues so far.
Items that do not have access to a BOARD (do not have set parents) and therefore cannot get net assigned, by default get const static NETINFO_LIST::ORPHANED.

Performed tests:
- loaded .kicad_pcb, KiCad legacy board, Eagle 6.0 board, P-CAD board - all ok
- load a simple project, reload netlist after changing connections in eeschema - ok
- save & reload a board - ok, but still contain empty nets
- remove everything, restore with undo - ok
- remove everything, reload netlist - ok
- changing net names (all possibilites: empty->existing, empty->not existing, existing->empty, existing->not existing) - all ok
- zones: when net is changed to a net that does not have any nodes besides the zone itself, it does not get filled

include/class_board_item.h

@@ -83,8 +83,7 @@ protected:
 public:
 
     BOARD_ITEM( BOARD_ITEM* aParent, KICAD_T idtype ) :
-        EDA_ITEM( aParent, idtype )
+        EDA_ITEM( aParent, idtype ), m_Layer( FIRST_LAYER )
-        , m_Layer( FIRST_LAYER )
     {
     }
 

pcbnew/class_board.cpp

@@ -2571,7 +2571,8 @@ void BOARD::ReplaceNetlist( NETLIST& aNetlist, bool aDeleteSinglePadNets,
                         if( netinfo == NULL )
                         {
                             // It is a new net, we have to add it
-                            netinfo = new NETINFO_ITEM( this, net.GetNetName(), m_NetInfo.GetNetCount() );
+                            netinfo = new NETINFO_ITEM( this, net.GetNetName(),
+                                                        m_NetInfo.GetNetCount() );
                             m_NetInfo.AppendNet( netinfo );
                         }
 

pcbnew/class_board_connected_item.cpp

@@ -34,34 +34,50 @@
 #include <class_board.h>
 #include <class_board_item.h>
 
-
 BOARD_CONNECTED_ITEM::BOARD_CONNECTED_ITEM( BOARD_ITEM* aParent, KICAD_T idtype ) :
-    BOARD_ITEM( aParent, idtype ), m_NetCode( 0 ), m_Subnet( 0 ), m_ZoneSubnet( 0 )
+    BOARD_ITEM( aParent, idtype ), m_Subnet( 0 ), m_ZoneSubnet( 0 ),
+    m_netinfo( &NETINFO_LIST::ORPHANED )
 {
+    // The unconnected is set only in case the item belongs to a BOARD
+    SetNet( NETINFO_LIST::UNCONNECTED );
 }
 
 
 BOARD_CONNECTED_ITEM::BOARD_CONNECTED_ITEM( const BOARD_CONNECTED_ITEM& aItem ) :
-    BOARD_ITEM( aItem ), m_NetCode( aItem.m_NetCode ), m_Subnet( aItem.m_Subnet ),
+    BOARD_ITEM( aItem ), m_Subnet( aItem.m_Subnet ), m_ZoneSubnet( aItem.m_ZoneSubnet ),
-    m_ZoneSubnet( aItem.m_ZoneSubnet )
+    m_netinfo( aItem.m_netinfo )
 {
 }
 
 
+int BOARD_CONNECTED_ITEM::GetNet() const
+{
+    return m_netinfo->GetNet();
+}
+
+
+void BOARD_CONNECTED_ITEM::SetNet( int aNetCode )
+{
+    BOARD* board = GetBoard();
+    if( board )
+    {
+        m_netinfo = board->FindNet( aNetCode );
+
+        if( m_netinfo == NULL )
+            m_netinfo = board->FindNet( NETINFO_LIST::UNCONNECTED );
+    }
+}
+
+
 const wxString& BOARD_CONNECTED_ITEM::GetNetname() const
 {
-    BOARD* board = GetBoard();
+    return m_netinfo->GetNetname();
-    NETINFO_ITEM* netinfo = board->FindNet( m_NetCode );
-
-    return netinfo->GetNetname();
 }
 
 
 const wxString& BOARD_CONNECTED_ITEM::GetShortNetname() const
 {
-    NETINFO_ITEM* netinfo = GetBoard()->FindNet( m_NetCode );
+    return m_netinfo->GetShortNetname();
-
-    return netinfo->GetShortNetname();
 }
 
 

pcbnew/class_board_connected_item.h

@@ -33,6 +33,7 @@
 
 #include <class_board_item.h>
 
+class NETINFO_ITEM;
 class NETCLASS;
 class TRACK;
 class D_PAD;
@@ -54,8 +55,6 @@ public:
     std::vector<D_PAD*> m_PadsConnected;        // list of other pads connected to me
 
 private:
-    int         m_NetCode;      // Net number
-
     int         m_Subnet;       /* In rastnest routines : for the current net, block number
                                  * (number common to the current connected items found)
                                  */
@@ -63,6 +62,9 @@ private:
     int         m_ZoneSubnet;   // used in rastnest computations : for the current net,
                                 // handle cluster number in zone connection
 
+    /// Stores all informations about the net that item belongs to
+    const NETINFO_ITEM* m_netinfo;
+
 public:
     BOARD_CONNECTED_ITEM( BOARD_ITEM* aParent, KICAD_T idtype );
 
@@ -72,15 +74,15 @@ public:
      * Function GetNet
      * @return int - the net code.
      */
-    int GetNet() const
+    int GetNet() const;
-    {
-        return m_NetCode;
-    }
 
-    virtual void SetNet( int aNetCode )
+    /**
-    {
+     * Function SetNet
-        m_NetCode = aNetCode;
+     * sets net using a net code.
-    }
+     * @param aNetCode is a net code for the new net. It has to exist in NETINFO_LIST held by BOARD.
+     * Otherwise, item is assigned to the unconnected net.
+     */
+    void SetNet( int aNetCode );
 
     /**
      * Function GetSubNet
@@ -112,13 +114,13 @@ public:
 
     /**
      * Function GetNetname
-     * @return const wxString& - the full netname
+     * @return wxString - the full netname
      */
     const wxString& GetNetname() const;
 
     /**
      * Function GetShortNetname
-     * @return const wxString& - the short netname
+     * @return wxString - the short netname
      */
     const wxString& GetShortNetname() const;
 

pcbnew/class_board_design_settings.cpp

@@ -52,7 +52,7 @@
 
 
 BOARD_DESIGN_SETTINGS::BOARD_DESIGN_SETTINGS() :
-    m_Pad_Master( 0 )
+    m_Pad_Master( NULL )
 {
     m_EnabledLayers = ALL_LAYERS;               // All layers enabled at first.
                                                 // SetCopperLayerCount() will adjust this.

pcbnew/class_netinfo.h

@@ -202,6 +202,10 @@ public:
     ///> Constant that holds the unconnected net number
     static const int UNCONNECTED;
 
+    ///> NETINFO_ITEM meaning that there was no net assigned for an item, as there was no
+    ///> board storing net list available.
+    static const NETINFO_ITEM ORPHANED;
+
 #if defined(DEBUG)
     void Show() const;
 #endif

pcbnew/class_netinfolist.cpp

@@ -164,4 +164,5 @@ void NETINFO_LIST::buildPadsFullList()
 }
 
 
+const NETINFO_ITEM NETINFO_LIST::ORPHANED = NETINFO_ITEM( NULL, wxString( "orphaned" ), -1 );
 const int NETINFO_LIST::UNCONNECTED = 0;

pcbnew/class_zone.cpp

@@ -53,7 +53,6 @@
 ZONE_CONTAINER::ZONE_CONTAINER( BOARD* aBoard ) :
     BOARD_CONNECTED_ITEM( aBoard, PCB_ZONE_AREA_T )
 {
-    SetNet( -1 );                               // Net number for fast comparisons
     m_CornerSelection = -1;
     m_IsFilled = false;                         // fill status : true when the zone is filled
     m_FillMode = 0;                             // How to fill areas: 0 = use filled polygons, != 0 fill with segments

pcbnew/eagle_plugin.cpp

@@ -1879,7 +1879,7 @@ void EAGLE_PLUGIN::orientModuleText( MODULE* m, const EELEMENT& e,
 
 MODULE* EAGLE_PLUGIN::makeModule( CPTREE& aPackage, const string& aPkgName ) const
 {
-    std::auto_ptr<MODULE>   m( new MODULE( NULL ) );
+    std::auto_ptr<MODULE>   m( new MODULE( m_board ) );
 
     m->SetFPID( FPID( aPkgName ) );
 
@@ -2351,6 +2351,7 @@ void EAGLE_PLUGIN::loadSignals( CPTREE& aSignals )
 
         const string& nname = net->second.get<string>( "<xmlattr>.name" );
         wxString netName = FROM_UTF8( nname.c_str() );
+        m_board->AppendNet( new NETINFO_ITEM( m_board, netName, netCode ) );
 
         m_xpath->Value( nname.c_str() );
 
@@ -2555,7 +2556,7 @@ void EAGLE_PLUGIN::loadSignals( CPTREE& aSignals )
             // therefore omit this signal/net.
         }
         else
-            m_board->AppendNet( new NETINFO_ITEM( m_board, netName, netCode++ ) );
+            netCode++;
     }
 
     m_xpath->pop();     // "signals.signal"

pcbnew/pcb_parser.cpp

@@ -1731,7 +1731,7 @@ MODULE* PCB_PARSER::parseMODULE( wxArrayString* aInitialComments ) throw( IO_ERR
 
         case T_pad:
         {
-            D_PAD* pad = parseD_PAD();
+            D_PAD* pad = parseD_PAD( module.get() );
             wxPoint pt = pad->GetPos0();
             RotatePoint( &pt, module->GetOrientation() );
             pad->SetPosition( pt + module->GetPosition() );
@@ -2011,14 +2011,14 @@ EDGE_MODULE* PCB_PARSER::parseEDGE_MODULE() throw( IO_ERROR, PARSE_ERROR )
 }
 
 
-D_PAD* PCB_PARSER::parseD_PAD() throw( IO_ERROR, PARSE_ERROR )
+D_PAD* PCB_PARSER::parseD_PAD( MODULE* aParent ) throw( IO_ERROR, PARSE_ERROR )
 {
     wxCHECK_MSG( CurTok() == T_pad, NULL,
                  wxT( "Cannot parse " ) + GetTokenString( CurTok() ) + wxT( " as D_PAD." ) );
 
     wxSize sz;
     wxPoint pt;
-    std::auto_ptr< D_PAD > pad( new D_PAD( NULL ) );
+    std::auto_ptr< D_PAD > pad( new D_PAD( aParent ) );
 
     NeedSYMBOLorNUMBER();
     pad->SetPadName( FromUTF8() );

pcbnew/pcb_parser.h

@@ -99,7 +99,7 @@ class PCB_PARSER : public PCB_LEXER
     MODULE*         parseMODULE( wxArrayString* aInitialComments = 0 ) throw( IO_ERROR, PARSE_ERROR );
     TEXTE_MODULE*   parseTEXTE_MODULE() throw( IO_ERROR, PARSE_ERROR );
     EDGE_MODULE*    parseEDGE_MODULE() throw( IO_ERROR, PARSE_ERROR );
-    D_PAD*          parseD_PAD() throw( IO_ERROR, PARSE_ERROR );
+    D_PAD*          parseD_PAD( MODULE* aParent = NULL ) throw( IO_ERROR, PARSE_ERROR );
     TRACK*          parseTRACK() throw( IO_ERROR, PARSE_ERROR );
     SEGVIA*         parseSEGVIA() throw( IO_ERROR, PARSE_ERROR );
     ZONE_CONTAINER* parseZONE_CONTAINER() throw( IO_ERROR, PARSE_ERROR );