Eagle: Fix NULL-dereference on malformed Eagle files

Eagle files that are edited may be missing required data.  While we do
not need to handle these files, we do need to prevent segfaults in KiCad
when reading them.

eeschema/sch_eagle_plugin.cpp

@@ -469,8 +469,9 @@ void SCH_EAGLE_PLUGIN::loadDrawing( wxXmlNode* aDrawingNode )
 
     // wxXmlNode* grid = drawingChildren["grid"]
 
-    wxXmlNode* layers = drawingChildren["layers"];
+    auto layers = drawingChildren["layers"];
 
+    if( layers )
         loadLayerDefs( layers );
 
     // wxXmlNode* library = drawingChildren["library"]
@@ -479,7 +480,9 @@ void SCH_EAGLE_PLUGIN::loadDrawing( wxXmlNode* aDrawingNode )
 
 
     // Load schematic
-    loadSchematic( drawingChildren["schematic"] );
+    auto schematic = drawingChildren["schematic"];
+    if( schematic )
+        loadSchematic( schematic );
 }
 
 
@@ -488,7 +491,8 @@ void SCH_EAGLE_PLUGIN::countNets( wxXmlNode* aSchematicNode )
     // Map all children into a readable dictionary
     NODE_MAP schematicChildren = MapChildren( aSchematicNode );
     // Loop through all the sheets
-    wxXmlNode* sheetNode = schematicChildren["sheets"]->GetChildren();
+
+    wxXmlNode* sheetNode = getChildrenNodes( schematicChildren, "sheets" );
 
     while( sheetNode )
     {
@@ -519,8 +523,12 @@ void SCH_EAGLE_PLUGIN::loadSchematic( wxXmlNode* aSchematicNode )
 {
     // Map all children into a readable dictionary
     NODE_MAP schematicChildren = MapChildren( aSchematicNode );
+    auto partNode = getChildrenNodes( schematicChildren, "parts" );
+    auto libraryNode = getChildrenNodes( schematicChildren, "libraries" );
+    auto sheetNode = getChildrenNodes( schematicChildren, "sheets" );
 
-    wxXmlNode* partNode = schematicChildren["parts"]->GetChildren();
+    if( !partNode || !libraryNode || !sheetNode )
+        return;
 
     while( partNode )
     {
@@ -529,10 +537,7 @@ void SCH_EAGLE_PLUGIN::loadSchematic( wxXmlNode* aSchematicNode )
         partNode = partNode->GetNext();
     }
 
-
     // Loop through all the libraries
-    wxXmlNode* libraryNode = schematicChildren["libraries"]->GetChildren();
-
     while( libraryNode )
     {
         // Read the library name
@@ -553,9 +558,7 @@ void SCH_EAGLE_PLUGIN::loadSchematic( wxXmlNode* aSchematicNode )
     countNets( aSchematicNode );
 
     // Loop through all the sheets
-    wxXmlNode* sheetNode = schematicChildren["sheets"]->GetChildren();
-
-    int sheet_count = countChildren( schematicChildren["sheets"], "sheet" );
+    int sheet_count = countChildren( sheetNode->GetParent(), "sheet" );
 
     // If eagle schematic has multiple sheets then create corresponding subsheets on the root sheet
     if( sheet_count > 1 )
@@ -1264,7 +1267,7 @@ EAGLE_LIBRARY* SCH_EAGLE_PLUGIN::loadLibrary( wxXmlNode* aLibraryNode,
     NODE_MAP libraryChildren = MapChildren( aLibraryNode );
 
     // Loop through the symbols and load each of them
-    wxXmlNode* symbolNode = libraryChildren["symbols"]->GetChildren();
+    wxXmlNode* symbolNode = getChildrenNodes( libraryChildren, "symbols" );
 
     while( symbolNode )
     {
@@ -1274,7 +1277,7 @@ EAGLE_LIBRARY* SCH_EAGLE_PLUGIN::loadLibrary( wxXmlNode* aLibraryNode,
     }
 
     // Loop through the devicesets and load each of them
-    wxXmlNode* devicesetNode = libraryChildren["devicesets"]->GetChildren();
+    wxXmlNode* devicesetNode = getChildrenNodes( libraryChildren, "devicesets" );
 
     while( devicesetNode )
     {

pcbnew/eagle_plugin.cpp

@@ -377,14 +377,20 @@ void EAGLE_PLUGIN::loadAllSections( wxXmlNode* aDoc )
 
 void EAGLE_PLUGIN::loadDesignRules( wxXmlNode* aDesignRules )
 {
+    if( aDesignRules )
+    {
         m_xpath->push( "designrules" );
         m_rules->parse( aDesignRules );
         m_xpath->pop();     // "designrules"
+    }
 }
 
 
 void EAGLE_PLUGIN::loadLayerDefs( wxXmlNode* aLayers )
 {
+    if( !aLayers )
+        return;
+
     ELAYERS cu;  // copper layers
 
     // Get the first layer and iterate
@@ -456,6 +462,9 @@ void EAGLE_PLUGIN::loadLayerDefs( wxXmlNode* aLayers )
 
 void EAGLE_PLUGIN::loadPlain( wxXmlNode* aGraphics )
 {
+    if( !aGraphics )
+        return;
+
     m_xpath->push( "plain" );
 
     // Get the first graphic and iterate
@@ -780,11 +789,16 @@ void EAGLE_PLUGIN::loadPlain( wxXmlNode* aGraphics )
 
 void EAGLE_PLUGIN::loadLibrary( wxXmlNode* aLib, const wxString* aLibName )
 {
-    m_xpath->push( "packages" );
+    if( !aLib || !aLibName )
+        return;
 
     // library will have <xmlattr> node, skip that and get the single packages node
     wxXmlNode* packages = MapChildren( aLib )["packages"];
 
+    if( !packages )
+        return;
+
+    m_xpath->push( "packages" );
 
     // Create a MODULE for all the eagle packages, for use later via a copy constructor
     // to instantiate needed MODULES in our BOARD.  Save the MODULE templates in
@@ -836,6 +850,9 @@ void EAGLE_PLUGIN::loadLibrary( wxXmlNode* aLib, const wxString* aLibName )
 
 void EAGLE_PLUGIN::loadLibraries( wxXmlNode* aLibs )
 {
+    if( !aLibs )
+        return;
+
     m_xpath->push( "libraries.library", "name" );
 
     // Get the first library and iterate
@@ -856,6 +873,9 @@ void EAGLE_PLUGIN::loadLibraries( wxXmlNode* aLibs )
 
 void EAGLE_PLUGIN::loadElements( wxXmlNode* aElements )
 {
+    if( !aElements )
+        return;
+
     m_xpath->push( "elements.element", "name" );
 
     EATTR   name;