Fixed a bug in the heap and nicer formatting for print_heap

kernel/debugging.c

@@ -33,6 +33,7 @@ void print_hex_bytes(void* bytes, size_t len)
 
 void print_heap()
 {
+    terminal_writestring("--START HEAP--\n");
     struct Heap_Block* current = global_heap.start;
 
     while (current != 0) {
@@ -55,4 +56,5 @@ void print_heap()
 
         current = current->next;
     }
+    terminal_writestring("--END HEAP--\n");
 }

kernel/heap.c

@@ -51,19 +51,34 @@ void* malloc(size_t size)
 void free(void *ptr)
 {
     struct Heap_Block* current = global_heap.start;
+
+    struct Heap_Block* first_unused;
+    bool found_unused = false;
+
     while (current->data != ptr) { 
+        if (!current->used && !found_unused) {
+            first_unused = current;
+            found_unused = true;
+        } else {
+            found_unused = false;
+        }
         current = current->next;
     }
 
+    if (!found_unused) {
+        first_unused = current;
+    }
+
     current->used = false;
 
     if (current->next == 0) {
         return;
     }
 
-    struct Heap_Block* start = current;
+    struct Heap_Block* start = first_unused;
+    current = start;
 
-    while (current->used == false && current != 0) {
+    while (current->used == false && current->next != 0) {
         current = current->next;
     }