Strange: GetMessage keeps returning message

Hi There,

The following codes keeps returning messages even nothing is preesed in the keyboard and mouse is not moved and touched.

Code:

    
     while ( bRet = GetMessage (&msg, NULL, 0, 0))
     {
          bRet = TranslateMessage (&msg) ;
          if (0 == bRet)
               MessageBox (NULL, TEXT ("Error: GetMessage return 0!"), 
                      szAppName, MB_ICONERROR) ;
          DispatchMessage (&msg) ;
     }

Three returns are:

Code:

 
meg        1st                       2nd                      3rd
hwnd       0x00000000       0x00000000       0x00000000
message 49368                 49368                 49368
wParam  17                        17                      17
lParam    657624                854138              1050746
time       143047484           143249515        143362468
pt           {x=830 y=237}    {x=653 y=563} {x=611 y=561}

For these messages, TranslateMessage returns 0.

The OS is Windows 2000 with Service pack 4 or Windows XP with service pack 2.

What're these message? Where are they from?

Note about TranslateMessage Return Value

If the message is translated (that is, a character message is posted to the thread's message queue), the return value is nonzero.

If the message is WM_KEYDOWN, WM_KEYUP, WM_SYSKEYDOWN, or WM_SYSKEYUP, the return value is nonzero, regardless of the translation.

If the message is not translated (that is, a character message is not posted to the thread's message queue), the return value is zero.

Thanks,

1st, GetMessage returns -1, not 0, to indicate an error see GetMessage

2nd, there are no system generated messages in the range 49368. Are you sending messages to the window somewhere else in your code or maybe a custom control?

3rd, HWND of 0 is not a valid window, or maybe the desktop, maybe you should post more of your code.

Originally Posted by Darryl

1st, GetMessage returns -1, not 0, to indicate an error see GetMessage

2nd, there are no system generated messages in the range 49368. Are you sending messages to the window somewhere else in your code or maybe a custom control?

3rd, HWND of 0 is not a valid window, or maybe the desktop, maybe you should post more of your code.

Thanks Darryl for your quick response.

All three return results from GetMessage are 1, and all three results from TranslateMessage are 0. All three hwnd is 0, that's right (get all message from all windows of the thread).

That's the question, what's the message 49368? Where they come from? I don't know any program in the system keep sending the message. They are tested on both 2000 and XP, two completely different systems, even there is no any other app is running except the test one.

Thanks,

Ok I just tried this on my system and got nothing

Code:

MSG msg;
     int rtn;
     while((rtn=GetMessage(&msg, NULL, 0, 0)) != 0)
     {
          if (msg.message == 49368)
          {
               ::MessageBox(0,TEXT("Hello"),TEXT("Hello"), MB_OK);
          }
          if (rtn == -1)
          {
               return ::GetLastError();
          }
          else 
               if (!IsDialogMessage(swinc::SwincWindowBase::g_current_dialog_hwnd, &msg))
               {
                    TranslateMessage(&msg);
                    DispatchMessage(&msg);
               }
     }

Maybe you can run something like spy++ or better win inspector spy and try and trace the message

I have no solution for your problem
but you should check return value - before checking the msg contents...
If GetMessage failed - msg contents will be probably invalid

Good idea, Darryl. Can you tell how I can use Spy++ to trace where is the message come from? I launch Spy++ but get no clue how it can be used.

Thanks,

Ok on MSDN that number falls in the range:

0xC000 through 0xFFFF String messages for use by applications.

Message numbers in the fourth range (0xC000 through 0xFFFF) are defined at run time when an application calls the RegisterWindowMessage function to retrieve a message number for a string. All applications that register the same string can use the associated message number for exchanging messages. The actual message number, however, is not a constant and cannot be assumed to be the same between different sessions.

I change the codes to the following:

Code:

     while ( bRet = GetMessage (&msg, NULL, 0, 0))
     {
          bRet = TranslateMessage (&msg) ;
		  if (0 == bRet) {
               wsprintf (szBuffer, TEXT("Error: Message: 0x%x %u, wParam: %u, lParam:0x%08x"),
				          msg.message, msg.message, msg.wParam, msg.lParam);
               MessageBox (NULL, szBuffer, szAppName, MB_ICONERROR) ;
		  }
          DispatchMessage (&msg) ;
     }

This time the message number changes to: 0xcobd, i.e., 49341. For every click on the OK on the dialog box, the lParam beeps increasing as the following:

1st
---------------------------
KeyView1
---------------------------
Error: Message: 0xc0bd 49341, wParam: 17, lParam:0x00b208f4
---------------------------
OK
---------------------------
2nd
---------------------------
KeyView1
---------------------------
Error: Message: 0xc0bd 49341, wParam: 17, lParam:0x00b308f4
---------------------------
OK
---------------------------
3rd
---------------------------
KeyView1
---------------------------
Error: Message: 0xc0bd 49341, wParam: 17, lParam:0x00b408f4
---------------------------
OK
---------------------------
4th
---------------------------
KeyView1
---------------------------
Error: Message: 0xc0bd 49341, wParam: 17, lParam:0x00b508f4
---------------------------
OK
---------------------------
5th
---------------------------
KeyView1
---------------------------
Error: Message: 0xc0bd 49341, wParam: 17, lParam:0x00b608f4
---------------------------
OK
---------------------------
6th
---------------------------
KeyView1
---------------------------
Error: Message: 0xc0bd 49341, wParam: 17, lParam:0x00b708f4
---------------------------
OK
---------------------------


My desktop computer seems running normal if I do not run this small piece of codes or if check from TranslateMessage is removed. I do every thing as usual.
Thanks,

I am curious, why are you checking the return on translate message anyway? 0 does not indicate error, only that the message was not translated, ie. not a character message.

I step through some code of mine in the debugger and was getting message of similar value. As I stated in the other post, this range is for privately registered messages. If I had to guess, I would say some system component is sending out broadcast messages. I would just ignore it.

You know, it uses and occupies a lot of system time and resources, slows down its response and sometime causes application collapse. How do I notice it exists? One of my app crashes at it.

Is it a computer virus? What reason for a valid app keeps generating these nonsense messages?

Thanks,

Interesting that the lParams are all the max storage size of an int32 apart.

Try following the msg into the dialog. It may be background window msgs.

Does IsDialogMessage() process it?

if your application is crashing becuase it is receiving a broadcast message that it doesnt know how to handle, then the problem is that your application is not properly handling messages. Any message that your application does not specifically handle needs to be passed to DefWndProc(). This message is probably an auto-discovery message for applications in a suite or sometimes peeps will broadcast a message as a way of ensuring that every thread in their application recieves the message. Its sloppy coding, but its easier than maintaining an internal list of every hwnd of every thread in your application. As long as you arent sending a lot of broadcasts, it shouldnt degrade system performance noticeably, btu it is still a kludge.

Originally Posted by novacain

Interesting that the lParams are all the max storage size of an int32 apart.

Dont you mean int16 ?

Opps

It collapses at the inside of TranslateMessage: illegal instruction. I have no idea what's going on inside of the function, and why it crashes. So I try to check the return from it but fail because of the nonsence message keeping coming.

Thanks,

Originally Posted by wow

It collapses at the inside of TranslateMessage: illegal instruction.

How do you come to this conclusion? TranslateMessage, either translates or doesn't, it doesn't return any errors.

Just to test, comment out TranslateMessage, (unless your app relies on keyboard input), and see if your app still crashes.