What are the characteristics of shared_ptr in C++?

In C++, shared_ptr is a smart pointer class used for managing dynamically allocated memory resources. It has the following characteristics:

1. Reference counting: shared_ptr uses reference counting to keep track of how many shared_ptr point to the same object. The counter increases each time a shared_ptr is created or copied. The counter decreases each time a shared_ptr is destroyed or reset. When the counter reaches zero, the shared_ptr automatically destroys the object and releases the memory.
2. Automatic resource release: shared_ptr uses the RAII (Resource Acquisition Is Initialization) technique to automatically release relevant resources when the object’s lifetime ends, eliminating the need for manually calling delete.
3. Ownership shared among multiple shared_ptr objects: shared_ptr allows multiple shared_ptr objects to share the same memory resource. The memory will only be released when all shared_ptr objects are destroyed or reset.
4. Custom Deleter: shared_ptr allows a specified deleter function to replace the default delete operation, enabling custom resource release.
5. shared_ptr can be a null pointer (nullptr) and it supports comparison with nullptr.
6. Copyable: shared_ptr can be copied, each copy increases the reference count. Memory is released when the last shared_ptr is destroyed.
7. Exception safety: the destructor and deleter of shared_ptr will work correctly even if an exception is thrown, preventing resource leaks.
8. Support for custom deleters: shared_ptr can release memory using a custom deleter, such as a custom function, function object, or lambda expression.

In general, shared_ptr provides a safe and convenient way to manage dynamically allocated memory in C++, allowing multiple shared_ptrs to share the same memory resource. It is an important memory management tool in C++.