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Editorial Team
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Asked: 2026-05-15T17:36:41+00:00

The following code will give a hard fail when run under Windows 7 32bit:

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The following code will give a hard fail when run under Windows 7 32bit:

void CTestView::OnDraw(CDC* /*pDC*/)
{
    *(int*)0 = 0; // Crash

    CTestDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    if (!pDoc)
        return;

    // TODO: add draw code for native data here
}

However, if I try this on Windows 7 64bit, I just get this in the output window:

First-chance exception at 0x13929384
in Test.exe: 0xC0000005: Access
violation writing location 0x00000000.
First-chance exception at 0x77c6ee42
in Test.exe: 0xC0150010: The
activation context being deactivated
is not active for the current thread
of execution.

What is the reason for this? I know it’s a hardware exception (http://msdn.microsoft.com/en-us/library/aa363082.aspx), but why the difference when ran under 32bit and 64bit? And what can I do to correctly handle these kind of errors? Because they should really be trapped and fixed, as opposed to what currently happens which is Windows just carries on pumping messages to the application and let’s it run (so the user and the developers are completely unaware any problems have actually occurred).

Update:
Our regular crash reporting software uses SetUnhandledExceptionFilter but that doesn’t get called on x64 for hardware exceptions inside a WndProc. Does anyone have any information on this, or a workaround?

Update2:
I’ve reported the issue at Microsoft Connect:
https://connect.microsoft.com/VisualStudio/feedback/details/550944/hardware-exceptions-on-x64-machines-are-silently-caught-in-wndproc-messages

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1 Answer

  1. Editorial Team

    OK, I’ve received a reply from Microsoft:

    Hello,

    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.

    @Skute: note that the Program
    Compatibility Assistant will ask once
    if the program should be allowed to
    continue to execute, and after that it
    will always be allowed, so that may be
    the cause of the confusing behavior
    you are seeing.

    Pat Brenner Visual C++ Libraries
    Development

    So the workaround is either make sure the hotfix is installed, or wrap each WndProc in your application with a __try / __except block.

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