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C++ Smart Pointers

1. Introduction to Smart Pointers

Understanding Pointers Dynamic memory allocation The Need For Smart Pointers

2. Unique Pointers

Introduction to Unique Pointers Moving Unique Pointers Application For Unique Pointers Passing Around Unique Pointers Methods of a Unique Pointer

3. Shared Pointers

Introduction to Shared Pointers Creating and Sharing Shared Pointers Circular References and Shared Pointers

4. Weak Pointers

Introduction to Weak Pointers Creating And Using Weak Pointers Breaking Circular References With Weak Pointers Important Weak Pointer Functions

5. Advanced topics

Providing Custom Deleters For Smart Pointers Performance Considerations With Smart Pointers Overview Shared vs Unique vs Weak Pointers

Creating and Sharing Shared Pointers

The Recommended Approach

The recommended way to create a shared pointer is through the std::make_shared function. This approach is generally more efficient and expressive compared to using new. It allocates memory for the object and the control block (reference count) in a single step. For example:

make_shared.h


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// Create a shared pointer to an integer
std::shared_ptr<int> p_int = std::make_shared<int>(42);

The above line allocates a dynamic integer and also initializes a shared pointer to it with a reference count of one.

The Discouraged Approach

You can also create shared pointers using new, but this method is discouraged because it is neither expressive nor efficient. The syntax for this approach requires you to pass the object to the shared pointer constructor.

creating_shared_pointer.h


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// Also creates a shared pointer to an integer   
std::shared_ptr<int> p_int(new int(42));

Allocating a dynamic integer and then passing it to the constructor of the shared pointer. However, the control block (reference count) will get initialized inside the constructor.

This means that we are doing two separate initializations, which is inefficient and error could be generated.

Passing Around Shared Pointers

Shared pointers are purpose-built for safe sharing. Let's explore a few ways we can pass them around.

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