Is using NULL references OK?

Question

I came across this code:

void f(const std::string &s);

And then a call:

f( *((std::string*)NULL) );

A

Answer 1

f( *((std::string*)NULL) );

This is essentially dereferencing NULL, which on most systems is #defined to be 0. Last I checked 0x00000000 is an invalid memory address for doing anything.

Whatever happened to just checking

if (std::string.length() > 0) ....