[Bug 59396] dispatch_user_callback ignores handled SEH EXCEPTION_ACCESS_VIOLATION (c0000005) in 32-bit WndProc, breaking MFC/ToolkitPro MDI tab initialization

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=59396

[e-mail] changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Tabbed UI in proprietary    |dispatch_user_callback
                   |IDE broken after update –   |ignores handled SEH
                   |tabs are shown as separate  |EXCEPTION_ACCESS_VIOLATION
                   |windows                     |(c0000005) in 32-bit
                   |                            |WndProc, breaking
                   |                            |MFC/ToolkitPro MDI tab
                   |                            |initialization
            Version|11.1                        |11.6

--- Comment #2 from [e-mail] ---
Summary

When a 32-bit MFC application uses SEH (__try/__except) to handle an
EXCEPTION_ACCESS_VIOLATION (0xc0000005) inside a Windows callback (WndProc),
Wine's dispatch_user_callback logs ignoring exception c0000005 and does not
pass control to the SEH handler. On Windows the exception is caught correctly,
the MDI/tab layout initializes, and documents open in tabs. Under Wine the MDI
client window never properly initializes and all documents open as floating
windows instead of tabs.

Steps to reproduce

Minimal reproduction with a 32-bit MFC + Codejock ToolkitPro application
compiled with MSVC 2019 / mfc140.dll. The new code path calls msvcp140.dll code
at RVA 0x157C3 from within a WndProc, which reads a NULL pointer intentionally
(pattern: __try { *ptr } __except(EXCEPTION_EXECUTE_HANDLER) { ... initialize
... }). On Windows the __except block runs as expected.

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