shared pointer null dereference text

shrd_ptr.cc

#include <iostream>
#include <memory>

int
main(int argc, char **argv)
{
  std::shared_ptr<int> ptr;

  try {
    std::cout << *ptr << std::endl;

  } catch (...) {
    std::cout << "Exception!" << std::endl;
  }
  return 0;
}

//% clang -Wall -std=c++11 -stdlib=libc++ -lc++ -o shrd_ptr shrd_ptr.cc
// --> zsh: segmentation fault  ./shrd_ptr

//% gcc -Wall -std=c++11 -lstdc++ -o shrd_ptr_gcc shrd_ptr.cc
// zsh: segmentation fault  ./shrd_ptr_gcc