Understanding Shared Pointer Control Blocks in C++

2023/08/22

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The article focuses on the different types of shared pointer control blocks in C++. It explains that shared pointers in the C++ standard library use a control block to manage the object lifetime. The control block has pure virtual methods, and derived classes determine how to dispose and delete the control block. If a shared_ptr takes responsibility for an already-constructed pointer, it adds a pointer to the managed object, which is deleted when the last strong reference is gone. The article also mentions the 'We know where you live' optimization, where the control block derives the buffer for holding the object. Debugging mainly involves checking the reference counts in the control block. The article provides bonus information about a different version of the control block for C++20 make_shared<T[]>. This article is relevant for developers who want to understand the inner workings of shared pointers in C++ and optimize their memory management.