Question

In an application I’m making, sometimes exceptions that are thrown but unhandled, seem to disappear into thin air and cause strange bugs with the GUI.

I’ll usually find it by stepping through until reaching the line where the exception is thrown, at which point Visual Studio immediately stops stepping and returns to the application.

It’s an IRC app so it’s heavily event-driven by the async socket connection. Not sure if that is relevant.

I don’t have any empty catch blocks anywhere or anything like that.

Answer 1

Apparently this is a known bug with x64 machines.

The bug and a workaround is on Microsoft Connect.

Edit:

If anyone is interested in the cause, this was posted when the bug was closed:

Hello,

This bug was closed as “External” because this behavior results from
how x64 version of Windows handle exceptions. When a user mode
exception crosses a kernel transition, x64 versions of Windows do not
allow the exception to propagate. Therefore attached debuggers are
unaware of the fact that an exception occured resulting in the
debugger failing to break on the unhandled exception.

Unfortunately where is nothing that the Visual Studo team can do to
address this, it is the result of operating system design. All
feedback regarding this issue should be addressed to the Windows team;
however the Windows team considers this to be the “correct” operating
system design, and considers the x86 behavior to be “incorrect”.

Best Regards, Visual Studio Debugger