std::aligned_union

// aligned_union example
#include <iostream>
#include <type_traits>

union U {
  int i;
  char c;
  double d;
  U(const char* str) : c(str[0]) {}
};       // non-POD

typedef std::aligned_union<sizeof(U),int,char,double>::type U_pod;

int main() {
  U_pod a,b;              // default-initialized (ok: type is POD)
  new (&a) U ("hello");   // call U's constructor in place
  b = a;                  // assignment (ok: type is POD)
  std::cout << reinterpret_cast<U&>(b).i << std::endl;

  return 0;
}