Do you know about placement new operator?

Yes, I know. Placement new allows you to place an object at an already allocated memory address without using standard heap allocation.

Main features:

• Does not allocate memory itself, uses the provided address.
• Calls the object's constructor at the specified address.
• You must manage the object's lifetime yourself (call the destructor).
• Often used with memory pools or pre-allocated memory.

#include <iostream>
#include <new> // for placement new

class MyClass {
public:
    int value;
    MyClass(int v) : value(v) {
        std::cout << "Constructor called, value: " << value << std::endl;
    }
    ~MyClass() {
        std::cout << "Destructor called, value: " << value << std::endl;
    }
};

int main() {
    // Allocate memory manually
    char buffer[sizeof(MyClass)];

    // Use placement new to create object in buffer
    MyClass* obj = new (buffer) MyClass(10);

    // Access the object
    std::cout << "Object value accessed: " << obj->value << std::endl;

    // Call destructor explicitly
    obj->~MyClass();

    // No need to free memory, as it was allocated on the stack

    return 0;
}

Comparison with standard new:

Feature	new	placement new
Memory Allocation	Performs allocation	Does not perform allocation
Constructor Call	Calls constructor	Calls constructor
Destructor Call	Called with delete	Must be called explicitly
Use Cases	General heap allocation	Memory pools, pre-allocation