Strncmp and GetwindowText problem

[keret]

I enumerate all open windows with Enumwindows. In the processor function I try to check if the title of the window contains a certain string. If yes, put the handle in a list of handles(m_wndList).

if(hwnd)
{
CWindow win(hwnd);
CHAR str[100];
win.GetWindowText((LPTSTR)(str),100);
if (strncmp(str,"searchstring", 13) == 0)
dlg->m_wndList.push_back(hwnd);
}

It compiles, but I get the following error messages: Run-time Check Failure #2: Stack around the variable str is corrupted and/or Run-time Check Failure #2: Stack around the variable win is corrupted What is the problem? How should I change my code?

[Stephen Hewitt]

There's some problems with your code. What's with the (LPTSTR) nonsense? My guess is that you're building a Unicode application and casting away the compiler warnings (the (LPTSTR) cast I mentioned before) which were informing you of the real problem: that CHAR str[100]; is not a Unicode string. Try this:

if(hwnd)
{
CWindow win(hwnd);
TCHAR str[100];
win.GetWindowText(str, 100);
if (_tcsncmp(str, _T("searchstring"), 13) == 0)
dlg->m_wndList.push_back(hwnd);
}

Don't cast unless you're sure what the cast actually means, and don't try to cast away error messages.

Steve

[Cedric Moonen]

To complement the answer from Stephen, I suggest you read this excellent article[^]. You'll be able to really understand why your code is wrong.

[keret]

Thanks guys, you both helped me a lot. At the moment I just cut & paste any code I find, but this will change I hope.

[David Crow]

keret wrote:

if (strncmp(str,"searchstring", 13) == 0)

Why 13?

"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown

"The brick walls are there for a reason...to stop the people who don't want it badly enough." - Randy Pausch

[keret]

I had an other searchstring originally. :)