The __cplusplus macro does not work properly prior to MSVC2017 15.7 Preview 3: https://devblogs.microsoft.com/cppblog/msvc-now-correctly-reports-__cplusplus/

unvestigate · unvestigate · commit f15b8c7869a5 · 2020-03-19T12:31:55.000+02:00
diff --git a/include/behaviortree_cpp_v3/utils/make_unique.hpp b/include/behaviortree_cpp_v3/utils/make_unique.hpp
@@ -2,7 +2,7 @@
 
 #include <memory>
 
-#if defined(_MSC_VER) && __cplusplus == 201103L
+#if defined(_MSC_VER) && _MSC_VER >= 1900 // MSVC 2015 or newer.
 #  define MAKE_UNIQUE_DEFINED 1
 #endif
 
