CODEWITHSUNDEEP
c++
sazr
sazr

Reputation: 25928

Calling Static Member Function causes runtime error

I am getting a runtime access violation error when defining a static class variable. I'm not quite sure what is exactly going wrong; is the static function I am calling not implemented at the time of calling, something else?

What is going wrong and how can I fix this?

Runtime error (see code below for the line that the error occurs on):

0xC0000005: Access violation reading location 0x00000000.

Code:

// Status.h
class Status
{
public:
    // Static Properties//
    static const Status CS_SUCCESS;

    // Static Functions //
    static const Status registerState(const tstring &stateMsg)
    {
        int nextStateTmp = nextState + 1;
        auto res = states.emplace(std::make_pair(nextStateTmp, stateMsg));

        return (res.second) ? Status(++nextState) : Status(res.first->first);
    }

private:
    static std::unordered_map<STATE, tstring> states;
    static STATE nextState;
};


// Status.cpp
#include "stdafx.h"
#include "Status.h"

// Class Property Implementation //
State Status::nextState = 50000;
std::unordered_map<STATE, tstring> Status::states;
const Status S_SUCCESS = Status::registerState(_T("Success"));


// IApp.h
class IApp : protected Component
{
public:

    static const Status S_APP_EXIT;
    static const Status S_UNREGISTERED_EVT;

    ...
};


// IApp.cpp
#include "stdafx.h"
#include "../EventDelegate.h"
#include "../Component.h"
#include "IApp.h"

// Class Property Implementation //
const Status IApp::S_APP_EXIT = CStatus::registerState(_T("IApp exit")); // Runtime error: 0xC0000005: Access violation reading location 0x00000000.
const Status IApp::S_UNREGISTERED_EVT = CStatus::registerState(_T("No components registered for this event"));

Upvotes: 2

Views: 603

Answers (1)

Marco A.
Marco A.

Reputation: 43662

Some static variables like S_APP_EXIT depend on other static variables (e.g. nextState) for their initialization.

Read about the static initialization order fiasco and fix your code accordingly (making nextState a private variable?). You might even think of using the Construct On First Use Idiom (explained in the other FAQ here).

Anyway I wouldn't generally advise keeping all those variables static, but it's quite hard to tell from just the excerpt you posted (where is CS_SUCCESS defined?).

Upvotes: 1

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