Win32 C/C++ Only one instance of an application is allowed to run, http://johnmhsheep.pixnet.net/blog, https://johnmhsieh.blogspot.com/

SingleInstance.cpp

#include "SingleInstance.h"
//
CSingleInstance::CSingleInstance(TCHAR* pMutexName)
{
	this->m_hMutex = CreateMutex(NULL, FALSE, pMutexName);
	this->m_bExist = (ERROR_ALREADY_EXISTS == GetLastError())?TRUE:FALSE;
}
CSingleInstance::CSingleInstance(const CSingleInstance& instance)
{
	if (this == &instance)
	{
		return;
	}
	//
	// Do nothing
	//
}
CSingleInstance& CSingleInstance::operator=(const CSingleInstance& instance)
{
	//
	// Do nothing
	//
	return *this;
}
CSingleInstance::~CSingleInstance()
{
	if (this->m_hMutex != NULL)
	{
		CloseHandle(this->m_hMutex);
		this->m_hMutex = NULL;
	}
}
BOOL CSingleInstance::IsRunning(void)
{
	return this->m_bExist;
}

SingleInstance.h

#ifndef _SingleInstance_H_
#define _SingleInstance_H_
//
#include <Windows.h>
//
// Only one instance of an App is allowed to run.
// Usage: declare a global object, it doesn't work to declare a local.
// CSingleInstance si(L"MySingleInstance");
//
class CSingleInstance
{
public:
	CSingleInstance(__in_opt TCHAR* pMutexName);
	CSingleInstance(__in const CSingleInstance& instance);
	CSingleInstance& operator=(__in const CSingleInstance& instance);
	~CSingleInstance();
	BOOL IsRunning(void);
private:
	HANDLE m_hMutex;
	BOOL m_bExist;
};
//
#endif