NBT: Only call free() if we allocated it

src/nbt/NBT.cpp

@@ -160,18 +160,19 @@ namespace NBT
     //==================================================
 
     CompoundTag::CompoundTag(const char *filename)
-        : CompoundTag(nbt_parse_path(filename))
+        : CompoundTag(nbt_parse_path(filename), true) // m_isRoot = true, this calls malloc
     {
     }
 
     CompoundTag::CompoundTag(const void* data, size_t length)
-        : CompoundTag(nbt_parse_compressed(data, length))
+        : CompoundTag(nbt_parse_compressed(data, length), true) // m_isRoot = true, this calls malloc
     {
     }
 
     CompoundTag::~CompoundTag()
     {
-        nbt_free(m_node);
+        if (m_isRoot)
+            nbt_free(m_node);
     }
 
     const Tag CompoundTag::operator[](const char *name) const

src/nbt/NBT.h

@@ -135,12 +135,17 @@ namespace NBT
     // A Compound Tag is an unordered list of named tags
     class CompoundTag : public Tag
     {
+        // only true if the tree was allocated by constructor
+        const bool m_isRoot;
+        
+        CompoundTag(nbt_node* node, bool isRoot) : Tag(node), m_isRoot(false) {}
     public:
-        CompoundTag(nbt_node* node) : Tag(node) {}
+        CompoundTag(nbt_node* node) : CompoundTag(node, false) {}
 
+        // Read tree from file 
         CompoundTag(const char* filename);
 
-        // Read a compound tag from compressed data
+        // Read tree from compressed data
         CompoundTag(const void* data, size_t length);
 
         ~CompoundTag();