GDI Resource Leak - visual-c++

Question

I have found a GDI leak in our huge application software.
Below is a simple program to test this problem.
The Idea is that the main dialog box opens another dialog box(dialog box A).
If the dialog box A include a bitmap function for a CStatic control,
it will create GDI leak.
Even when I use "DeleteObject(bitmap)".
Have I done some thing wrong ?
Do you have any thoughts?
Thanks.
// Resource File
...
DIALOG_BOXA DIALOGEX 0, 0, 219, 142
STYLE DS_SETFONT | DS_FIXEDSYS | WS_POPUP | WS_VISIBLE | WS_BORDER
EXSTYLE WS_EX_STATICEDGE
FONT 8, "MS Shell Dlg", 400, 0, 0x1
BEGIN
DEFPUSHBUTTON "OK",IDOK,46,121,50,14
PUSHBUTTON "Cancel",IDCANCEL,119,121,50,14
CONTROL 131,RED_LIGHT0,"Static",SS_BITMAP,7,17,80,37
PUSHBUTTON "",RED_LIGHT1,7,60,80,37,BS_BITMAP | NOT WS_TABSTOP
END
// head file
DialogBoxA: public CDialog
{
...
CStatic m_static;
CButton m_button ;
...
}
/////////////////////////////////////////////////////////
void DialogBoxA::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
DDX_Control(pDX, RED_LIGHT0, m_static);
DDX_Control(pDX, RED_LIGHT1, m_button);
}
BOOL DialogBoxA::OnInitDialog()
{
CDialog::OnInitDialog();
HBITMAP bitmap ;
// This will create GDI leak !!!
bitmap = LoadBitmap ( AfxGetApp()->m_hInstance,BEACON_BIG_RED_ON) ;
m_static.SetBitmap (bitmap );
DeleteObject(bitmap);
// This is OK !!!
bitmap = LoadBitmap ( AfxGetApp()->m_hInstance,BEACON_BIG_RED_ON) ;
m_button.SetBitmap (bitmap );
DeleteObject(bitmap);
return TRUE; // return TRUE unless you set the focus to a control
// EXCEPTION: OCX Property Pages should return FALSE
}

Answer 1

Here is the exlanantion and solution for the GDI leak in static control:
http://blogs.msdn.com/b/oldnewthing/archive/2014/02/19/10501282.aspx

Answer 2

It's complicated. First, let's take a closer look at your code
bitmap = LoadBitmap ( AfxGetApp()->m_hInstance,BEACON_BIG_RED_ON) ;
m_static.SetBitmap (bitmap );
DeleteObject(bitmap);
You should not delete the bitmap that you just told the static control to use. It's still using it! It's going to continue using it until you set the bitmap to something else.
So instead of trying to delete the bitmap during dialog initialization, you should wait until the dialog is being destroyed. At that point, you have to get tell the static control to stop using the bitmap, and only then can you delete the bitmap object.
Second, static controls sometimes make a copy of your bitmap. Whether it makes a copy depends on a bunch of things, including whether the bitmap has a non-zero alpha channel. It becomes your problem to destroy this copy as well. (This may be why your one of your cases works and the other doesn't.)
You basically have to keep track of the bitmap you think you set until it's time to clean up. Then you have to compare what's actually in the static control to the one you thought you gave it. If they're different, then you destroy both (your bitmap and the static controls copy). If they're the same, then the static control didn't make a copy, and you have to destroy just the one you made (once!).