Added a check for recursive behavior trees while parsing

Author: Rockjack00

src/xml_parsing.cpp

@@ -10,6 +10,7 @@
 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
+#include <csignal>
 #include <cstdio>
 #include <cstring>
 #include <functional>
@@ -934,8 +935,17 @@ void BT::XMLParser::PImpl::recursivelyCreateSubtree(const std::string& tree_ID,
     }
     else  // special case: SubTreeNode
     {
-      auto new_bb = Blackboard::create(blackboard);
       const std::string subtree_ID = element->Attribute("ID");
+
+      // check for recursion in behavior tree
+      if(prefix.find(subtree_ID) != std::string::npos)
+      {
+        auto msg = StrCat("Recursive behavior trees are not supported. A cycle was found in ",
+                          "<Subtree ID=\"", subtree_ID, "\"> with prefix: ", prefix);
+        throw RuntimeError(msg);
+      }
+
+      auto new_bb = Blackboard::create(blackboard);
       std::unordered_map<std::string, std::string> subtree_remapping;
       bool do_autoremap = false;