Question

This crashes at runtime.

std::map<std::string, MyClass> myMap;
myValue = new MyClass();
myMap["myKey"] = *myValue;

I have 2 requirements:

1. That instances of MyClass are held on the heap (hence use of new);
2. That I be able to reference these via an associative array (hence use of std::Map).

Why can I not use the dereference operator succesfully in the example? How can I fulfill both at once?

PS. I’m using gcc.

Answer 1

If you lose the scope of myValue then it’s a memory leak. So it’s better to store the MyClass* in your map.

std::map<std::string, MyClass*> myMap;
myValue = new MyClass();
myMap["myKey"] = myValue;

In given example, also make sure you delete the element while erasing or removing from the map<>. You can use smart pointer (e.g. boost::shared_ptr) if you don’t want to worry about memory management.

Also, from your given example I don’t know why it should crash while dereferencing *myClass. Are you doing some weird stuff in copy constructor MyClass::MyClass(const MyClass&) ?