Understanding the shared_ptr Constructor and enable_shared_from_this in C++

2023/08/16

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The article discusses the shared_ptr constructor and enable_shared_from_this in C++. When a class derives from std::enable_shared_from_this, it becomes a candidate for special treatment by shared_ptr. The shared_from_this() method produces a shared_ptr. The derived class gets a secret weak pointer called weak_this, which can be accessed using weak_from_this() and strong_from_this(). The shared_ptr constructor initializes this weak pointer when the control block is created. However, there are some restrictions and potential issues that developers should be aware of. For example, using make_shared to create the object can reduce the likelihood of issues. Additionally, forgetting to make the base class public or building a derivation hierarchy with multiple std::enable_shared_from_this base classes can cause problems. The article also explains how the shared_ptr constructor detects the presence of std::enable_shared_from_this and handles multiple base classes. This information is valuable for developers working with shared_ptr and enable_shared_from_this in C++.