How to solve error: Heap block at 007A8530 modified at 007A860A past requested size of d2?

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I am a newbie to C++. I was trying to convert the function here to set html unicode text to clipboard. This is what I have done so far:

C++

bool CopyHTML2(WCHAR *html ){
    wchar_t *buf = new wchar_t [400 + wcslen(html)];
    if(!buf) return false;

	static int cfid = 0;
    if(!cfid) cfid = RegisterClipboardFormat("HTML Format");

	    // Create a template string for the HTML header...
    wcscpy(buf,
        L"Version:0.9\r\n"
        L"StartHTML:00000000\r\n"
        L"EndHTML:00000000\r\n"
        L"StartFragment:00000000\r\n"
        L"EndFragment:00000000\r\n"
        L"<html><body>\r\n"
        L"<!--StartFragment -->\r\n");

    // Append the HTML...
    wcscat (buf, html);
    wcscat (buf, L"\r\n");
    // Finish up the HTML format...
    wcscat (buf,
        L"<!--EndFragment-->\r\n"
        L"</body>\r\n"
        L"</html>");

	wchar_t *ptr = wcsstr(buf, L"StartHTML");
	wsprintfW(ptr+10, L"%08u", wcsstr(buf, L"<html>") - buf);
	*(ptr+10+8) = L'\r';

    ptr = wcsstr(buf, L"EndHTML");
    wsprintfW(ptr+8, L"%08u", wcslen(buf));
    *(ptr+8+8) = '\r';

    ptr = wcsstr(buf, L"StartFragment");
    wsprintfW(ptr+14, L"%08u", wcsstr(buf, L"<!--StartFrag") - buf);
    *(ptr+14+8) = '\r';

    ptr = wcsstr(buf, L"EndFragment");
    wsprintfW(ptr+12, L"%08u", wcsstr(buf, L"<!--EndFrag") - buf);
    *(ptr+12+8) = '\r';

	// Open the clipboard...
    if(OpenClipboard(0)) {
        EmptyClipboard();
        HGLOBAL hText = GlobalAlloc(GMEM_MOVEABLE |GMEM_DDESHARE, wcslen(buf)+4);
        wchar_t *ptr = (wchar_t *)GlobalLock(hText);
        wcscpy(ptr, buf);
        GlobalUnlock(hText);
        SetClipboardData(cfid, hText);
        CloseClipboard();
        GlobalFree(hText);
    }

    // Clean up...
    //delete [] buf;
	return true;
}

I get the following error at SetClipboardData function:

HEAP[Project1.exe]: Heap block at 00378038 modified at 0037813E past requested size of fe
Project1.exe has triggered a breakpoint.

Any idea on how to solve this? Also is it the right way to do this? Or is there a simpler way to do it?

Thanks in advance for all your help.

Posted 12-Apr-13 19:35pm

madharasan1

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Richard MacCutchan 13-Apr-13 4:36am

All the code from the line wsprintfW(ptr+8, L"%08u", wcslen(buf)); is impossible to understand, but looks very likely to cause corruption. Start again in building your buffer but make sure that at every point you do not overflow it.

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Jochen Arndt · Accepted Answer · 2013-04-12T23:22:00

I did not see the source for the heap error but you also asked for the right or simpler way. At first you should know that the HTML clipboard format must contain UTF-8 encoded text. So the input text must be converted to UTF-8 and prefixed with the HTML format header. A snippet from one of my projects (lpszWide is the HTML text as wide string including the HTML and fragment start and end markers):

// Get length of UTF-8 string including terminating NULL char.
// The MSDN does not mention if the string should be NULL terminated or not.
// Providing the NULL terminator is safe and always better.
int nUtf8Size = ::WideCharToMultiByte(CP_UTF8, 0, lpszWide, -1, NULL, 0, NULL, NULL);
if (nUtf8Size < 1)
{
    TRACE0("CHtmlFormat::SetHtml: UTF-8 conversion failed\n");
    ASSERT(0);
    return false;
}
// Allocate buffer for HTML format descriptor and UTF-8 content. 
// NOTE: Adjust length definition when changing the descriptor!
const int nDescLen = 105;
hGlobal = ::GlobalAlloc(GMEM_MOVEABLE, nDescLen + nUtf8Size);
if (NULL != hGlobal)
{
    // Convert to UTF-8
    bool bErr = false;
    LPSTR lpszBuf = static_cast<LPSTR>(::GlobalLock(hGlobal));
    LPSTR lpszUtf8 = lpszBuf + nDescLen;
    if (::WideCharToMultiByte(CP_UTF8, 0, lpszWide, -1, lpszUtf8, nUtf8Size, NULL, NULL) <= 0)
    {
        TRACE0("CHtmlFormat::SetHtml: UTF-8 conversion failed\n");
        bErr = true;
    }
    else
    {
        // Get the fragment marker positions
        LPCSTR lpszStartFrag = strstr(lpszUtf8, "<!--StartFragment-->");
        LPCSTR lpszEndFrag = strstr(lpszUtf8, "<!--EndFragment-->");
        ASSERT(lpszStartFrag);
        ASSERT(lpszEndFrag);
        // Adjust pointer to be behind inserted string followed by CR-LF
        lpszStartFrag += strlen("<!--StartFragment-->") + 2;
        // Create descriptor and prepend it to the string.
        // Use only ASCII chars here!
        // Using leading zeroes with the offsets here to avoid iterative calculations.
        // With valid nDescLen, _snprintf() will not append the NULL terminator here.
        VERIFY(nDescLen == _snprintf(
            lpszBuf, nDescLen,
            "Version:1.0\r\nStartHTML:%010d\r\nEndHTML:%010d\r\nStartFragment:%010d\r\nEndFragment:%010d\r\n",
            nDescLen, 
            nDescLen + nUtf8Size - 1,		// offset to next char behind string
            nDescLen + static_cast<int>(lpszStartFrag - lpszUtf8), 
            nDescLen + static_cast<int>(lpszEndFrag - lpszUtf8)));
    }
    ::GlobalUnlock(hGlobal);
    if (bErr)
    {
        ::GlobalFree(hGlobal);
        hGlobal = NULL;
    }
}
return NULL != hGlobal;