static member object linking error

Question

I am getting linking error when I build the project. I have a static member pointer which I am setting from a static member function. Any ideas what's the problem

class Logger
{

 private:   
  static MyComp* pComp;
 public:    
  static void setComp(MyComp* comp);
      // more methods ..
};  

void Logger::setComp(MyComp* comp)

{   
pComp = comp; 
}

Get the linking error

Undefined symbols for architecture x86_64:
"Logger::pComp", referenced from:
Logger::setComp(MyComp*) in Logger.o

score 4 · Accepted Answer · answered Sep 08 '13 at 20:20

4

You forgot to add

  MyComp* Logger::pComp;

to your cpp file (outside the class declation).

answered Sep 08 '13 at 20:20

Doc Brown

19,739
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that worked, thanks why is it needed anyway ? – Ahmed Sep 08 '13 at 20:25
@Ahmed Because `static void setComp(MyComp* comp);` is a declaration, not a definition. – Sep 08 '13 at 20:27

score 0 · Answer 2 · answered Sep 08 '13 at 20:53

0

In order to initialize a static data-member we must include a formal definition outside the class.

answered Sep 08 '13 at 20:53

elnineo

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static member object linking error

2 Answers2