请问为什么在WM_QUERYENDSESSION或者WM_ENDSESSION中发出WM_QUIT，消息循环无法终止？

[沙老师]

请问为什么在WM_QUERYENDSESSION或者WM_ENDSESSION中发出WM_QUIT，消息循环无法终止？

#include <windows.h>
#include "EvntLog.h"
#include "Program.h"

// 类名
TCHAR szClassName[] = TEXT("ClassName");
// 标题
TCHAR szWindowName[] = TEXT("WindowName");

CEvntLog *pEvntLog;
CProgram *pProgram;

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int APIENTRY WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
MSG msg;
HWND hWnd;
WNDCLASS wc;

pEvntLog = new CEvntLog;
pProgram = new CProgram(pEvntLog);

// 注册窗口类
wc.style = CS_VREDRAW | CS_HREDRAW;
wc.lpfnWndProc = (WNDPROC)WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon( NULL, IDI_APPLICATION );
wc.hCursor = LoadCursor( NULL, IDC_ARROW );
wc.hbrBackground = (HBRUSH)(COLOR_BTNFACE + 1);
wc.lpszMenuName = NULL;
wc.lpszClassName = szClassName;
RegisterClass(&wc);

// 创建窗口
hWnd = CreateWindow(szClassName, szWindowName, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL);

ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);

// 消息循环
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}

pEvntLog->WriteEvnt("Quitting...");

delete pProgram;
delete pEvntLog;

return msg.wParam;
}



LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{

switch (message)
{
case WM_DESTROY:
pEvntLog->WriteEvnt("WM_DESTROY");
PostQuitMessage(0);
break;

case WM_QUERYENDSESSION:
if (lParam & ENDSESSION_LOGOFF) {
pEvntLog->WriteEvnt("LOGOFF");
}
else {
pEvntLog->WriteEvnt("SHUTDOWN");
}
// delete pProgram;
// delete pEvntLog;
DestroyWindow(hWnd);
return TRUE;


default:
return DefWindowProc(hWnd, message, wParam, lParam);
}

return 0;
}

程序在WinMain开头new了两个对象，本来指望在WinMain结尾，也就是消息循环结束后delete掉。但是这个delete过程在我正常关闭窗口时是可以执行的，注销（或关机）时候却无法正常执行。

注销（或关机）时候，程序先处理了WM_QUERYENDSESSION消息，执行了DestroyWindow，然后也正常处理了WM_DESTROY消息，这在程序的日志上可以看到，按理说PostQuitMessage后消息循环就应该终止了，然后程序正常delete对象，正常终止，但是事实上却没有delete。百思不得其解...

[沙老师]

高手怎么都这么吝啬阿。。。我只希望程序在注销时候能够正常退出（就是能够执行到“
pEvntLog->WriteEvnt("Quitting...");

delete pProgram;
delete pEvntLog;

return msg.wParam;
}

”）这个地方，不可能做到吗？

[沙老师]

解决问题的100分奉送！

[goodboyws]

在delete 之前已经关机了

[goodboyws]

from MSDN
.....
When an application returns TRUE for this message, it receives the WM_ENDSESSION message and it is terminated, regardless of how the other applications respond to the WM_QUERYENDSESSION
因为你返回TRUE,系统会terminate你的进程，所以你的对象来不及释放

[沙老师]

from MSDN
.....
When an application returns TRUE for this message, it receives the WM_ENDSESSION message and it is terminated, regardless of how the other applications respond to the WM_QUERYENDSESSION
因为你返回TRUE,系统会terminate你的进程，所以你的对象来不及释放
==========================================================
刚才试了，return FALSE 照样不行，系统可以注销，但是对象仍旧没有释放。如果将DestroyWindow改成CloseWindow，还是return FALSE ，那么系统不可以注销，窗口在注销的时候只是最小化而不关闭，呵呵。

[goodboyws]

呵呵，问题在这里，DestroyWindow是不可以用在消息循环内部的，直接用PostQuitMessage(0);就可以
case WM_QUERYENDSESSION:
if (lParam & ENDSESSION_LOGOFF) {
pEvntLog->WriteEvnt("LOGOFF");
}
else {
pEvntLog->WriteEvnt("SHUTDOWN");
}
//delete pProgram;
//delete pEvntLog;
PostQuitMessage(0);
return TRUE;

[goodboyws]

好像不是这个问题，汗！

[Elysium]

只在本进程内有效

[yjgx007]

I think you are mistake to process window's default procedure.

Please move that code in 'switch' section as below to last line of WndProc(...)
======================================================
return DefWindowProc(hWnd, message, wParam, lParam);

[hanjk]

你在DestroyWindow(hWnd)之前不是已经delete了吗

[沙老师]

正常关闭窗口和注销都能够执行到WM_DESTROY消息啊...

[沙老师]

upupupup

[沙老师]

case WM_QUERYENDSESSION:
if (lParam & ENDSESSION_LOGOFF) {
pEvntLog->WriteEvnt("LOGOFF");
}
else {
pEvntLog->WriteEvnt("SHUTDOWN");
}
// DestroyWindow(hWnd);
PostQuitMessage(0);
return TRUE;

试过了，还是不行。另外，DestroyWindow应该可以用在消息循环内部，它发出WM_DESTROY消息，然后在WM_DESTROY处理里调用PostQuitMessage发出WM_QUIT消息退出消息循环。

[jazy]

The application need not call the DestroyWindow or PostQuitMessage function when the session is ending.

你的代码为什么要注释那两个delete？原先不是合理的吗？
case WM_QUERYENDSESSION:
if (lParam & ENDSESSION_LOGOFF) {
pEvntLog->WriteEvnt("LOGOFF");
}
else {
pEvntLog->WriteEvnt("SHUTDOWN");
}
delete pProgram;
delete pEvntLog;
return TRUE;

[沙老师]

to jazy():

我的初衷是无论按关闭按钮还是注销，都能够停止消息循环进而执行循环下面的语句。但是现在发现注销时候不行，而且问题越来越奇怪。

[jazy]

case WM_QUERYENDSESSION:
if (lParam & ENDSESSION_LOGOFF) {
pEvntLog->WriteEvnt("LOGOFF");
}
else {
pEvntLog->WriteEvnt("SHUTDOWN");
}
delete pProgram;
delete pEvntLog;
这里的delete走不到吗？不应该啊，return之前注销操作是在等待的

[沙老师]

to jazy():

这里可以走的，但是为什么执行不了消息循环下面的语句呢？

[jazy]

因为你在
case WM_QUERYENDSESSION:
的最后
return TRUE;

WM_QUERYENDSESSION消息的处理一旦return，就关机了，要做什么操作，在return之前做