问题
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::shared_ptr.
Why Boost? What is the difference?
It was a question not about difference of the implementation, but about reasons to use Boost pointers. I suppose, given answer, including date of answering and context, is reasonably useful. It helps to understand how Boost pointers were added to std.
回答1:
Basically Boost did shared_ptr first. You may note that many of the new container classes in C++11 were in Boost long ago. I would expect this pattern to continue with the next revisions of the C++ standard, too. Boost supports older C++ compilers that don't talk C++11, which is a big benefit.
Incidentally, std::auto_ptr is deprecated in C++11, which brings in std::shared_ptr and std::unique_ptr instead, which are both significantly more useful.
回答2:
Checkout the following stackoverflow questions:
- Difference between boost::shared_ptr and std::shared_ptr from the standard <memory> file
- Differences between different flavours of shared_ptr
回答3:
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
来源：https://stackoverflow.com/questions/13267908/what-is-the-difference-between-boost-smart-pointers-and-std-smart-pointers