LNK 2019: Unresolved External Symbol

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// mainfrm.h
enum
{		
    logAll = 0xff
};
void Log(int nIdx, LPCTSTR lpText, int nType = logAll, LPCTSTR lpDeviceName = NULL);
//SesLog.h
int m_nDeviceID;
CString m_strDeviceName;
// SesLog.cpp
#include "Mainfrm.h"
#include "SesLog.h"
void CSessionLog::Log(LPCSTR lpText)
{
	if(m_pParent)
		m_pParent->Log(m_nDeviceID, lpText, logAll, m_strDeviceName);

error LNK2019: unresolved external symbol "public: void __thiscall CMainFrame::Log(int,char const *,int,char const *)" (?Log@CMainFrame@@QAEXHPBDH0@Z) referenced in function "public: void __thiscall CSessionLog::Log(char const *)" (?Log@CSessionLog@@QAEXPBD@Z) \SesLog.obj

VS 2010
Help would be appreciated.

Thanks

Posted 13-May-11 4:55am

Member 4581741

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2 solutions

Solution 3

Maybe you don't include the corresponding header file.

Posted 15-May-11 22:48pm

flyicing

Comments

CPallini 16-May-11 5:07am

Nope: that's a linker error, not a compiler one.

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Olivier Levrey · Accepted Answer · 2011-05-13T05:27:00

Solution 2

The linker couldn't find the Log function declared in class CMainFrame.

You did this declaration in MainFrm.h:

C++

void Log(int arg1, char const * arg2, int arg3, char const * arg4);

But you didn't write the implementation for this function anywhere. Check your MainFrm.cpp file and make sure you didn't forget or maybe commented it:

C++

//this function implementation doesn't exist.
//did you comment it?
void CMainFrame::Log(int arg1, char const * arg2, int arg3, char const * arg4)
{
    ....
}

By the way, I suppose you want to declare you char pointers parameters as const char* and not char const*...

Posted 13-May-11 5:27am

Olivier Levrey

v2

Comments

Albert Holguin 13-May-11 11:30am

I guess if it was a lib you wouldn't have a function declaration in your own code, my 5... :)

Olivier Levrey 13-May-11 11:46am

Thank you Albert. It is often tricky to solve linker issues, especially for beginners. I think OP will have some more problems: have a look to his last comment.

Albert Holguin 13-May-11 11:35am

Just noticed he has this m_pParent->Log but the Log prototype doesn't look like part of a class (at least he didn't show it as included in a class)

Member 4581741 13-May-11 11:39am

Ok i figured out that the header file MainFrm.h is coming from ..\rhub\mainfrm.h.
& in that rhub directory too it has Mainfrm.cpp which has Log function.

Now what do i need to do to call the function from that .cpp?
Should i add that cpp in my project ?

Advice
Thanks

Olivier Levrey 13-May-11 11:43am

Yes, you need the .cpp file. But it sounds strange. Do you mean you are using MainFrm.cpp from another project?? In that case, I predict a lot of errors coming...

Sergey Alexandrovich Kryukov 13-May-11 18:33pm

Agreed, a 5.
--SA

Niklas L 16-May-11 7:34am

Fived.