invalid use of incomplete type

Js::Number extends Js::JVar extends Var
Js::JVar uses Js::Number in it.

So I've included jvar.h in Js::Number class. which compiles fine.
and I've made forward reference for Js::Number in jvar.h which doesn't compile and fires compilation errors.

Code:

jvar.cpp:31: error: invalid use of incomplete type 'struct Js::Number'
jvar.h:31: error: forward declaration of 'struct Js::Number'

and here goes my source code

jnumber.h

Code:

#include <../var.h>
#include "jvar.h"

namespace Js {
class Number : public Js::JVar{
  private:
    Var num;
  public:
    Number();
    Number(unsigned int val);
    Number(unsigned long val);
    Number(unsigned short val);
    Number(double val);
    Number(float val);
    Number(int val);
    Number(short val);
    Number(long val);
    ~Number();
};

}

Js::Number Compiles fine.

jvar.h

Code:

#include <string>
#include <memory>
#include "../var.h"

using std::string;
using std::auto_ptr;

namespace Js{
  class Number;//Line 31
  class String;
  class Array;
  class Object;
  class Function;
  class Bool;
}

namespace Js {
class JVar: public Var{
  private:
    string lhs;
    Var* rhs;
  public:
    JVar();
    JVar(JVar*);
    JVar(long);
    .....
}

jvar.cpp

Code:

.....
Js::JVar::JVar(long r): Var(), rhs(0x0){
	Js::Number* x = new Js::Number(r);//Line 31
	//rhs = auto_ptr<Var>(dynamic_cast<Var*>(x));
}
.....

It's hard to say, but jvar.cpp has to see jnumber.h when you create an instance of Js::Number. So you'll have to put a

Code:

#include "jnumber.h"

somewhere

Just because your program can see that Js::Number is a name, doesn't mean it can see the constructor for it. Why can't you include jnumber.h (maybe instead of jvar.h, if you don't have inclusion guards) so that it can see the class definition?

Did you define Js::Var?

It works when I include jnumber.h in jvar.cpp
But it doesn't if I include jnumber.h in jvar.h instead of jvar.cpp
Why ??
as jvar.h is included by jvar.cpp all the files that jvar.h includes should be included in a chain (In Theory !!) right ?

I remember this exact question coming up a week or two ago. I remember it being answered, at that.

Is that in my thread ??

Originally Posted by noobcpp

It works when I include jnumber.h in jvar.cpp
But it doesn't if I include jnumber.h in jvar.h instead of jvar.cpp
Why ??
as jvar.h is included by jvar.cpp all the files that jvar.h includes should be included in a chain (In Theory !!) right ?

jvar.h includes jnumber.h...
jnumber.h includes jvar.h...
jvar.h includes jnumber.h...
jnumber.h includes jvar.h...
As you can probably figure out, this does not work quite well and explains also why it works if you put it inside your .cpp file.

Thanks
So #include is in .cpp so that it doesn't go into .hinclude Cycle