Why can't static member methods access its non-static method in C++?

Question

I had to make a callback interface for a new module while I work, so I made a static method in a class.

One thing I still don't understand is why I can't call a non-static member method in a static member like this :

class CAdapterUser
{
public:
    CAdapterUser()          {}
    virtual ~CAdapterUser() {}

    void        Test();
    void        Test2();

protected:
    CAdapter    m_Adapter;

    unsigned char buffer[16];

    static void TestFunc(void* apContext);
};

void 
CAdapterUser::TestFunc( void* apContext )
{
//  CAdapterUser* pUser = (CAdapterUser*)apContext;
    CAdapterUser* pUser = reinterpret_cast<CAdapterUser*>(apContext);

    pUser->Test2();         // Compile error : LNK2019
    pUser->buffer[0] = 1;   // Even though I can access protected member variable?
}

Could someone answer my question?

Did you actually add a function definition for `Test2`? A link error suggest you did not. — NathanOliver, Mar 13 '19 at 13:14
@tntxtnt OP is using `pUser->Test2();` not `this->Test2();`. It should be fine. — François Andrieux, Mar 13 '19 at 13:15
https://learn.microsoft.com/en-us/cpp/error-messages/tool-errors/linker-tools-error-lnk2019 Maybe OP haven't defined `Test2()` yet. — tnt, Mar 13 '19 at 13:17
@tntxtnt - Clearly they haven't defined `Test2`. But what do static data members have to do with it? — StoryTeller - Unslander Monica, Mar 13 '19 at 13:18
Sorry it's just something I copied from google should have posted the link. Update it now — tnt, Mar 13 '19 at 13:21
@tntxtnt Whenever you copy somebody else's words/work, you should use "quotation formatting" to indicate that it is not your words/work. Or when the words don't apply to the topic at all, maybe just don't copy them at all ;) — Lightness Races in Orbit, Mar 13 '19 at 13:26

score 1 · Answer 1 · answered Mar 13 '19 at 13:15

1

LNK2019 is unresolved symbol, probably you simply forgot to implement Test2().

answered Mar 13 '19 at 13:15

Matteo Italia

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Oh, my mistake..thank you for your advice. – Sungsu Kim Mar 13 '19 at 13:17

Why can't static member methods access its non-static method in C++?

1 Answers1