Can't increment a static variable

Question

Could you help me understand why I can't increment the static variable? I face this: *error LNK2001: unresolved external symbol "private: static unsigned int Counter::m_curCounters" (?m_curCounters@Counter@@0IA)*

counter.cpp

#include "counter.h"

static unsigned int m_curCounters = 0;

Counter::Counter(const char* p){
    ...
    m_curCounters++;
}


Counter::Counter(){
    ...
    m_curCounters++;
}

Answer 1

I think whats happening here that you have m_curCounters declared in counter.h and that you create a new local static in the cpp. But class statics need to be visible to the linker by defining them in the cpp as unsigned int Counter::m_curCounters = 0;

Now when you try to use the local static the compiler gives precedence to the class static which the linker cant find later on

Answer 2

I suppose you have m_curCounters declared in Counter.
Then you need to define it as

unsigned int Counter::m_curCounters = 0;