read_graphml: use a proper message handler

Using null_message_handlert may hide errors.

Author: tautschnig

src/xmllang/graphml.cpp

@@ -177,9 +177,9 @@ static bool build_graph(
 bool read_graphml(
   std::istream &is,
   graphmlt &dest,
-  graphmlt::node_indext &entry)
+  graphmlt::node_indext &entry,
+  message_handlert &message_handler)
 {
-  null_message_handlert message_handler;
   xmlt xml;
 
   if(parse_xml(is, "", message_handler, xml))
@@ -191,9 +191,9 @@ bool read_graphml(
 bool read_graphml(
   const std::string &filename,
   graphmlt &dest,
-  graphmlt::node_indext &entry)
+  graphmlt::node_indext &entry,
+  message_handlert &message_handler)
 {
-  null_message_handlert message_handler;
   xmlt xml;
 
   if(parse_xml(filename, message_handler, xml))

src/xmllang/graphml.h

@@ -19,6 +19,8 @@ Author: Michael Tautschnig, mt@eecs.qmul.ac.uk
 #include <util/graph.h>
 #include <util/xml.h>
 
+class message_handlert;
+
 struct xml_edget
 {
   xmlt xml_node;
@@ -68,11 +70,13 @@ class graphmlt:public grapht<xml_graph_nodet>
 bool read_graphml(
   std::istream &is,
   graphmlt &dest,
-  graphmlt::node_indext &entry);
+  graphmlt::node_indext &entry,
+  message_handlert &message_handler);
 bool read_graphml(
   const std::string &filename,
   graphmlt &dest,
-  graphmlt::node_indext &entry);
+  graphmlt::node_indext &entry,
+  message_handlert &message_handler);
 
 bool write_graphml(const graphmlt &src, std::ostream &os);