Fixes: lp:1690840 (Pcbnew crashes when creating a drill file)

https://bugs.launchpad.net/kicad/+bug/1690840

pcbnew/exporters/gendrill_file_writer_base.cpp

@@ -50,14 +50,18 @@ static bool CmpHoleSorting( const HOLE_INFO& a, const HOLE_INFO& b )
 
     if( pada && padb )
     {
-        if( pada->GetParent()->GetReference().Cmp( padb->GetParent()->GetReference() ) != 0 )
-            return pada->GetParent()->GetReference().Cmp( padb->GetParent()->GetReference() ) < 0;
-    }
-    else if( pada || padb )
-        return true;
+        // cmp == 0 means the pads have the same parent, therfore the same reference
+        int cmp = pada->GetParent() - padb->GetParent();
 
-    // At this point, holes are via holes: sort by position
+        if( cmp )
+            return cmp < 0;
+    }
+    else if( pada || padb )     // in this case, other item is a via. Sort via first
+    {
+        return padb != nullptr;
+    }
 
+    // At this point, sort by position, as last sort criteria
     if( a.m_Hole_Pos.x != b.m_Hole_Pos.x )
         return a.m_Hole_Pos.x < b.m_Hole_Pos.x;
 

pcbnew/exporters/gendrill_gerber_writer.cpp

@@ -220,6 +220,7 @@ int GERBER_WRITER::createDrillFile( wxString& aFullFilename, bool aIsNpth,
     holes_count = 0;
 
     wxPoint hole_pos;
+    bool last_item_is_via = true;   // a flag to clear object attributes when a via hole is created.
 
     for( unsigned ii = 0; ii < m_holeListBuffer.size(); ii++ )
     {
@@ -233,9 +234,21 @@ int GERBER_WRITER::createDrillFile( wxString& aFullFilename, bool aIsNpth,
         GBR_METADATA gbr_metadata;
 
         if( dyn_cast<const VIA*>(hole_descr.m_ItemParent ) )
+        {
             gbr_metadata.SetApertureAttrib( GBR_APERTURE_METADATA::GBR_APERTURE_ATTRIB_VIADRILL );
+
+            if( !last_item_is_via )
+            {
+                // be sure the current object attribute is cleared for vias
+                plotter.EndBlock( NULL );
+            }
+
+            last_item_is_via = true;
+        }
         else if( dyn_cast<const D_PAD*>( hole_descr.m_ItemParent ) )
         {
+            last_item_is_via = false;
+
             if( hole_descr.m_Hole_Shape )
                 gbr_metadata.SetApertureAttrib( GBR_APERTURE_METADATA::GBR_APERTURE_ATTRIB_SLOTDRILL );
             else
@@ -243,7 +256,13 @@ int GERBER_WRITER::createDrillFile( wxString& aFullFilename, bool aIsNpth,
 
             // Add object attribute: component reference to pads (mainly usefull for users)
             const D_PAD* pad = dyn_cast<const D_PAD*>( hole_descr.m_ItemParent );
-            gbr_metadata.SetCmpReference( pad->GetParent()->GetReference() );
+            wxString ref = pad->GetParent()->GetReference();
+
+#if 0   // Set to 1 to force a dummy reference for the parent pad.
+            if( ref.IsEmpty() )
+                ref = "<undefinedref>";
+#endif
+            gbr_metadata.SetCmpReference( ref );
             gbr_metadata.SetNetAttribType( GBR_NETLIST_METADATA::GBR_NETINFO_CMP );
         }