Re: Storing pointer as a key in std::map

Carl Barron ha scritto:


You are assuming that every pointer is a custodial pointer to some heap
allocated object. Although that is a very common scenario, it's not
always the case. For example, a quick way to track all live instances of
a certain class is the following:

class A
{
   // let's assume no multi-threading for sake of exposition
   static std::set<A*> sRegistry;

public:
   A()
   {
     sRegistry.insert(this);
   }

   ~A()
   {
     sRegistry.erase(this);
   }
};

Notice that instances of A can be allocated either on the heap or on the
stack. You could also allow static instances, if you ensure A::sRegistry
is constructed before every instance of A (replacing sRegistry with a
static function+local static variable might help in that case).

HTH,

Ganesh

--
      [ See http://www.gotw.ca/resources/clcm.htm for info about ]
      [ comp.lang.c++.moderated. First time posters: Do this! ]