Merge pull request #115 from ashtum/delete-get_child-overloads-that-accept-temporaries

Prevent calls to get_child with temporary default values

Author: pdimov

include/boost/property_tree/ptree.hpp

@@ -270,6 +270,10 @@ namespace boost { namespace property_tree
         const self_type &get_child(const path_type &path,
                                    const self_type &default_value) const;
 
+        /** Prevents calls to get_child with temporary default values */
+        void get_child(const path_type &path,
+                       const self_type &&default_value) const = delete;
+
         /** Get the child at the given path, or return boost::null. */
         optional<self_type &> get_child_optional(const path_type &path);
 

test/test_property_tree.cpp

@@ -9,6 +9,7 @@
 // ----------------------------------------------------------------------------
 #include "test_utils.hpp"
 #include <boost/any.hpp>
+#include <boost/mp11.hpp>
 #include <boost/range.hpp>
 #include <list>
 #include <cmath>
@@ -67,6 +68,11 @@ struct any_translator
     }
 };
 
+// Checks the validity of calling get_child with a default value type
+template<class P, class C, class D>
+using get_child_accepts_default_of_type = decltype(
+    std::declval<P>().get_child(std::declval<const C*>(), std::declval<D>()));
+
 namespace boost { namespace property_tree {
     template <typename E>
     struct translator_between<boost::any, E>

test/test_property_tree.hpp

@@ -820,14 +820,27 @@ void test_get_child_put_child(PTREE *)
     BOOST_TEST(cpt2.get_child(T("k2.k")) == pt);
 
     // Do correct extractions via get_child (default value version)
-    BOOST_TEST(pt1.get_child(T("k1"), PTREE(T("def"))) != PTREE(T("def")));
-    BOOST_TEST(pt1.get_child(T("k2.k"), PTREE(T("def"))) != PTREE(T("def")));
-    BOOST_TEST(pt2.get_child(T("k1"), PTREE(T("def"))) == pt);
-    BOOST_TEST(pt2.get_child(T("k2.k"), PTREE(T("def"))) == pt);
-    BOOST_TEST(cpt1.get_child(T("k1"), PTREE(T("def"))) != PTREE(T("def")));
-    BOOST_TEST(cpt1.get_child(T("k2.k"), PTREE(T("def"))) != PTREE(T("def")));
-    BOOST_TEST(cpt2.get_child(T("k1"), PTREE(T("def"))) == pt);
-    BOOST_TEST(cpt2.get_child(T("k2.k"), PTREE(T("def"))) == pt);
+    PTREE dflt(T("def"));
+    BOOST_TEST(pt1.get_child(T("k1"), dflt) != dflt);
+    BOOST_TEST(pt1.get_child(T("k2.k"), dflt) != dflt);
+    BOOST_TEST(pt2.get_child(T("k1"), dflt) == pt);
+    BOOST_TEST(pt2.get_child(T("k2.k"), dflt) == pt);
+    BOOST_TEST(cpt1.get_child(T("k1"), dflt) != dflt);
+    BOOST_TEST(cpt1.get_child(T("k2.k"), dflt) != dflt);
+    BOOST_TEST(cpt2.get_child(T("k1"), dflt) == pt);
+    BOOST_TEST(cpt2.get_child(T("k2.k"), dflt) == pt);
+
+    // Ensure that get_child does not compile when using temporaries as the default value.
+    BOOST_TEST((!boost::mp11::mp_valid<get_child_accepts_default_of_type, const PTREE&, CHTYPE, PTREE>::value));
+    BOOST_TEST((!boost::mp11::mp_valid<get_child_accepts_default_of_type, const PTREE&, CHTYPE, const PTREE>::value));
+    BOOST_TEST((!boost::mp11::mp_valid<get_child_accepts_default_of_type, PTREE&, CHTYPE, PTREE>::value));
+    BOOST_TEST((!boost::mp11::mp_valid<get_child_accepts_default_of_type, PTREE&, CHTYPE, const PTREE>::value));
+
+    // Test get_child_accepts_default_of_type itself
+    BOOST_TEST((boost::mp11::mp_valid<get_child_accepts_default_of_type, const PTREE&, CHTYPE, PTREE&>::value));
+    BOOST_TEST((boost::mp11::mp_valid<get_child_accepts_default_of_type, const PTREE&, CHTYPE, const PTREE&>::value));
+    BOOST_TEST((boost::mp11::mp_valid<get_child_accepts_default_of_type, PTREE&, CHTYPE, PTREE&>::value));
+    BOOST_TEST((boost::mp11::mp_valid<get_child_accepts_default_of_type, PTREE&, CHTYPE, const PTREE&>::value));
 
     // Do correct extractions via get_child (optional version)
     boost::optional<PTREE &> opt;