If 'Test' is an ordinary class, is there any difference between: Test* test = new Test; and Test* test = new Test();

In C++, the syntax Test* test = new Test; and Test* test = new Test(); are both used to create objects dynamically on the heap using pointers. However, there is a difference in terms of object initialization.

    Test* test = new Test;: This syntax creates an object of the Test class without explicitly invoking its constructor. The object is allocated on the heap, but the constructor of the Test class is not called. This can lead to uninitialized members if the class has members that require initialization.

    Test* test = new Test();: This syntax creates an object of the Test class and explicitly invokes its default constructor. The object is allocated on the heap, and the constructor of the Test class is called. This ensures that the object's members are properly initialized.

Here's a simple example to illustrate the difference:

cpp

#include <iostream>

class Test {
public:
    Test() {
        std::cout << "Constructor called" << std::endl;
    }
};

int main() {
    Test* test1 = new Test;    // Constructor not explicitly called
    Test* test2 = new Test();  // Constructor explicitly called
    
    delete test1;
    delete test2;
    
    return 0;
}

In this example, you'll see that the constructor is only called for the object created using new Test(). The object created using new Test is created without calling the constructor, and if you try to access its members, you might encounter undefined behavior due to uninitialized data.

In modern C++, it's generally recommended to avoid using raw pointers and instead use smart pointers or stack-based objects to manage memory and object lifetime. Using stack-based objects or smart pointers ensures that constructors and destructors are properly called, reducing the risk of resource leaks and undefined behavior.