get that code compiling

include/cif++/category.hpp

@@ -182,7 +182,7 @@ class category
 
 	/// @brief Update the links in this category
 	/// @param db The enclosing @ref datablock
-	void update_links(datablock &db);
+	void update_links(const datablock &db);
 
 	/// @brief Return the global @ref validator for the data
 	/// @return The @ref validator or nullptr if not assigned

src/category.cpp

@@ -666,7 +666,7 @@ void category::set_validator(const validator *v, datablock &db)
 	update_links(db);
 }
 
-void category::update_links(datablock &db)
+void category::update_links(const datablock &db)
 {
 	m_child_links.clear();
 	m_parent_links.clear();
@@ -675,15 +675,15 @@ void category::update_links(datablock &db)
 	{
 		for (auto link : m_validator->get_links_for_parent(m_name))
 		{
-			auto childCat = db.get(link->m_child_category);
+			auto childCat = const_cast<category *>(db.get(link->m_child_category));
 			if (childCat == nullptr)
 				continue;
 			m_child_links.emplace_back(childCat, link);
 		}
 
 		for (auto link : m_validator->get_links_for_child(m_name))
 		{
-			auto parentCat = db.get(link->m_parent_category);
+			auto parentCat = const_cast<category *>(db.get(link->m_parent_category));
 			if (parentCat == nullptr)
 				continue;
 			m_parent_links.emplace_back(parentCat, link);

src/datablock.cpp

@@ -109,7 +109,7 @@ bool datablock::validate_links() const
 	bool result = true;
 
 	for (auto &cat : *this)
-		cat.update_links(*this);
+		const_cast<category &>(cat).update_links(*this);
 
 	for (auto &cat : *this)
 		result = cat.validate_links() and result;