Question

I have several identical string constants in my program:

const char* Ok()
{
  return "Ok";  
}

int main()
{
  const char* ok = "Ok";
}

Is there guarantee that they are have the same address, i.e. could I write the following code? I heard that GNU C++ optimize strings so they have the same address, could I use that feature in my programs?

int main()
{
  const char* ok = "Ok";
  if ( ok == Ok() ) // is it ok?
  ;
}

Answer 1

There’s certainly no guarantee, but it is a common (I think) optimization.

The C++ standard says (2.13.4/2 “String literals):

Whether all string literals are distinct (that is, are stored in nonoverlapping objects) is implementation-defined.

To be clear, you shouldn’t write code that assumes this optimization will take place – as Chris Lutz says, C++ code that relies on this is code that’s waiting to be broken.