Does a const reference class member prolong the life of a temporary?

Question

Why does this:

#include 
#include 
using namespace std;

class Sandbox
{
public:
    Sandbox(const string& n) : member(n) {         


        

Answer 1

Technically speaking, this program isn't required to actually output anything to standard output (which is a buffered stream to begin with).

• The cout << "The answer is: " bit will emit "The answer is: " into the buffer of stdout.

• Then the << sandbox.member bit will supply the dangling reference into operator << (ostream &, const std::string &), which invokes undefined behavior.

Because of this, nothing is guaranteed to happen. The program may work seemingly fine or may crash without even flushing stdout -- meaning the text "The answer is: " would not get to appear on your screen.