Strange problem with VirtualAllocEx

This is a discussion on Strange problem with VirtualAllocEx within the Windows Programming forums, part of the Platform Specific Boards category; Salutations, I'm experiencing a strange problem with Visual C++ 2010 and Visual C++ 6.0. I have the following piece of ...

  1. #1
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    Strange problem with VirtualAllocEx

    Salutations,

    I'm experiencing a strange problem with Visual C++ 2010 and Visual C++ 6.0. I have the following piece of code:
    Code:
    hWnd = FindWindow("Progman", NULL);
    if (NULL != hWnd) hWnd = FindWindowEx(hWnd, NULL, "SHELLDLL_DefView", NULL);
    if (NULL != hWnd) hWnd = FindWindowEx(hWnd, NULL, "SysListView32", NULL);
    if (NULL != hWnd)
    {
    	DWORD pid;
    	GetWindowThreadProcessId(hWnd, &pid);
    	HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, 0, pid);
    	RECT* ptritemrect;
    	RECT itemrect;
    	ptritemrect = (RECT*)VirtualAllocEx(hProcess, NULL, sizeof(RECT), MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
    	if (ptritemrect == NULL) {
    		DWORD error = GetLastError();
    		char cavalo[10];
    		sprintf(cavalo, "%i", error);
    		MessageBox(w, cavalo, "", 0);
    	} else {
    		SendMessage(hWnd, LVM_GETITEMRECT, 0, (LPARAM)ptritemrect);
    		DWORD copied = 0;
    		ReadProcessMemory(hProcess, (void*)ptritemrect, (LPVOID)&itemrect, sizeof(itemrect), &copied);
    		VirtualFreeEx(hProcess, ptritemrect, 0, MEM_RELEASE);
    	}
    }
    The problem is this: I've tried to compile this code in Visual C++ 2010 (at Windows 7) and in Visual C++ 6 (at Windows XP Professional SP3).
    The code compiled with Visual C++ 6 works on both computers. But the code compiled with Visual C++ 2010 works only on Windows 7, not on Windows XP. On Windows XP, VirtualAllocEx doesn't work and ptritemrect gets the value NULL.
    The function GetLastError() accuses error code 6, which means "The handle is invalid.".
    I have no idea on why it works in Windows 7 and Windows XP when compiled with Visual C++ 2010, while it works on both when compiled with Visual C++ 6.
    Any ideas?

    Thank you in advance.

  2. #2
    and the hat of wrongness Salem's Avatar
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    How about reading the manual?

    Process Security and Access Rights (Windows)
    Quote Originally Posted by msdn
    PROCESS_ALL_ACCESS All possible access rights for a process object.

    Windows Server 2003 and Windows XP/2000: The size of the PROCESS_ALL_ACCESS flag increased on Windows Server 2008 and Windows Vista. If an application compiled for Windows Server 2008 and Windows Vista is run on Windows Server 2003 or Windows XP/2000, the PROCESS_ALL_ACCESS flag is too large and the function specifying this flag fails with ERROR_ACCESS_DENIED. To avoid this problem, specify the minimum set of access rights required for the operation. If PROCESS_ALL_ACCESS must be used, set _WIN32_WINNT to the minimum operating system targeted by your application (for example,
    #define _WIN32_WINNT _WIN32_WINNT_WINXP
    ). For more information, see Using the Windows Headers.
    Paying attention to return values would help as well.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  3. #3
    'Allo, 'Allo, Allo
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    Wow, talk about making a molehill into a mountain.

    Code:
    RECT workArea;
    SystemParametersInfo(SPI_GETWORKAREA, 0, &workArea, 0);
    That's it. Now it'll work whenever the order of the windows change, like they did in Win7.

  4. #4
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    Quote Originally Posted by Salem View Post
    How about reading the manual?

    Paying attention to return values would help as well.
    Thank you, I put
    Code:
    #define _WIN32_WINNT _WIN32_WINNT_WINXP
    at the top and it works now.
    You are right, I should have checked the return value of OpenProcess.
    I don't know why I was in such a hurry to send this question.
    I've obviously wasted your time.
    Quote Originally Posted by adeyblue View Post
    Wow, talk about making a molehill into a mountain.
    Code:
    RECT workArea;
    SystemParametersInfo(SPI_GETWORKAREA, 0, &workArea, 0);
    That's it. Now it'll work whenever the order of the windows change, like they did in Win7.
    Yes, I use the code you mentioned, but for a different thing.
    Last edited by pc2-brazil; 02-17-2011 at 03:25 PM.

  5. #5
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    pc-2 Brazil.... Ok, I'm stumped... what does this code do???

    That is, I can follow each step... but what's the overall effect?

  6. #6
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    Quote Originally Posted by CommonTater View Post
    pc-2 Brazil.... Ok, I'm stumped... what does this code do???

    That is, I can follow each step... but what's the overall effect?
    Actually, I've written this part in a simplified way, but it should have the following line after taking getting the desktop ListView handler:
    Code:
    int count = ListView_GetItemCount(hWnd);
    It counts the number of icons of the desktop.
    Then, the whole part from the call to VirtualAllocEx on should be inside a loop, and the line
    Code:
    SendMessage(hWnd, LVM_GETITEMRECT, 0, (LPARAM)ptritemrect);
    should be:
    Code:
    SendMessage(hWnd, LVM_GETITEMRECT, i, (LPARAM)ptritemrect);
    where i is an index from 0 to count - 1. Actually, it loops through every icon in the desktop and gets its rectangle.
    Anyway, the problem is solved already, and it was that I should have checked the every return value.

  7. #7
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    Ahh.. makes sense now.

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