unresolved external symbol

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error LNK2001: unresolved external symbol "class CCdxUAttSpecs * m_pUAS" (?m_pUAS@@3PAVCCdxUAttSpecs@@A)

in cdxuatts.h, I have the following code:

C#

public:
    void FixSize(char *, int);

in cdxuattspecs.h, I have the following code:

C#

public:
	int		GetAndSetSpecs(int, char *);
	CString		m_szHelp;

in cdxuattqr.cpp I have the following code:

C#

#include "CdxUAtts.h"
#include "CdxUAttSpecs.h"

extern  CCdxUAttSpecs   *m_pUAS;    // <--- why unresolved???
extern  CCdxUAtts       *m_pUA;
.
.
.
   m_pUA->FixSize(name, 16);
.
.
.
   if(m_pUAS->GetAndSetSpecs(1, text))
      m_szUAQRHelp = m_pUAS->m_szHelp;
.
.
.

Can this be related to the fact that GetAndSetSpecs is an "int" while FixSize is "void"?

Prior to adding the code referencing CCdxUAttSpecs, the code that referenced CCdxUAtts compiled, linked and executed just fine. I fully expected the same to happen with CCdxUAttSpecs but for some reason, I get a link error.

Posted 24-Sep-12 7:16am

tom_delorenzo

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tom_delorenzo 24-Sep-12 13:47pm

Although it appeared as if neither were defined (and since one worked why shouldn't they both work), in actuality, m_pUA was defined in another routine. Thank you.

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CPallini · Accepted Answer · 2012-09-24T07:21:00

Solution 1

The reference to the variable m_pUAS is unresolved because you never defined it.
In one source code (that is .cpp)) you have to define m_pUAS, e.g.

C++

CCdxUAttSpecs   *m_pUAS = NULL;

Posted 24-Sep-12 7:21am

CPallini

Comments

Chuck O'Toole 24-Sep-12 13:46pm

In addition to CPallini's excellent response, you've "declared" m_pUAS to be external to your code. OK, but that doesn't "define" the instance of the variable. "extern" only declares an attribute of the variable not the instance of it.

Sergey Alexandrovich Kryukov 24-Sep-12 17:07pm

Exactly. Good point: this is even more essential bug than not declaring at all, as this is a big misconception. You got it right -- a 5. :-)
--SA

Sergey Alexandrovich Kryukov 24-Sep-12 17:05pm

Of course. Definitions in, garbage out... :-)
My 5,
--SA

CPallini 25-Sep-12 3:08am

Thank you.