Nuked the segfault on exit bug everyone was seeing. The material lib could

have multiple ptrs to individual entries (aliases) but the destructor was
trying to delete every ptr so it would delete already freed memory for aliases.
I implimented a simple ref counting scheme (similar to the plib mechanism) to
track references to material lib entries and only "delete" them when the last
reference is removed.

src/Objects/matlib.cxx

@@ -72,18 +72,6 @@ static bool local_file_exists( const string& path ) {
     } else {
 	return true;
     }
-
-#if 0
-    cout << path << " ";
-    FILE *fp = fopen( path.c_str(), "r" );
-    if ( fp == NULL ) {
-	cout << " doesn't exist\n";
-	return false;
-    } else {
-	cout << " exists\n";
-	return true;
-    }
-#endif
 }
 
 
@@ -123,6 +111,7 @@ bool FGMaterialLib::load( const string& mpath ) {
 	    FGNewMat *m = matlib[src_mat];
             if ( m != NULL ) {
                 matlib[dst_mat] = m;
+		m->ref();
             } else {
                 SG_LOG( SG_GENERAL, SG_ALERT,
                         "Bad material alias pointing to nonexistant material" );
@@ -139,6 +128,7 @@ bool FGMaterialLib::load( const string& mpath ) {
                 // create a pointer to a heap allocated copy of the structure
 		FGNewMat *m = new FGNewMat;
                 *m = tmp;
+		m->ref();
 
 		// build the ssgSimpleState
 		SGPath tex_path( globals->get_fg_root() );
@@ -277,9 +267,9 @@ FGMaterialLib::~FGMaterialLib ( void ) {
     // Free up all the material entries first
     for ( material_map_iterator it = begin(); it != end(); it++ ) {
 	FGNewMat *slot = it->second;
-        if ( slot != NULL ) {
+	slot->deRef();
+	if ( slot->getRef() <= 0 ) {
             delete slot;
-	    it->second = NULL;
         }
     }
 }

src/Objects/newmat.cxx

@@ -43,6 +43,7 @@ FGNewMat::FGNewMat ( void ) {
     wrapu = wrapv = 1;
     mipmap = 1;
     light_coverage = -1.0;
+    refcount = 0;
 }
 
 
@@ -67,6 +68,7 @@ FGNewMat::FGNewMat ( const string &mat_name, const string &tex_name )
     specular[0] = specular[1] = specular[2] = specular[3] = 1.0;
     emission[0] = emission[1] = emission[2] = emission[3] = 1.0;
     light_coverage = -1.0;
+    refcount = 0;
 }
 
 

src/Objects/newmat.hxx

@@ -92,6 +92,10 @@ private:
     // true if texture loading deferred, and not yet loaded
     bool texture_loaded;
 
+    // ref count so we can properly delete if we have multiple
+    // pointers to this record
+    int refcount;
+
 public:
 
     // Constructor
@@ -144,6 +148,10 @@ public:
 
     inline ssgStateSelector *get_state() const { return state; }
 
+    inline void ref() { refcount++; }
+    inline void deRef() { refcount--; }
+    inline int getRef() const { return refcount; }
+
     void dump_info();
 };