using sendmessage to send wm_close to another process

Question

I want to send wm_close to another process, with which i want end that process safely.

int _tmain(int argc, _TCHAR* argv[])
{

    DWORD SetOfPID;
    SetOfPID = GetProcId(_T("abc.exe"));  //this will return pid
    HANDLE h = OpenProcess(PROCESS_ALL_ACCESS,false, SetOfPID);

    HWND hwnd = ::GetTopWindow(NULL);
    while(hwnd)
    {
        DWORD pid;
        DWORD dwThreadId = ::GetWindowThreadProcessId(hwnd, &pid);
         if(pid == SetOfPID)
         {    
              break;
         }
         hwnd = ::GetNextWindow(hwnd, GW_HWNDNEXT);
    }
    //DestroyWindow(hwnd);
    bool temp = IsWindow(hwnd); **//this gives true**
    LRESULT res = ::SendMessage(hwnd, WM_CLOSE, NULL, NULL);
    DWORD err = GetLastError(); **//this gives 6**
    CloseHandle(hwnd);
    CloseHandle(h);
    return 0;
}

this piece of code looks good, but the target process doesn't terminate, can somebody help me?

Why are you opening the process? That seems unnecessary. Error 6 means an invalid handle. You shouldn't call CloseHandle on a window handle. You don't need to tidy up the window handle, it's not a HANDLE. — David Heffernan, Mar 23 '11 at 07:52
i was trying something else, so opening process is part of that. And i know error 6. You shouldn't call CloseHandle on a window handle --> thanks alot for this. — rplusg, Mar 23 '11 at 08:23
Sending the WM_CLOSE message to the main form of an app does result in it closing, if that window responds to WM_CLOSE. I can't imagine what you are doing wrong. My recommendation is to use Spy++ to check that you have located the right window handle. — David Heffernan, Mar 23 '11 at 09:42

score 3 · Answer 1 · edited Jun 20 '20 at 09:12

I would attempt to close a (Process with) Window(s) in the following order:

WM_CLOSE

WM_QUIT

WM_DESTROY

TerminateProcess().

Just my take as I am handling (disabling) WM_CLOSE for a Window and having difficulty distinguishing between User Close and close messages send by another master task. WM_QUIT seems to resolve my problem without using a custom WM_APP_CLOSE of my own. TerminateProcess is very much a last resort unclean exit to be avoided at all costs (it may leave handles (e.g. COM etc) and memory etc unfreed).

score 2 · Accepted Answer · answered Mar 23 '11 at 08:16

2

Are you sure that the window you are finding is the correct one? You can check easily with Spy++. Moreover, when searching for a window, I think it's better to use EnumWindows. I'm not sure your method is correct.

answered Mar 23 '11 at 08:16

pagra

665
4
11

IsWindow() returns true, doesn't it mean i've a valid window? – rplusg Mar 23 '11 at 08:27
1

@rplusg: IsWindow tells you it is a valid window handle, not more. It can be that the application has got several top level windows, maybe not visible. And you may not close the right one. – pagra Mar 23 '11 at 12:29
even i'm not sure what is the problem, but enumwindows has given my desired results. Thanks patriiice, marking your answer as final. – rplusg Mar 28 '11 at 08:00

score 0 · Answer 3 · answered Mar 23 '11 at 08:17

0

If the application does not process WM_CLOSE the DefWindowProc should handle this (by gracefully closing the application), however if the application is handling WM_CLOSE then it simply can choose to ignore it. Try sending the WM_DESTROY and WM_NCDESTROY messagees instead.

answered Mar 23 '11 at 08:17

Ferenc Deak

34,348
17
99
167

WM_DESTROY and WM_NCDESTROY also doesn't work. DestroyWindow() also returns false. – rplusg Mar 23 '11 at 08:26
1

WM_DESTROY and WM_NCDESTROY can't work, they are notifications. – David Heffernan Mar 23 '11 at 09:31

using sendmessage to send wm_close to another process

3 Answers3

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