cannot access private member error when porting MFC project

On the forum, we have surfaced another error. I had a chance today to see a real-world code with this error and actually to narrow down the problem. So if you see an error like

1>c:\program files\microsoft visual studio 8\vc\atlmfc\include\afxwin.h(259) : error C2248: 'CObject::operator =' : cannot access private member declared in class 'CObject'

1> c:\program files\microsoft visual studio 8\vc\atlmfc\include\afx.h(540) : see declaration of 'CObject::operator ='

1> c:\program files\microsoft visual studio 8\vc\atlmfc\include\afx.h(510) : see declaration of 'CObject'

1> This diagnostic occurred in the compiler generated function 'CGdiObject &CGdiObject::operator =(const CGdiObject &)'

The cause of this error is that you are have a class like

class CReproClass {

public:

CReproClass::CReproClass(void) {}

CReproClass::~CReproClass(void) {}

CPen m_pen; //or any other class that subclasses CGdiObject

};

or

class CReproClass : public CPen{

...
};

then is later used in 

CReproClass a;
CReproClass b;
a = b;

This is the cause of the problem.

Comments

• Anonymous
  March 26, 2007
  Thanks for the help, this saved me hours!

• Anonymous
  May 19, 2008
  The comment has been removed

• Anonymous
  August 05, 2008
  Hey dude, thank you so much for this!!!  I've been looking everywhere for a simple, yet comprehensive explanation for this compilation error, and nothing can be found.   This really hits the spot.  Thank you so much for this!!

• Anonymous
  October 22, 2008
  Here is my problem similar ti this. i have written a code to update my combo box content to my local structure.Something like following.At this point the error is comming. void CMeterpollingConfiguration::getMeterPoolingConfigData() { #if 1    COleDateTime DateTime;    sprintf(g_stMeterpollingconf.cDateTimeBC,"%04d-%02d-%02d %02d:%02d:%02d", DateTime.GetYear(), DateTime.GetMonth(), DateTime.GetDay(), DateTime.GetHour(), DateTime.GetMinute(), DateTime.GetSecond()); #endif    if(m_MeterpollingBillingData == TRUE)    {        g_stMPCTypeofdata.cbMPCBMinute = m_MpcBdMinutes;        g_stMPCTypeofdata.csMPCBSubminutes = m_MpcBdMinute;        g_stMPCTypeofdata.cbMPCBHours = m_MpcBdHours;        g_stMPCTypeofdata.cbMPCBDay = m_MpcBdDay;        g_stMPCTypeofdata.cbMPCBDate = m_MpcBdDate;    }    else if(m_MpcLoadServyData == TRUE)    {          g_stMPCTypeofdata.cbMPCBMinute = m_MpcLsdMinutes;        g_stMPCTypeofdata.csMPCBSubminutes = m_MpcLsdMinute;//m_MpcLsdMinute        g_stMPCTypeofdata.cbMPCBHours = m_MpcLsdHours;        g_stMPCTypeofdata.cbMPCBDay = m_MpcLsdDay;        g_stMPCTypeofdata.cbMPCBDate = m_MpcLsdDate;    }    else if(m_MPCFullData == TRUE)    {          g_stMPCTypeofdata.cbMPCBMinute = m_MpcFdMinutes;        g_stMPCTypeofdata.csMPCBSubminutes = m_MpcFdminute;//m_MpcLsdMinute        g_stMPCTypeofdata.cbMPCBHours = m_MpcFdHours;        g_stMPCTypeofdata.cbMPCBDay = m_MpcFdDay;        g_stMPCTypeofdata.cbMPCBDate = m_MpcFdDate;    }    else if(m_MpcTamperData == TRUE)    {          g_stMPCTypeofdata.cbMPCBMinute = m_MpcTdMinutes;        g_stMPCTypeofdata.csMPCBSubminutes = m_MpcTdMinute;//m_MpcLsdMinute        g_stMPCTypeofdata.cbMPCBHours = m_MpcTdHours;        g_stMPCTypeofdata.cbMPCBDay = m_MpcTdDay;        g_stMPCTypeofdata.cbMPCBDate = m_MpcTdDate;    }    else if(m_MpcInstData == TRUE)    {          g_stMPCTypeofdata.cbMPCBMinute = m_MpcIdMinutes;        g_stMPCTypeofdata.csMPCBSubminutes = m_MpcIdMinute;//m_MpcLsdMinute        g_stMPCTypeofdata.cbMPCBHours = m_MpcIdHours;        g_stMPCTypeofdata.cbMPCBDay = m_MpcIdDay;        g_stMPCTypeofdata.cbMPCBDate = m_MpcIdDate;    }    else    {} return; } here pls note that :i'm updating different combo box content to same structure variables,by using if...else if ..else statement. while compilation i 'm getting error " 'CObject::operator =' : cannot access private member declared in class 'CObject'" which is in compiler genetated file(afxwin.h). Pls help me to slove this problem. Thanks.

• Anonymous
  March 08, 2009
  The comment has been removed