在这种情况下，是否需要清空地图的内容，以避免内存泄漏

Question

Suppose I have a class as such

struct fooBar
{
   std::map<int, std::shared_ptr<foo> > mp_items;
   ~fooBar()
   { /* Destructor does nothing */ }
};

In the above case does the destructor have to mention mp_items.clear() or is it safe without that ?`

Answer 1

Since your map is containing shared_ptr, you don't need to take care of memory management. They will automatically be deleted when your map goes out of scope. One important thing to note over here is elements would be deleted only if there reference count reaches 0.

Answer 2

From cppreference :

 std::map::~map() 

Destructs the container. The destructors of the elements are called and the used storage is deallocated.

So no, there is no need to call clear() because the map's destructor does it for you.

The only case in which you'd ever have to deallocate memory in the destructor is if you allocated a data member with new / new[] and want its life to end when the object goes out of scope. In that case you would call delete / delete[] in the destructor.

However, note that there are memory management containers in the standard library that do it for you, like std::unique_ptr and std::shared_ptr among others.