Why should C++ programmers minimize use of ' new '?

Indeed, as C++ programmers, we should minimize the direct use of the new keyword for dynamic memory allocation. This is due to several core reasons:

1. Memory Management Complexity

Direct use of new requires manual memory management, including proper use of delete for deallocation. This increases development complexity and can lead to errors such as memory leaks and double frees. For instance, if you forget to release memory allocated via new, it remains unrecoverable, potentially causing the program's memory usage to grow indefinitely, known as a memory leak.

2. Exception Safety Issues

In C++, if an exception is thrown during the constructor call rather than caught after new, the allocated memory is not automatically released, leading to memory leaks. For example, if you allocate an object array and the constructor throws an exception, previously constructed objects are not destroyed, resulting in complex memory management issues.

3. Resource Management (RAII)

C++ promotes the Resource Acquisition Is Initialization (RAII) principle, where resource lifetimes are managed through object lifetimes. Using smart pointers (such as std::unique_ptr and std::shared_ptr) automatically manages memory; when the smart pointer object goes out of scope, it deletes the associated memory. This significantly simplifies memory management and exception handling.

4. Standard Library Containers

C++'s standard library provides containers like std::vector and std::map, which internally manage memory, avoiding direct use of new. They offer flexible and efficient memory management, supporting automatic expansion and contraction of elements.

5. Modern C++ Practices

Since C++11, the standard has strongly recommended using smart pointers and other resource management classes instead of raw pointers. This is because they provide safer resource management and reduce various errors associated with raw pointers.

Example Illustration

Suppose we need to create an object array. Using raw pointers and new might look like this:

cpp
MyClass *arr = new MyClass[10];
// If an exception occurs or early return is needed, manually delete arr
delete[] arr;

Using modern C++, we can do this:

cpp
std::vector<MyClass> arr(10);
// Automatically manages memory, no manual release needed

1. Memory Leak Risk

After allocating memory with new, the programmer must manually release it using delete at the appropriate time. If memory is not released, it leads to memory leaks. Memory leaks gradually consume system memory resources, potentially causing performance degradation or crashes in the program or system.

Example:

cpp
int *array = new int[100];  // Allocate memory
// Program forgets to release memory

2. Management Complexity

Managing dynamic memory is more complex than static storage (e.g., automatic variables on the stack). Managing new and delete requires careful attention, especially when exceptions are thrown or multiple return paths exist, where errors are easy to occur.

Example:

cpp
int process() {
    int *ptr = new int;
    if (some_condition_fails()) {
        delete ptr;  // Must manually release before each return point
        return -1;
    }
    // Other logic
    delete ptr;  // Release again
    return 0;
}

3. Performance Issues

new and delete involve operating system memory management, which may be slower than stack memory (automatic allocation and deallocation). Frequent use of new and delete in performance-critical applications can impact overall program performance.

4. Modern C++ Resource Management

Modern C++ recommends using smart pointers like std::unique_ptr and std::shared_ptr for managing dynamic memory, which automatically release memory and reduce memory leak risks. Additionally, C++'s standard library provides containers like std::vector and std::string, which internally manage memory, eliminating the need for direct new usage.

Example:

cpp
#include <memory>
#include <vector>

void example() {
    std::unique_ptr<int> smartPtr(new int(10));  // Automatically manages memory
    std::vector<int> myVector;  // Automatically expands and manages memory
    myVector.push_back(42);
}

Conclusion

Although new remains a necessary tool in C++—especially when explicit control over object lifetimes is required—leveraging modern C++ resource management tools and techniques can significantly reduce direct new usage, enhancing code safety, maintainability, and performance. Opt for RAII (Resource Acquisition Is Initialization), smart pointers, and standard library containers to simplify resource management and avoid common pitfalls.