OpenEuphoria

Re: Robert Craig... One Wish Please

• Posted by Robert Craig <rds at RapidEuphoria.com> Jul 30, 2002
• 403 views

Jordah Ferguson writes:
> I have only one wish i would like added to exw. The ability to call a
> routine at crash time ...

A global exception handler has been on my list for a long time,
at least in principle. It wouldn't be hard to implement,
but it raises some issues that have to be examined carefully,
for example:

   - It would be almost useless in code translated to C, since
     there are very few run-time error checks. It would increase the
     chances that a program could not be translated properly.

   - It might make certain optimizations more difficult, since
     you couldn't be sure at compile-time that a series of
     statements would always be executed in a predictable order.
     If I wanted to free the value of a global variable early, that might
     be a mistake, since an exception might happen, causing
     a sudden jump to a routine that uses that variable, etc.

   - People might start to "abuse" the feature, using it for normal
     processing, not just exceptions, especially when some clever
     person reports how he speeded up his loop by 5%, by removing his
     test for an out-of-bounds subscript, and relying instead on the
     exception handler.

   - It might preclude doing an eventual full treatment of
     exceptions like C++ and other languages, where
     each block of statements can have its own handler.

   - There are issues, such as: Do we allow the exception handler to return?
     Do we provide the exception handler with a standardized error code
     so it will know what happened? etc.

   - If you are mainly interested in freeing resources,
     you should know that Euphoria flushes your files and closes them,
     frees .dll's, and all the memory that you allocated
     via allocate() is freed as well.

   - If you mainly just want to apologize to your user and explain
     what to do, you can do that with crash_message().

I had an example a while back where I might have benefited from this.
I had a FreeBSD Euphoria background process running
24 hours a day and I thought it would be very useful if
it could send me an email if a Euphoria exception occurred.
Eventually I made it a "cron" job, started hourly, and I found
that cron itself sends me an e-mail if any error messages
occur when running a program. So the problem was solved.

Regards,
   Rob Craig
   Rapid Deployment Software
   http://www.RapidEuphoria.com