Maxim Yegorushkin wrote:

I had difficulty storing and finding boost::intrusive_ptr<> in std::set<>. When I wanted to check if an arbitrary pointer value was in that set like:

struct some {/*...*/}; typedef boost::intrusive_ptr<some> some_ptr; typedef std::set<some_ptr> some_set; some_set set;

bool exists(some const* s) { return set.find(s) != set.end(); } void foo() { bool b = exists(reinterpret_cast<some*>(0xdeadbeaf)); // boom }

as std::set::find() requires a key value, it ended up with constructing the smart pointer from a bogus value trying to do add_ref() and then release() on that value which led to runtime errors.

If std::set<> had been able to use not a key value for find() but a key comparable value I would not have had any problems with that code.

I had similar problems with a conversion constructor getting invoked when I wanted to pass a pointer or value into std::set::find or std::multiset::count. That was one of the dificulties which led me to create flex_set and its related classes. Since flex_set does not require a temporary object, it also does not silently invoke a conversion constructor. Rich