Fix compilation issue for Boost 1.85

.pre-commit-config.yaml

@@ -26,7 +26,7 @@ repos:
               doc/doxygen-awesome.*
           )$
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.4.5
+    rev: v0.4.6
     hooks:
       - id: ruff-format
         exclude: doc/

CHANGELOG.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 
+### Fixed
+
+- Fix compilation issue for Boost 1.85 ([#2255](https://github.com/stack-of-tasks/pinocchio/pull/2255))
+
 ## [3.0.0] - 2024-05-27
 
 ### Added

src/parsers/mjcf/mjcf-graph.cpp

@@ -37,8 +37,9 @@ namespace pinocchio
           std::string path = el + ".<xmlattr>";
           if (parent.get_child_optional(path))
           {
-            ptree attr_parent = parent.get_child(path, ptree());
-            ptree attr_current = current.get_child(path, ptree());
+            const ptree default_value = ptree();
+            ptree attr_parent = parent.get_child(path, default_value);
+            const ptree & attr_current = current.get_child(path, default_value);
             // To only copy non existing attribute in current, we copy all current
             // attribute (replacing) into a parent copy then we replace current with the new
             // ptree