Exceptions silently caught by Windows, how to handle manually?

After browsing similar questions I stumbled across this answer: OpenGL suppresses exceptions in MFC dialog-based application

"Ok, I found out some more information about this. In my case it's windows 7 that installs KiUserCallbackExceptionHandler as exception handler, before calling my WndProc and giving me execution control. This is done by ntdll!KiUserCallbackDispatcher. I suspect that this is a security measure taken by Microsoft to prevent hacking into SEH.

The solution is to wrap your wndproc (or hookproc) with a try/except frame."

I've filed a bug report with Microsoft, you can see their response here:
http://connect.microsoft.com/VisualStudio/feedback/details/550944/hardware-exceptions-on-x64-machines-are-silently-caught-in-wndproc-messages

From Microsoft:

Thanks for the report. I've found out that this is a Windows issue, and there is a hot fix available. Please see http://support.microsoft.com/kb/976038 for a fix that you can install if you wish.

functions that may be of interest:

SetUnhandledExceptionFilter()
_set_invalid_parameter_handler()
_RTC_SetErrorFuncW()
_CrtSetReportHookW2()

PS, be aware that SetUnhandledExceptionFilter() can be overriden by other dlls loaded into your .exe. eg, flash and nvidia direct3d do this. I use api hooking to cure this.

I experienced this same issue, and found it was a result of this Microsoft bug: http://connect.microsoft.com/VisualStudio/feedback/details/550944/hardware-exceptions-on-x64-machines-are-silently-caught-in-wndproc-messages

There’s a fix available from Microsoft, though deploying it is somewhat challenging if you have multiple target platforms:

http://support.microsoft.com/kb/976038

Here's an article on the subject describing the behavior:

http://blog.paulbetts.org/index.php/2010/07/20/the-case-of-the-disappearing-onload-exception-user-mode-callback-exceptions-in-x64/

The issue is basically that Hardware exceptions in 32-bit programs are silently caught in the WndProc routine on 64-bit OSs, unless you send commands telling it not to. Microsoft has a hotfix for the issue that is required if you're running Vista SP2, but isn't required with Windows 7 SP1 (not sure about Win7 without the SP).

Even WITH the hotfix, you need to enable the correct behavior by setting a registry key or making some calls to the kernel to tell it your process expects hardware exceptions to crash when encountered during WndProc.

According to the PaulBetts link above, this was done for backwards compatibility with Windows Server 2003.

If you program is a 64-bit program, this issue goes away.

ANSWER IN HINDSIGHT for anyone who stumbles upon this later.

This was caused by a known issue in Windows http://support.microsoft.com/kb/976038 - make sure you're up to date, install the hotpatch if you need to, and mark your application as Windows 7 compatible. http://msdn.microsoft.com/en-us/library/dd371711%28v=vs.85%29.aspx

I've seen this with exception codes c015000f and c0150010.

You can force Windows to not ignore the exceptions with this code snippet (from Microsoft's Exceptions that are thrown from an application that runs in a 64-bit version of Windows are ignored) that you will put in your process code:

// my SDK is v6.0A and the two APIs are not available in the .h files, so I need to get them at runtime
#define PROCESS_CALLBACK_FILTER_ENABLED     0x1
typedef BOOL (WINAPI *GETPROCESSUSERMODEEXCEPTIONPOLICY)(__out LPDWORD lpFlags);
typedef BOOL (WINAPI *SETPROCESSUSERMODEEXCEPTIONPOLICY)(__in DWORD dwFlags );
HINSTANCE h = ::LoadLibrary(L"kernel32.dll");
if ( h ) {
   GETPROCESSUSERMODEEXCEPTIONPOLICY GetProcessUserModeExceptionPolicy = reinterpret_cast< GETPROCESSUSERMODEEXCEPTIONPOLICY >( ::GetProcAddress(h, "GetProcessUserModeExceptionPolicy") );
   SETPROCESSUSERMODEEXCEPTIONPOLICY SetProcessUserModeExceptionPolicy = reinterpret_cast< SETPROCESSUSERMODEEXCEPTIONPOLICY >( ::GetProcAddress(h, "SetProcessUserModeExceptionPolicy") );
   if ( GetProcessUserModeExceptionPolicy == 0 || SetProcessUserModeExceptionPolicy == 0 ) {
      return;
   }
   DWORD dwFlags;
   if (GetProcessUserModeExceptionPolicy(&dwFlags)) {
      SetProcessUserModeExceptionPolicy(dwFlags & ~PROCESS_CALLBACK_FILTER_ENABLED); 
   }
}

It may be you have to add also an unhandled exception filter: the filter acts like a "top level exception handler" that is like a topmost catch block. For extracting a programmer-friendly string from _EXCEPTION_POINTERS you can see Is there a function to convert EXCEPTION_POINTERS struct to a string?

LONG WINAPI my_filter(_In_  struct _EXCEPTION_POINTERS *ExceptionInfo)
{
   ::OutputDebugStringA("an exception occured!");
   return EXCEPTION_EXECUTE_HANDLER;
}

You add the filter with:

::SetUnhandledExceptionFilter(my_filter);

and you have to do it in every threads of your process: while the previous snippet is per-process, the filter is per-thread.