linker error, undefined reference?

[liyarax]

I'm getting some strange linker errors in my C++ project:

obj\Debug\main.o||In function `_ZSt19__iterator_categoryIPSsENSt15iterator_traitsIT_E17iterator_categoryERKS2_':|
)]+0xbf)||undefined reference to `Command::PVT'|
)]+0x17)||undefined reference to `Command::PVT'|
||=== Build finished: 2 errors, 0 warnings ===| 

Full class:

#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <cstdarg>
#include <vector>
#include <string>

class Command {
    public:
    Command() {}
    Command(std::string Eval) : IF(0) {
        Com.push_back("test");// 0
        for (unsigned int i = 0; Eval != Com.at(i); ++i) {
            if (i < Com.size()) {
                ++IF;
            } else {
                break;
            }
        }
        p_start(IF);
    }
    static void test() { std::cout << "test" << std::endl; }
    void Init() {
        PVT.push_back(test);//   0
    }
    void p_start(int F) {
        Init();
        (*PVT[F])();
    }
    ~Command() {}
    private:
    int IF;
    typedef void(*P2_F)(void);
    static std::vector<P2_F> PVT;
    std::vector<std::string> Com;
};

this has been baffling me for over an hour, it just doesn't make any sense at all. Anybody know whats up?

Edit: by the way, I'm using Code::Blocks compiler on windows 7

[sohguanh]

undefined reference to `Command::PVT'

In your class you have below statement.

static std::vector<P2_F> PVT;

You need to define it in your .cpp file. E.g

std::vector<P2_F> Command::PVT;