error loading object file when "usemtl" references an undefined material

SConstruct

@@ -1,6 +1,6 @@
 
 # vim:filetype=python
 
-env = Environment(LIBS = ['GL'], CXXFLAGS = ['-Wall'])
+env = Environment(LIBS = ['GL'], CXXFLAGS = ['-Wall', '-DGL_GLEXT_PROTOTYPES'])
 
 env.Program('driver', Glob('*.cc'))

WFObj.cc

@@ -1,6 +1,4 @@
 
-#define GL_GLEXT_PROTOTYPES
-
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -341,7 +339,7 @@ WFObj::VertexRef WFObj::readVertexRef(const std::string ref)
 void WFObj::loadMaterial(const std::string & name)
 {
     Buffer buff;
-    string path = (name[0] != '/') ? basePath(m_path) + name : name;
+    string path = resolvePath(name);
     if (!m_loadfile(path.c_str(), buff))
     {
         cerr << "WFObj: error: couldn't open material file '" << path << "'"
@@ -422,7 +420,7 @@ void WFObj::loadMaterial(const std::string & name)
         }
         else if (tokens[0] == "map_Kd")
         {
-            m_materials[mat_name].texture = loadTexture(tokens[1]);
+            m_materials[mat_name].texture = loadTexture(resolvePath(tokens[1]));
             if (m_materials[mat_name].texture != 0)
                 m_materials[mat_name].flags |= Material::TEXTURE_BIT;
         }
@@ -464,6 +462,12 @@ bool WFObj::buildVBO()
             it != m_faces.end();
             it++)
     {
+        if (m_materials.find(it->first) == m_materials.end())
+        {
+            cerr << "Material '" << it->first << "' referenced in '"
+                << m_path << "' is not defined." << endl;
+            return false;
+        }
         for (vector<Face>::iterator fit = it->second.begin();
                 fit != it->second.end();
                 fit++)
@@ -571,6 +575,11 @@ GLuint WFObj::loadTexture(const std::string & path)
     return id;
 }
 
+string WFObj::resolvePath(const string & name)
+{
+    return (name[0] != '/') ? basePath(m_path) + name : name;
+}
+
 bool WFObj::VertexRef::operator<(const VertexRef & other) const
 {
     if (vertex != other.vertex)

WFObj.h

@@ -19,7 +19,7 @@ public:
     class Buffer
     {
         public:
-            Buffer() : m_alloc(false) {}
+            Buffer() : m_alloc(false) {data = NULL; length = 0;}
             ~Buffer() { if (m_alloc) delete data; }
             uint8_t *data;
             size_t length;
@@ -116,6 +116,7 @@ protected:
     void loadMaterial(const std::string & name);
     bool buildVBO();
     GLuint loadTexture(const std::string & path);
+    std::string resolvePath(const std::string & name);
 
     /* variables */
     std::vector<Vertex> m_vertices[VERTEX_TYPES];