统计程序实例的个数

/**********windows核心编程实例17-AppInst**********/
/***展示：应用程序如何知道在任一时刻有多少个自己的实例正在运行***/

#include <windows.h>
#include "resource.h"

int g_uMsgAppInstCountUpdate = WM_APP + 123;

#pragma data_seg("Shared")
volatile LONG g_lApplicationInstances = 0;
#pragma data_seg()

#pragma comment(linker, "/Section:Shared,RWS") // 引号内不能加空格

void DlgCommand(HWND hwnd, int id, HWND hwndCtl, UINT codeNotify)
{
	switch (id)
	{
	case IDCANCEL:
		EndDialog(hwnd, id);
		break;

	default:
		break;
	}
}

INT_PTR WINAPI DlgProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	if (uMsg == g_uMsgAppInstCountUpdate)
	{
		SetDlgItemInt(hwnd, IDC_COUNT, g_lApplicationInstances, FALSE);
	}

	switch (uMsg)
	{
	case WM_INITDIALOG:
		PostMessage(HWND_BROADCAST, g_uMsgAppInstCountUpdate, 0, 0);
		break;

	case WM_COMMAND:
		DlgCommand(hwnd, LOWORD(wParam), (HWND)lParam, uMsg);
		break;

	default:
		break;
	}

	return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE, PTSTR, int)
{
	g_uMsgAppInstCountUpdate = RegisterWindowMessage(TEXT("MsgAppInstCountUpdate"));
	
	InterlockedExchangeAdd(&g_lApplicationInstances , 1);
	
	DialogBox(hInstance, MAKEINTRESOURCE(IDD_DIALOG1), NULL, DlgProc);

	InterlockedExchangeAdd(&g_lApplicationInstances, -1);

	PostMessage(HWND_BROADCAST, g_uMsgAppInstCountUpdate, 0, 0);

	return 0;
}