From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on ip-172-31-74-118.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.5-pre1 Date: 11 Sep 91 19:03:25 GMT From: aio!sweetpea.jsc.nasa.gov!yow@eos.arc.nasa.gov (Bill Yow) Subject: Risk of using Ada for RISK Message-ID: <1991Sep11.190325.12568@aio.jsc.nasa.gov> List-Id: This was posted to RISKS DIGEST 12.29. Since it has several Ada comments/quest ions I have re-posted it here. ----------------------------- 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!