Multiple Syntax Errors When Referencing Another Class in Include File [duplicate] - c++

Question

This question already has answers here:
Resolve build errors due to circular dependency amongst classes
(12 answers)
Closed 2 years ago.
Have two files:
CIoHandler.h
#pragma once
#include "CSession.h"
class CIoHandler
{
public:
CIoHandler();
~CIoHandler();
void AuthenticateUser();
void ConvertUnicodeToAscii();
void DoNTLMAuth();
void GetAndSetSocket();
void GetElevatedToken();
void GetHeaderMessage();
void GetUserNameW();
void HandleOperatorMessage();
void Init(CSession *cSession);
void IsLocalAccount();
int IsLoopBack();
void IsSPNFQDNName();
int IsSPNLocalInterface();
void IsSPNPresentInRegistry();
void IsTimedOut();
void IssueReadFromSocket();
void OnDataFromSocket();
void OnReadFromPipeCompletion();
void ParseAndValidateAccount();
void ProcessAuthenticationLine();
void ProcessCommandLine();
void ProcessDataFromSocket();
void ReadRegistryKey();
void SendDetailsAndAskForLicense();
void SendMessageToClient();
void SendTerminateString();
void SetPrivilege();
void WriteMessageToClientDirectly();
void WriteToClient();
void WriteToServer();
void WriteToSocket();
};
CSession.h
#pragma once
#include "CIoHandler.h"
class CSession
{
private:
CIoHandler* _CIoHandler;
public:
CSession();
~CSession();
void CollectPeerInfo();
void FreeInitialVariables();
void GetRegistryValues();
void Init();
void IsAnAdministratorOrMember();
void SecpSetIPandPort();
void Shutdown();
void WaitForIO();
};
When compiling with Visual Studio 2019 get the following errors:
CSession.h(8,13): error C2143: syntax error: missing ';' before '*'
CSession.h(8,13): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
CSession.h(8,26): error C2238: unexpected token(s) preceding ';'
CIoHandler.h(16,22): error C2061: syntax error: identifier 'CSession'
CIoHandler.h(16,22): error C2061: syntax error: identifier 'CSession'
Removing
#include "CIoHandler.h"
private:
CIoHandler* _CIoHandler;
From CSession.h it compiles
What do I need to so I can use CIoHandler in CSession class definition

Answer 1

You have a cyclic include dependency. To break the cycle replace
#include "CIoHandler.h"
with a forward declaration.
class CIoHandler;