Weird Exception Problem

[dog.ee.lbl.gov!hellgate.utah.edu!cascades.utah.edu!matwood@ucbvax.Berkele y.EDU (Mark Atwood)]

I am still learning Ada (the hard way) and have encountered a weird problem.
I don't know if its a compiler problem or if It's Supposed To Do That".

We have a moderatly large (14 KLOC) Ada program on an HP controller
(pretty much a HP9000/300 type thing) and we're using Alsys Ada 5.5.0.
I seems to be impossible to talk to a real live non-saleperson there.
We're controlling a piece of equipment via an HPIB IEEE-488 bus.  If
the equipment or the HPIB cable goes down, we have set it up to raise
a TEXT_IO.DEVICE_ERROR.  This works great, most of the time.

In one package, if an exception is raised, we get a PROGRAM_ERROR with
no hints.  No stack trace, no exec history, no line numbers, no reason
given, and whats worse -- we cannot trap it in a handler.  I've
intentintionally caused exceptions in this part of the code, and got
the same behavior.  This code isnt any different in any way that I
can tell from other parts of this program, where the exception
handling works great.

I tried reading the LRM and it doesnt help much.  It says that a
PROGRAM_ERROR can be raised if I try using something before its been
"elaborated".  I guess its a good yardstick of the depth of my Ada
understanding that I still dont know what "elaboration" really is, even
after reading the LRM.

Also, if an exception is raised in a "library unit" the program will
abort.  Once again, I couldn't figure out what a "library unit" is.

All this stuff seems to be in LRM section 10.


Can anyone help me out?


---
Mark Atwood               :: DOD-STD-2167A and DOD-STD-1815A
matwood@peruvian.utah.edu :: All who understand, I smile with you.
The University has enough problems without being blamed for mine.