Re: Singleton class fails on reboot

From:
"Doug" <DugzDC@blueyonder.co.uk>
Newsgroups:
comp.lang.c++,comp.os.ms-windows.programmer.win32
Date:
9 Jul 2006 14:36:28 -0700
Message-ID:
<1152480988.728864.261360@b28g2000cwb.googlegroups.com>
keepyourstupidspam@yahoo.co.uk wrote:

mlimber wrote:

mlimber wrote:

See chapter 6 of _Modern C++ Design_ for more than you ever wanted to
know about templates in C++.


             ^^^^^^^^^

I meant "singletons" not "templates" (although, the latter might also
apply). --M


Thanks, I will try it out.

But this is the singleton template I was using, do you see any issues
why this would not start when the machine reboots.

class DLLEXPORT CSingleton
{
public:

    // Return A reference to the instance of the CSingleton class.
    // If there is no instance of the class yet, one will be created.
    static T& Instance()
    {
        if (m_instance == 0 )
        {
            if (m_instance == 0)
            {
                m_instance = new T;

                // exit processing function
                std::atexit(CSingleton::DestroyInstance);
            }
        }
        return *(CSingleton::m_instance);
    };

    // Destroys the CSingleton class instance.
    // Be aware that all references to the single class instance will be
    // invalid after this method has been executed!
    static void DestroyInstance()
    {
        delete m_instance;
        m_instance = NULL;
    };

protected:

    // shield the constructor and destructor to prevent outside sources
    // from creating or destroying a CCSingleton instance.

    inline explicit CSingleton() { CSingleton::m_instance =
static_cast<T*>(this); }
    inline ~CSingleton() { CSingleton::m_instance = 0; }

private:

    inline explicit CSingleton(CSingleton const&) {}
    inline CSingleton& operator=(CSingleton const&) { return *this; }

private:

    static T* m_instance; // CSingleton class instance
};

// static class member initialisation.
//template <typename T> T* CSingleton<T>::m_instance = 0;

~Enda


Hiya,

Other than the odd double-if test around mInstance (which won't help
with locking, if that's what it's for), I can't see any reason why this
would give you any problems.

Doug

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