Question

I’ve got a c++ app that wraps large parts of code in try blocks. When I catch exceptions I can return the user to a stable state, which is nice. But I’m not longer receiving crash dumps. I’d really like to figure out where in the code the exception is taking place, so I can log it and fix it.

Being able to get a dump without halting the application would be ideal, but I’m not sure that’s possible.

Is there some way I can figure out where the exception was thrown from within the catch block? If it’s useful, I’m using native msvc++ on windows xp and higher. My plan is to simply log the crashes to a file on the various users’ machines, and then upload the crashlogs once they get to a certain size.

Answer 1

This is possible with using SEH (structured exception handling). The point is that MSVC implements C++ exceptions via SEH. On the other hand the pure SEH is much more powerful and flexible.

That’s what you should do. Instead of using pure C++ try/catch blocks like this:

try
{
    DoSomething();
} catch(MyExc& exc)
{
    // process the exception
}

You should wrap the inner code block DoSomething with the SEH block:

void DoSomething()
{
    __try {
        DoSomethingInner();
    }
    __except (DumpExc(GetExceptionInformation()), EXCEPTION_CONTINUE_SEARCH) {
        // never get there
    }
}

void DumpEx(EXCEPTION_POINTERS* pExc)
{
    // Call MiniDumpWriteDump to produce the needed dump file
}

That is, inside the C++ try/catch block we place another raw SEH block, which only dumps all the exceptions without catching them.

See here for an example of using MiniDumpWriteDump.