Risk of using Ada for RISK

Risk of using Ada for RISK

[Bill Yow]

This was posted to RISKS DIGEST 12.29.  Since it has several Ada comments/quest
ions I have re-posted it here.

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Date: 9 Sep 91 12:30:01 GMT
From: trwacs!erwin@uunet.uu.net (Harry Erwin)
Subject: Risks of Incompatibilities

I'm interested in identified incompatibilities between the various US
Government standards, beginning with

  POSIX
  GOSIP
  Ada
  B2 Security
  (etc.)

in various applications.  I know of one between UNIX-based POSIX
implementations and Ada tasking that makes the combination inappropriate in
safety-critical real-time and near-real-time applications, and I'm interested
in identifying any others that are known for specific applications.

  [NOTE ADDED LATER IN REPONSE TO A QUERY FROM PGN:]

There is a real issue. Ada running over UNIX can't handle data enablements of
tasks reliably--the problem being that you don't have access to a test-and-set
instruction and you can be interrupted in the middle by the arrival of data
from outside.  The result is spurious enablements and the loss of other
enablements.  That can be disastrous in a safety- or nuclear- critical system.
How many nuclear-capable systems have been written using Ada tasking over UNIX?
How many other problems have been created by incompatible standards? If you
want a background brief, call me at (W)703.734.6092 or (H)703.758.9660.

Harry Erwin   Internet: erwin@trwacs.fp.trw.com

--------------------------

						Later,
						Bill Yow
						(713) 283-4051
						yow@sweetpea.jsc.nasa.gov
						byow@mcimail.com

My opinions are my own!