Why You Should Use std__make_unique and std__make_shared

Using std::make_unique and std::make_shared in C++ offers significant advantages in terms of memory management, code clarity, and performance. These utility functions are part of the C++11 standard and are recommended over directly using new to allocate objects. Here’s why you should consider using them in your C++ code:

1. Memory Safety

Both std::make_unique and std::make_shared help to prevent memory leaks by ensuring proper resource management through automatic memory deallocation when the object goes out of scope. These smart pointers automatically manage the lifetime of objects, preventing the programmer from forgetting to call delete or from accidentally creating memory leaks.

• std::make_unique creates a std::unique_ptr, which ensures exclusive ownership of the allocated memory. When the unique_ptr goes out of scope, the memory is automatically freed.

• std::make_shared creates a std::shared_ptr, which keeps track of how many pointers share ownership of the object. Once the last shared pointer goes out of scope, the object is destroyed.

2. Improved Exception Safety

When using new directly to allocate memory, exceptions can lead to memory leaks if the delete statement is not properly called. With std::make_unique and std::make_shared, memory is freed automatically in case of exceptions, making your code more exception-safe.

Consider this scenario with new:

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SomeClass* ptr = new SomeClass();
// Exception thrown here
// Memory is not released, leading to a memory leak.

With std::make_unique:

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auto ptr = std::make_unique<SomeClass>();
// No need to manually delete, memory is managed automatically.

3. Cleaner and More Readable Code

Using std::make_unique and std::make_shared results in simpler, more readable code. These functions handle the allocation and initialization of objects in a concise and consistent manner.

• std::make_unique<T>(args...) creates a unique pointer that points to an object of type T, forwarding the arguments to the constructor of T.

• std::make_shared<T>(args...) works similarly but returns a shared pointer. This eliminates the need to manually use new or deal with pointer ownership issues directly.

Example with new:

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auto ptr = new SomeClass(arg1, arg2);

Example with std::make_unique:

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auto ptr = std::make_unique<SomeClass>(arg1, arg2);

4. Reduced Risk of Dangling Pointers

When using new directly, there is a risk of creating dangling pointers—pointers that point to memory that has already been deallocated. With std::make_unique and std::make_shared, this risk is reduced because they manage the memory lifetime for you.

In the case of std::unique_ptr, once the unique pointer is destroyed, the memory is automatically deallocated, and there’s no possibility of the pointer dangling.

In the case of std::shared_ptr, the memory is freed only when the last shared_ptr to the object is destroyed, ensuring that no dangling pointers exist as long as there is a shared pointer in scope.

5. Efficiency and Performance

Using std::make_unique and std::make_shared can be more efficient than using raw new operators because these functions avoid extra overhead associated with manual memory management.

• std::make_shared can be more efficient than manually creating a std::shared_ptr with new because it only requires a single memory allocation for both the object and its reference count. This can reduce memory fragmentation and the overhead of separate allocations.

• std::make_unique is even more efficient, as it does not involve any shared ownership, and therefore, it has no need for a reference counter, making it a lighter-weight option compared to std::shared_ptr.

6. Prevention of Multiple Ownership Mistakes

The direct use of new and delete often leads to mistakes when managing the ownership of dynamically allocated objects. With std::make_unique, the object has a single owner, and with std::make_shared, ownership is shared between multiple owners, but only as long as the reference count is maintained correctly. This prevents accidental double-deletion or other pointer-related issues.

7. Cleaner Memory Management with std::make_shared

While std::unique_ptr ensures exclusive ownership of a dynamically allocated object, std::shared_ptr is useful when multiple parts of the program need to share ownership of an object. By using std::make_shared, you eliminate the risk of forgetting to update the reference count or forgetting to release the object.

Example of std::make_shared:

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auto ptr = std::make_shared<SomeClass>(arg1, arg2);

This provides a shared pointer without needing to worry about manual memory management and reference counting.

8. Better Integration with Modern C++ Libraries

Many modern C++ libraries and APIs are designed with std::shared_ptr and std::unique_ptr in mind. Using std::make_shared and std::make_unique ensures that your code integrates smoothly with these libraries and their memory management schemes.

For example, if you’re using the C++ Standard Library containers such as std::vector, std::map, etc., which can store smart pointers, it’s easier and safer to work with smart pointers created by std::make_unique or std::make_shared.

9. Simplifying Object Creation

Both std::make_unique and std::make_shared are capable of forwarding arguments to the constructor of the object, simplifying object creation and reducing boilerplate code. This is particularly useful when working with complex object types or when passing arguments to the constructor.

Example:

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auto ptr = std::make_unique<SomeClass>(arg1, arg2);

Here, std::make_unique forwards arg1 and arg2 to the constructor of SomeClass.

Conclusion

std::make_unique and std::make_shared provide numerous advantages in C++ programming, including safety, readability, efficiency, and better memory management. By adopting these utilities in your code, you ensure that memory is managed automatically, exceptions are handled properly, and ownership semantics are clear and consistent. This leads to more reliable, maintainable, and less error-prone code. Whether you need exclusive ownership with std::make_unique or shared ownership with std::make_shared, these functions make your life as a C++ developer easier and your code safer.