diff --git a/Makefile b/Makefile
index 3fb2e7c..498ab38 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 CC=gcc
-CFLAGS=-Wall -pedantic -g -DUNIX_HOST -DDEBUG_HEAP
+CFLAGS=-Wall -pedantic -g -DUNIX_HOST
 LIBS=#-lm
 
 TARGET	= picoc
diff --git a/expression.c b/expression.c
index f36bcf1..56c445a 100644
--- a/expression.c
+++ b/expression.c
@@ -258,11 +258,15 @@ void ExpressionStackPushLValue(struct ParseState *Parser, struct ExpressionStack
 void ExpressionStackPushDereference(struct ParseState *Parser, struct ExpressionStack **StackTop, struct Value *DereferenceValue)
 {
     struct Value *DerefVal;
+    struct Value *ValueLoc;
     int Offset;
     struct ValueType *DerefType;
     int DerefIsLValue;
     void *DerefDataLoc = VariableDereferencePointer(Parser, DereferenceValue, &DerefVal, &Offset, &DerefType, &DerefIsLValue);
-    struct Value *ValueLoc = VariableAllocValueFromExistingData(Parser, DerefType, (union AnyValue *)DerefDataLoc, DerefIsLValue, DerefVal);
+    if (DerefDataLoc == NULL)
+        ProgramFail(Parser, "NULL pointer dereference");
+
+    ValueLoc = VariableAllocValueFromExistingData(Parser, DerefType, (union AnyValue *)DerefDataLoc, DerefIsLValue, DerefVal);
     ExpressionStackPushValueNode(Parser, StackTop, ValueLoc);
 }
 
@@ -372,6 +376,7 @@ void ExpressionAssign(struct ParseState *Parser, struct Value *DestValue, struct
 void ExpressionPrefixOperator(struct ParseState *Parser, struct ExpressionStack **StackTop, enum LexToken Op, struct Value *TopValue)
 {
     struct Value *Result;
+    union AnyValue *ValPtr;
 
     if (Parser->Mode != RunModeRun)
     {
@@ -387,8 +392,9 @@ void ExpressionPrefixOperator(struct ParseState *Parser, struct ExpressionStack
             if (!TopValue->IsLValue)
                 ProgramFail(Parser, "can't get the address of this");
 
+	    ValPtr = TopValue->Val;
             Result = VariableAllocValueFromType(Parser, TypeGetMatching(Parser, TopValue->Typ, TypePointer, 0, StrEmpty), FALSE, NULL, FALSE);
-            Result->Val->NativePointer = TopValue->Val;
+            Result->Val->NativePointer = (void *)ValPtr;
             ExpressionStackPushValueNode(Parser, StackTop, Result);
             break;
 
@@ -762,7 +768,8 @@ void ExpressionStackCollapse(struct ParseState *Parser, struct ExpressionStack *
                     TopValue = TopStackNode->Val;
                     
                     /* pop the value and then the prefix operator - assume they'll still be there until we're done */
-                    HeapPopStack(TopOperatorNode, sizeof(struct ExpressionStack)*2 + sizeof(struct Value) + TypeStackSizeValue(TopValue));
+                    HeapPopStack(NULL, sizeof(struct ExpressionStack) + sizeof(struct Value) + TypeStackSizeValue(TopValue));
+                    HeapPopStack(TopOperatorNode, sizeof(struct ExpressionStack));
                     *StackTop = TopOperatorNode->Next;
                     
                     /* do the prefix operation */
@@ -775,7 +782,8 @@ void ExpressionStackCollapse(struct ParseState *Parser, struct ExpressionStack *
                     TopValue = TopStackNode->Next->Val;
                     
                     /* pop the postfix operator and then the value - assume they'll still be there until we're done */
-                    HeapPopStack(TopValue, sizeof(struct ExpressionStack)*2 + sizeof(struct Value) + TypeStackSizeValue(TopValue));
+                    HeapPopStack(NULL, sizeof(struct ExpressionStack));
+                    HeapPopStack(TopValue, sizeof(struct ExpressionStack) + sizeof(struct Value) + TypeStackSizeValue(TopValue));
                     *StackTop = TopStackNode->Next->Next;
 
                     /* do the postfix operation */
@@ -791,7 +799,9 @@ void ExpressionStackCollapse(struct ParseState *Parser, struct ExpressionStack *
                         BottomValue = TopOperatorNode->Next->Val;
                         
                         /* pop a value, the operator and another value - assume they'll still be there until we're done */
-                        HeapPopStack(BottomValue, sizeof(struct ExpressionStack)*3 + sizeof(struct Value)*2 + TypeStackSizeValue(TopValue) + TypeStackSizeValue(BottomValue));
+                        HeapPopStack(NULL, sizeof(struct ExpressionStack) + sizeof(struct Value) + TypeStackSizeValue(TopValue));
+                        HeapPopStack(NULL, sizeof(struct ExpressionStack));
+                        HeapPopStack(BottomValue, sizeof(struct ExpressionStack) + sizeof(struct Value) + TypeStackSizeValue(BottomValue));
                         *StackTop = TopOperatorNode->Next->Next;
                         
                         /* do the infix operation */
diff --git a/heap.c b/heap.c
index 5b907b7..5658908 100644
--- a/heap.c
+++ b/heap.c
@@ -86,7 +86,7 @@ int HeapPopStack(void *Addr, int Size)
     printf("HeapPopStack(0x%lx, %ld) back to 0x%lx\n", (unsigned long)Addr, (unsigned long)MEM_ALIGN(Size), (unsigned long)HeapStackTop - ToLose);
 #endif
     HeapStackTop = (void *)((char *)HeapStackTop - ToLose);
-    assert(HeapStackTop == Addr);
+    assert(Addr == NULL || HeapStackTop == Addr);
     
     return TRUE;
 }
@@ -99,7 +99,7 @@ void HeapPushStackFrame()
 #endif
     *(void **)HeapStackTop = StackFrame;
     StackFrame = HeapStackTop;
-    HeapStackTop = (void *)((char *)HeapStackTop + sizeof(void *));
+    HeapStackTop = (void *)((char *)HeapStackTop + MEM_ALIGN(sizeof(void *)));
 }
 
 /* pop the current stack frame, freeing all memory in the frame. can return NULL */
@@ -219,7 +219,7 @@ void HeapFreeMem(void *Mem)
     int Bucket = MemNode->Size >> 2;
     
 #ifdef DEBUG_HEAP
-    printf("HeapFreeMem(%lx)\n", (unsigned long)Mem);
+    printf("HeapFreeMem(0x%lx)\n", (unsigned long)Mem);
 #endif
     assert((unsigned long)Mem >= (unsigned long)&HeapMemory[0] && (unsigned char *)Mem - &HeapMemory[0] < HEAP_SIZE);
     assert(MemNode->Size < HEAP_SIZE && MemNode->Size > 0);
diff --git a/type.c b/type.c
index 84eef58..ea87491 100644
--- a/type.c
+++ b/type.c
@@ -73,7 +73,7 @@ int TypeStackSizeValue(struct Value *Val)
 int TypeSizeValue(struct Value *Val)
 {
     if (Val->Typ->Base == TypeChar || Val->Typ->Base == TypeShort)
-        return sizeof(int);     /* allow some extra room for type extension to int */
+        return sizeof(void *);     /* allow some extra room for type extension */
     else if (Val->Typ->Base != TypeArray)
         return Val->Typ->Sizeof;
     else
@@ -84,7 +84,7 @@ int TypeSizeValue(struct Value *Val)
 int TypeSize(struct ValueType *Typ, int ArraySize, int Compact)
 {
     if ( (Typ->Base == TypeChar || Typ->Base == TypeShort) && !Compact)
-        return sizeof(int);     /* allow some extra room for type extension to int */
+        return sizeof(void *);     /* allow some extra room for type extension */
     else if (Typ->Base != TypeArray)
         return Typ->Sizeof;
     else