Why does CWnd::GetSafeOwner return null ?

Question

Why does CWnd::GetSafeOwner return null ?

Suzuki Masato 1

OS:Windows 10 Pro 21H2 19044.1766
Browser:Edge 103.0.1264.44 Use IE Mode
Application: ActiveX (C++/MFC OCX 32bit)
Visual Studio 2019

Problem
①Launch browser. Show web page(page1).
②Click Button of page1.(Using window.open API of JavaScript)
③Show another web page(page2).(Page containing ActiveX)
④CWnd::GetSafeOwner called inside ActiveX returns a valid window handle.
⑤Then close the web page(page2).(Using window.close API of JavaScript)
⑥Click Button of page1 again.(Using window.open API of JavaScript)(Show web page2 again).
⑦This time CWnd::GetSafeOwner called inside ActiveX returns null.

I want to know why CWnd::GetSafeOwner returns null for the second time.

Viorel 127K Reputation points

2022-07-07T07:59:00.707+00:00

Which arguments did you pass to GetSafeOwner?
Suzuki Masato 1 Reputation point

2022-07-07T08:48:10.907+00:00

No parameters specified.

Code ：
CWnd* pOwnerWnd = CWnd::GetSafeOwner();
YujianYao-MSFT 4,296 Reputation points Microsoft External Staff

2022-07-07T09:22:48.57+00:00

Hi @Suzuki Masato ,

Could you please provide a minimal executable program that reproduces the problem? This helps everyone understand the problem.
Viorel 127K Reputation points

2022-07-07T10:28:35.4+00:00

Did you also check the Internet Explorer (if available)?
Suzuki Masato 1 Reputation point

2022-07-07T23:42:49.02+00:00

Yes. It was the same behavior.

Additional Information:
It worked fine using the debug build module.
YujianYao-MSFT 4,296 Reputation points Microsoft External Staff

2022-07-08T08:21:03.833+00:00
Hi @Suzuki Masato ,

The MFC code is:

_AFXWIN_INLINE HWND CWnd::GetSafeHwnd() const { return this == NULL ? NULL : m_hWnd; }

It can be seen that when this is NULL, the function will return NULL.

Does the problem you mentioned only occur in release mode?
Suzuki Masato 1 Reputation point

2022-07-08T08:42:37.24+00:00

Yes. only occur in release build.
YujianYao-MSFT 4,296 Reputation points Microsoft External Staff

2022-07-11T06:36:31.92+00:00

Hi @Suzuki Masato ,

Release and debug use different project properties, I suggest you test with the same project properties in release and debug mode.