Improved error handling for out of memory problems.

Linked.c

@@ -4,15 +4,10 @@
 
 #include "List.h"
 
-void FatalError ( const char *ErrorMessage ) {
-  printf ( "%s\n", ErrorMessage );
-  exit ( 1 );
-}
-
 void MakeList ( List *mylist, short (*Compare) ( const Element Data1, const Element Data2 ) )	{
 	mylist->RootNode = malloc ( sizeof( Node ) );
 	if ( mylist->RootNode == NULL )
-		FatalError ( "MakeList: Could not allocate a Node" );
+        return; /* out of memory */
 	mylist->Compare = Compare;
 	mylist->RootNode->Previous = NULL;
 	mylist->RootNode->Next = NULL;
@@ -50,12 +45,12 @@ Node *Get ( List *mylist, unsigned short index )	{
 	return GetPtr;
 }
 
-void InsertAt ( List *mylist, Element Data, Node *Pos )	{
+short InsertAt ( List *mylist, Element Data, Node *Pos )	{
 	Node *New;
 	New = malloc ( sizeof( Node ) );
 	if ( New == NULL )
-		FatalError ( "InsertAt: Could not allocate new Node" );
-	
+        return 0;
+
 	New->NodeElement = Data;
 	
 	if ( mylist->size == 0 )	{
@@ -64,7 +59,7 @@ void InsertAt ( List *mylist, Element Data, Node *Pos )	{
 		mylist->RootNode->Previous = New;
 		mylist->RootNode->Next = New;
 		mylist->size++;
-		return;
+		return 1;
 	}
 	
 	mylist->size++;
@@ -76,14 +71,15 @@ void InsertAt ( List *mylist, Element Data, Node *Pos )	{
 	}
 	if ( New->Previous != NULL )
 		New->Previous->Next = New;
+    return 1;
 }
 
 short IsEmpty ( List *mylist )	{
 	return mylist->size == 0;
 }
 
-void Push ( List *mylist, Element Data )	{
-	InsertAt ( mylist, Data, mylist->RootNode->Next );
+short Push ( List *mylist, Element Data )	{
+	return InsertAt ( mylist, Data, mylist->RootNode->Next );
 }
 
 Element Pop ( List *mylist )	{
@@ -100,8 +96,8 @@ Element Pop ( List *mylist )	{
 	return data;
 }
 
-void Enqueue ( List *mylist, Element Data )	{
-	InsertAt ( mylist, Data, mylist->RootNode );
+short Enqueue ( List *mylist, Element Data )	{
+	return InsertAt ( mylist, Data, mylist->RootNode );
 }
 
 Element Dequeue ( List *mylist )	{

List.h

@@ -25,17 +25,17 @@ Node *Find ( List *mylist, Element Data );
 /* Returns the index-th item in the List */
 Node *Get ( List *mylist, unsigned short index );
 /* Inserts Data in front of Node Pos into the List */
-void InsertAt ( List *mylist, Element Data, Node *Pos );
+short InsertAt ( List *mylist, Element Data, Node *Pos );
 
 /* Returns true if list size is 0 */
 short IsEmpty ( List *mylist );
 
 /* Pushes Data into mylist as if it were a stack */
-void Push ( List *mylist, Element Data );
+short Push ( List *mylist, Element Data );
 /* Pops the top Element off mylist, must free the returned Element when done */
 Element Pop ( List *mylist );
 /* Enqueues Data as if List were a queue */
-void Enqueue ( List *mylist, Element Data );
+short Enqueue ( List *mylist, Element Data );
 /* Dequeues the front Element off mylist, must free the returned Element when done */
 Element Dequeue ( List *mylist );
 

Makefile

@@ -12,4 +12,4 @@ $(SRCS):
 	$(CC) $(CFLAGS) -o $@ $*.c
 
 clean:
-	@rm *.o
+	@rm *.o $(O_TARGET)

main.c

@@ -39,6 +39,13 @@ short CompareString ( const Element Data1, const Element Data2 )	{
 	return strcmp ( Data1, Data2 );
 }
 
+void OutOfMemory ( List *mylist )    {
+    printf ( "Ran out of memory!\n" );
+    if ( mylist != NULL && mylist->RootNode != NULL )
+        MakeEmpty ( mylist );
+    exit ( 1 );
+}
+
 #ifdef USE_TI92PLUS
 
 void _main ( void )
@@ -59,6 +66,8 @@ int main ( void )
 #endif
 	
  	MakeList ( &mylist, CompareString ); 
+    if ( mylist.RootNode == NULL )
+        OutOfMemory ( &mylist );
 	PrintList ( &mylist );
 
 	for ( i = 0; i < 10; i++ )	{
@@ -72,15 +81,24 @@ int main ( void )
 	tmp = malloc ( sizeof( Element ) * 3 );
 	sprintf ( tmp, "%d", 20 );
 	FindPtr = Find ( &mylist, (Element)"3" );
-	InsertAt ( &mylist, tmp, FindPtr ); 
+	if ( !InsertAt ( &mylist, tmp, FindPtr ) )  {
+        free ( tmp );
+        OutOfMemory ( &mylist );
+    }
 	
 	tmp = malloc ( sizeof( Element ) * 4 );
 	sprintf ( tmp, "%s", "FOO" );
-	Enqueue ( &mylist, tmp ); 
+	if ( !Enqueue ( &mylist, tmp ) )    {
+        free ( tmp );
+        OutOfMemory ( &mylist );
+    }
 	
 	tmp = malloc ( sizeof( Element ) * 4 );
 	sprintf ( tmp, "%s", "BAR" );
-	Enqueue ( &mylist, tmp );
+	if ( !Enqueue ( &mylist, tmp ) )    {
+        free ( tmp );
+        OutOfMemory ( &mylist );
+    }
 
 	PrintList ( &mylist );
 	MakeEmpty ( &mylist );