Why is `std::make_shared` More Efficient Than the `shared_ptr` Constructor in C ?

Understanding the Efficiency of std::make_shared vs. Normal Shared_ptr in C

Introduction:

In C , working with shared pointers is essential for proper memory management. Two common approaches for creating shared pointers are using std::make_shared and the traditional shared_ptr constructor. Understanding the difference between these methods is crucial for optimizing code efficiency. This article explores why std::make_shared is more efficient than using shared_ptr directly.

Heap Allocation Comparison:

The key difference lies in heap allocation. Std::make_shared performs a single heap allocation, allocating memory for both the control block (metadata) and the managed object. In contrast, using the shared_ptr constructor requires two heap allocations: one for the managed object and one for the control block.

Exceptional Handling:

Another advantage of std::make_shared is its better handling of exceptions. If an exception occurs during the construction of the managed object using new, the memory allocated for the object may be lost. This is because the raw pointer is not immediately passed to the shared_ptr constructor, leading to potential memory leaks. Using std::make_shared eliminates this issue as it creates both the control block and the object in a single operation, ensuring proper memory management even in case of exceptions.

Potential Disadvantage:

Despite its efficiency, std::make_shared has a potential disadvantage. Since it creates a single heap allocation for both the control block and the managed object, the memory for both cannot be deallocated independently. If weak pointers exist that reference the managed object, the control block will remain alive, even after the shared pointers have been deleted. This can lead to prolonged memory usage compared to using separate heap allocations for the control block and managed object.

Conclusion:

Std::make_shared offers a more efficient and exception-safe approach to creating shared pointers by performing a single heap allocation. This simplifies memory management and eliminates potential memory leaks. While std::make_shared may have a slight disadvantage in scenarios where independent deallocation is desired, its overall efficiency and exception handling make it the preferred choice for most C applications.

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