2011.01.13 - most vexing parse

among many pitfalls in C++ there is so called “most vexing parse”. as the name suggests, it is vexing. especially that it is a heritage from C.

consider given code:

#include <iostream>
struct S 
{
  S(){ std::cout<<"S()\n"; }
  S(const S&){ std::cout<<"S(cpctor)\n"; }
};
 
int main(void)
{
  S s( S() );
  return 0;
}

what will show on the screen? if your answer wasn't “nothing”, that read on on explanation on the most vexing parse¹⁾…