Why is stack unwinding not happening (demo)?

I was hoping to see “exiting” printed, but I’m not getting that,
stack unwinding isn’t happening.

#include<iostream>
#include<cstdio>
using namespace std;

class mytemp
{
    std::string theA;
    public:
      mytemp(const std::string& a)
      {
        theA = a;
        printf("n entering %sn", theA.c_str());
      }
      ~mytemp()
      {
        printf("n exiting %sn", theA.c_str());
        fflush(NULL);
      }
};

void C(int x )
{
  mytemp obj("==c==");
  throw 1;
  //cout<<1/0;
}

void B(int y )
{
  mytemp obj("==b==");
  C(30);
}

void A(int z)
{
  mytemp obj("==a==");
  B(20);
}

int main()
{
  A(10);
  return 0;
}