Circular C++ Header Includes

c++ static include circular-dependency
paul simmons picture paul simmons · Aug 15, 2009 · Viewed 8.7k times · Source

In a project I have 2 classes:

// mainw.h

#include "IFr.h"
...
class mainw
{
public:
static IFr ifr;
static CSize=100;
...
};

// IFr.h

#include "mainw.h"
...
class IFr
{
public float[mainw::CSize];
};

But I cannot compile this code, getting an error at the static IFr ifr; line. Is this kind of cross-inclusion prohibited?

Answer

ChrisW picture ChrisW · Aug 15, 2009

Is this kind of cross-inclusions are prohibited?

Yes.

A work-around would be to say that the ifr member of mainw is a reference or a pointer, so that a forward-declaration will do instead of including the full declaration, like:

//#include "IFr.h" //not this
class IFr; //this instead
...
class mainw
{
public:
static IFr* ifr; //pointer; don't forget to initialize this in mainw.cpp!
static CSize=100;
...
}

Alternatively, define the CSize value in a separate header file (so that Ifr.h can include this other header file instead of including mainw.h).

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