When is the constructor called?

Question

In which of the following is the constructor of myClass called?

1.  myClass class1;
2.  myClass* class1;
3.  myClass* class1 = new myClass;

Thanks a lot

Answer 1

1. Yes - default constructor, instance created on stack
2. No
3. Yes - default constructor, instance created on heap

Answer 2

1. The statement would instatiate an object on the stack, call c'tor.
2. Defines only a pointer variable on the stack, no constructor is called.
3. The new operator would create an object in free store (usually the heap) and call c'tor.

But this code will not instantiate any object, as it does not compile. ;-) Try this one:

myClass class1; 
myClass* class2;
myClass* class3 = new myClass; 

• class 1 is a local variable (on the stack), constructor called.
• class 2 is a pointer, no constructor called.
• class 3 is a pointer, the constructor is called, when new is executed.