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grumpy · Oct 30th, 2006, 3:12 AM

The reason for your error is that a forward declaration of a class is insufficient to allow declaration of an instance. So;

(Toggle Plain Text)

class Point;

class Rectangle
{
    // other stuff
    Point upLeft;
};

will fail. The way to eliminate it is to ensure that the complete declaration of class Point is seen by the compiler before it reaches the declaration of class Rectangle.

Partially related to your problem is that Point.h #include's Rectangle.h which #include's Point.h ..... That will not loop forever because you have employed #include guards, but is an issue because you will get different behaviour for other source files, depending on whether they #include Point.h or Rectangle.h first.

Oct 30th, 2006, 3:12 AM	#26
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,206 Rep Power: 5	The reason for your error is that a forward declaration of a class is insufficient to allow declaration of an instance. So; (Toggle Plain Text) class Point; class Rectangle { // other stuff Point upLeft; }; class Point; class Rectangle { // other stuff Point upLeft; }; will fail. The way to eliminate it is to ensure that the complete declaration of class Point is seen by the compiler before it reaches the declaration of class Rectangle. Partially related to your problem is that Point.h #include's Rectangle.h which #include's Point.h ..... That will not loop forever because you have employed #include guards, but is an issue because you will get different behaviour for other source files, depending on whether they #include Point.h or Rectangle.h first.