What is the difference between Boost smart pointers and std smart pointers?

Question

So, I\'d like to use smart pointers instead of raw and almost every topic on SO says about Boost library. But std has such things as std::auto_ptr and std::sh

Answer 1

Well, std::shared_ptr and boost:shared_ptr are both reference counting pointers. Instead std::auto_ptr works very differently. The difference between std::shared_ptr and boost:shared_ptr is very small and mostly historically. Before C++11 there was no std::shared_ptr and only boost:shared_ptr. When C++11 was designed, they took boost:shared_ptr as a model.

All your mentioned smart pointers have in common that they have their own mechanism to make sure that the lifetime management for points is done correctly. auto_ptr works so that if you have multiple instances of an auto_ptr then only one of them contains a pointer to the real object. Whenever you create an auto_ptr from another auto_ptr, then the new one will point to the object and the old one to NULL. On the other hand with shared_ptr there can be multiple shared_ptr instances that share the same object, only when the last one goes out of scope, only then the object is deleted..

In C++11 there is a similar pointer type to std::auto_ptr, namely std::unique_ptr, but there are some important differences, see also std::auto_ptr to std::unique_ptr.

References:

• http://www.cplusplus.com/reference/std/memory/auto_ptr/
• http://en.cppreference.com/w/cpp/memory/shared_ptr
• http://www.boost.org/doc/libs/1_52_0/libs/smart_ptr/shared_ptr.htm
• http://en.cppreference.com/w/cpp/memory/unique_ptr