I have a complete error free program output is 3 but problem is that how did output come 3 can you please tell me. ?

Question

#include <iostream>
using namespace std;
class A {
public:
static int a;
A() {a++;}
};
int A::a=1;
void f(void){
A a;
throw string("?");

}
int main() {
A a;
try {f();}
catch (string &s){}
cout<<A::a;
return 0;
}

Answer 1

#include <iostream>
using namespace std;

class A {
public:
static int a;
A() {a++;}
};

int A::a=1;
// a initialized to 1.

void f(void){
A a;
throw string("?");

}
int main() {
A a;
// constructor of A is called.
// Value of a is now 2.
try {f();}
// constructor of A is called again.
// Value of a is now 3.
catch (string &s){}
cout<<A::a;
// prints 3.

return 0;
}

Answer 2

The second constructor is called in f, when you stated 'A a;'

Answer 3

@hatsy rei thanks
but can you please tell me why did constructor call two times ? it is confusing me

Answer 4

john well thanks