智能指针与自动参考计数

Question

My knowledge on Objective-C and Automatic Reference Counting is very clear. And recently i am learning C++, Smart Pointer. I found that smart pointer and automatic reference counting are pretty much similar.

Though i couldn't find a side by side comparison(similarities and dissimilarities) on smart pointer and automatic reference counting with code sample/example using C++ and Objective-C. SO can anyone please give me a detailed explanation on this ?

EDIT: Here, by Smart Pointers I am indicating only std::shared_ptr , std::weak_ptr and std::unique_ptr .

Answer 1

Smart pointers don't necessarily have to be implemented in terms of reference counting.

The unique_ptr does not use any form of reference counting - when the unique_ptr goes out of scope the pointee is destroyed. Therefore the unique_ptr is considered to be as efficient as a raw pointer, which is nice: in cases where exclusive ownership can be used you have both automatic memory management and performance comparable to row pointer based implementation.

The shared_ptr is normally implemented using some form of reference counting, because it models shared ownership: when there are no more owners the resource is destroyed.