Hi, When I try to build "priority_queue_example.cpp" it get these warnings(and so errors) pointing to "priority_queue_example.h" on the line where my priority_queue is declared. The warnings are, 1> priority_queue_example.cpp 1>c:\Projects\lib\boost\boost\heap\detail\stable_heap.hpp(102): error C2220: warning treated as error - no 'object' file generated 1>c:\Projects\lib\boost\boost\heap\detail\stable_heap.hpp(102): warning C4100: 'rhs' : unreferenced formal parameter 1> c:\Projects\lib\boost\boost\heap\detail\stable_heap.hpp(102) : while compiling class template member function 'boost::heap::detail::size_holder::size_holder(const boost::heap::detail::size_holder &)' 1> c:\Projects\lib\boost\boost\heap\detail\stable_heap.hpp(189) : see reference to function template instantiation 'boost::heap::detail::size_holder::size_holder(const boost::heap::detail::size_holder &)' being compiled 1> c:\Projects\lib\boost\boost\heap\detail\stable_heap.hpp(151) : see reference to class template instantiation 'boost::heap::detail::size_holder' being compiled 1> c:\Projects\lib\boost\boost\heap\priority_queue.hpp(65) : see reference to class template instantiation 'boost::heap::detail::heap_base' being compiled 1> with 1> [ 1> T=myObject * 1> ] 1> c:\Projects\priority_queue_example.h(193) : see reference to class template instantiation 'boost::heap::priority_queue' being compiledcompare<ObjectPtrCompare>,boost::parameter::void_,boost::parameter::void My priority_queue is declared as, mutable boost::heap::priority_queue hp; Can you please help me fix this, I have been trying to for 2 days. Not sure what this means. This is my comparison class defined, struct myObjectPtrCompare { bool operator()(const myObject* lhs, const myObject* rhs) const { return (lhs->getProp() < rhs->getProp()); } }; Thanks!