Question

I want to program a daemon-manager that takes care that all daemons are running, like so (simplified pseudocode):

void watchMe(filename)
{
    while (true)
    {
        system(filename); //freezes as long as filename runs
        //oh, filename must be crashed. Nevermind, will be restarted            
    }
}       

int main()
{
    _beginThread(watchMe, "foo.exe");
    _beginThread(watchMe, "bar.exe");
}

This part is already working – but now I am facing the problem that when an observed application – say foo.exe – crashes, the corresponding system-call freezes until I confirm this beautiful message box:

This makes the daemon useless.

What I think might be a solution is to make the main() of the observed programs (which I control) “uncrashable” so they are shutting down gracefully without showing this ugly message box.

Like so:

try
{
    char *p = NULL;
    *p = 123; //nice null pointer exception
}
catch (...)
{
    cout << "Caught Exception. Terminating gracefully" << endl;
    return 0;
}

But this doesn’t work as it still produces this error message:

(“Untreated exception … Write access violation …”)

I’ve tried SetUnhandledExceptionFilter and all other stuff, but without effect.

Any help would be highly appreciated.

Greets

Answer 1

This seems more like a SEH exception than a C++ exception, and needs to be handled differently, try the following code:

__try
{
    char *p = NULL;
    *p = 123; //nice null pointer exception
}
__except(GetExceptionCode() == EXCEPTION_ACCESS_VIOLATION ? 
             EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH)
{
    cout << "Caught Exception. Terminating gracefully" << endl;
    return 0;
}

But thats a remedy and not a cure, you might have better luck running the processes within a sandbox.