typedef across same namespace in different header files

Question

I'm currently learning c++ and struggling with some code:

Garden.h:

#ifndef GARDEN_H_
#define GARDEN_H_
#include <vector>
#include <boost/tr1/memory.hpp>
#include "Shape.h"
#include "Utils.h"
namespace cma {
 typedef boost::shared_ptr<cma::Shape> ShapePtr;
 typedef std::vector<cma::ShapePtr> GardenPlan;
}
#endif /* GARDEN_H_ */

Utils.h:

#ifndef UTILS_H_
#define UTILS_H_
#include "Garden.h"
namespace cma {
 void printList(GardenPlan const & p, std::ostream & o);
}
#endif /* UTILS_H_ */

The compiler output:

In file included from ../src/Garden.h,
 from ../src/Utils.cpp:
../src/Utils.h: error: variable or field 'printList' declared void
../src/Utils.h: error: 'GardenPlan' was not declared in this scope
../src/Utils.h: error: expected primary-expression before '&' token
../src/Utils.h: error: 'o' was not declared in this scope

I seriously just don't get it.

• Lstor: Note the typo in your Garden.h header guard.
• Kiril Kirov: You can remove the #include "Utils.h" from Garden.h as you don't need it and this causes some problems
• cimnine: The typo wasn't the source of the failure. And I don't want to remove Utils.h as I would like to only #include "Garden.h" in my main program. Is there a way around?
• quamrana: possible duplicate of Classes as parameters error
• Kiril Kirov: @cimnine - yes, there is: remove #include "Utils.h", create a new header, that includes Utils.h and Garden.h and then include the new header in your main program. Problem solved (:

Answer 1

You have a cyclical include problem.

You're including Garden.h in Utils.h and Utils.h in Garden.h.

You either need to put both definitions in the same header file or forward declare one of the types.

However, you don't actually need to include Utils.h in Garden.h so removing that include should solve your problem.