Question

For example,

   class Segment
   {
      friend bool someFunc( P_Segment p );
   };

typedef boost::shared_ptr<Segment> P_Segment;

How best to declare P_Segment so this compiles?

Answer 1

In this case you have no choice since you can’t forward declare typedefs. You’ll have to forward declared the Segment class instead.

class Segment;

typedef boost::shared_ptr<Segment> P_Segment;

class Segment
{
    friend bool someFunc( P_Segment p );
};