Unknown override specifier + missing type specifier - c++

Question

I'm using Visual Studio 2015 Update 2.
I have two headers called Error.h and Game.h.
Error.h:
#ifndef _Error_H
#define _Error_H
#include "Main.h"
#include "Core.h"
#include <Log.h>
#include <CWindows.h>
// ErrorIDs
enum
{
ErrUnknownID = 0,
blah,
blah2,
blah3
};
struct ErrInfo
{
unsigned int eiID;
String strCaption; // String is another class which implemented from std::string which works fine!
String strText;
bool bFixable = false;
};
// Static errors
extern ErrInfo WinNotSupported;
// blah blah
class Error
{
public:
void Initialize();
bool ShowError(ErrInfo ErrorInfo);
BOOL FixError(unsigned int uiErrorID);
// -----------------------------------------
// --------------- Singleton ---------------
// -----------------------------------------
public:
static Error& Instance()
{
static Error instance;
return instance;
}
static Error *InstancePtr()
{
return &Instance();
}
private:
Error()
{
}
public:
Error(Error const&) = delete;
void operator=(Error const&) = delete;
};
#endif // !_Error_H
And Game.h:
#ifndef _Game_H
#define _Game_H
#include "Main.h"
#include "Error.h"
#include "Core.h"
#include <CWindows.h>
#include <AFile.h>
struct missingfileSt
{
String strFileURL;
String strDLFileName;
String strFileName;
String strChecksum;
long long llSize;
ErrInfo errError; // Many errors here <-
};
struct deletablefileSt
{
String strFileName;
ErrInfo errError; // Many errors here too
};
#define siMissingFiles 7
#define siDeletableFiles 5
class Game
{
public:
void ValidateFiles();
DWORD dwGamePID;
missingfileSt mfMissingFiles[siMissingFiles];
deletablefileSt dfDeletableFiles[siDeletableFiles];
// -----------------------------------------
// --------------- Singleton ---------------
// -----------------------------------------
public:
static Game& Instance()
{
static Game instance;
return instance;
}
static Game *InstancePtr()
{
return &Instance();
}
private:
Game()
{
dwGamePID = 0;
}
public:
Game(Game const&) = delete;
void operator=(Game const&) = delete;
};
#endif // !_Game_H
Now, when I compile I get many errors from Game.h and all of them are:
Error C3646 'errError': unknown override specifier
Error C4430 missing type specifier - int assumed. Note: C++ does not support default-int
I got really confused, why errors!?
Also I must say, in header Core.h it will include Error.h again but it mustn't be problem!

Answer 1

An old question already but a useful answer is missing for all C++ newbies or those who are forced to understand (very) bad C++ compiler messages.
If you get "missing type specifier", "unknown override", "undefined type/class", "syntax error: (" (for a beginning function parameter list) although you included the proper header file then it indicates that there is some circular reference in your include-hierarchy. This is also true if you have a forward declaration and the type is still "unknown".
The only solution with the old include-system in C++ is to avoid circular references between #includes. It's achieved by moving #includes from a header file A.h to the A.cpp and by forward declaring the types (or methods) in A.h. If you don't move the #include to A.cpp it still can fail despite forward declaration.
Let A.h be a circular include in B.h because B.h would already be included by A.h. Instead of
#include "A.h"
class B {
A a;
}
you can write
class A;
class B {
A a;
}
and include A.h in your CPP file(s).
You can avoid the need for method forward declarations if you only define methods in CPP files.

Answer 2

I just moved ErrInfo struct to another header with the same include guard and it compiled and worked without problem, I think it's compiler failure, if it isn't please explain.