Why can I not call my class's constructor from an instance of that class in C++?

Question

When can an object of a class call the destructor of that class, as if it\'s a regular function? Why can\'t it call the constructor of the same class, as one of its regular

Answer 1

I think you can explicitly call the destructor if you make sure that the instance is replaced/recreated with a call to placement new:

class c
{
public:
   void add() ;
   c();
   ~c() ;
};

int main()
{
 c objC  ;
 objC.add() ;
 objC.~c() ; // this line compiles
 new (&objC) c;  // placement new invokes constructor for the given memory region
}

I've never seen this in practice, but logically it should work (unless c's constructor can throw, in which case, I imagine, hell could break loose during stack unwinding).

However, what you probably want is just assignment:

objC = c();

If the destructor has side-effects that you are interested in, implement assignment using the copy-and-swap idiom which gets the destructor invoked for the "left-hand" value.