(Marc H. Donner and David H. Jameson, "Language and Operating System Features for Real-time Programming", Computing Systems vol 1 number 1, winter 1988, pp 33-62):
> Ill-chosen abstraction is particularly evident in the design of the Ada runtime system. The interface to the Ada runtime system is so opaque that it is impossible to model or predict its performance, making it effectively useless for real-time systems.
> Am I correct in thinking that several (two?) missiles were recently destroyed on launch each of which had their guidance systems coded in Ada? Were the problems which forced the destruction of the missiles the result of bad software design or some inherent ambiguity in Ada syntax?
> I spotted but unfortunately left unlogged a report somewhere which gave an account of a talk by a leading scientist (name?) in the military technology area who expressed grave reservations about the design of Ada. I think the report mentioned that the person expressed little confidence in guidance systems coded in Ada.
In light of decades of demonstrated reliability of Ada use in aerospace applications, a bunch of comments about Ada from the late 1980s are meaningless.
The quoted comment is saying that the Ada support runtime is so high level that it sometimes ends up being unsuitable for real-time programming. This is exactly the kind of concern that would be hard to improve even in recent versions of Ada, whereas it is naturally addressed by Rust.
That's one of those times when looking around at what exists and not only old papers might help. Been doing soft and hard real-time on baremetal (no OS) with Ada tech for a long time. There's a whole of language constructions to help reducing the language set for hard embedded stuff (no dynamic allocation, no specific constructs, no secondary stack,...) and there are the Ravenscar and Jorvik profiles.
Very strange to hear/read about non implementability of hard real-time with Ada when one the guy I hired years ago was one of the OS-for-aircraft-embedded-computer, doing that since the 90s...
How do you figure Rust handles this better than Ada? Ada's runtime has always been configurable. You can customise the runtime library fairly easily to strip out things that don't suit your target platform. Most compilers even ship with a 'Zero Footprint (zfp)' runtime which is designed for minimal overhead.
You could make the exact same argument about C if you wanted. C's standard library, as implemented for most operating systems, is poorly suited for real-time systems too. That's why it's modified to be fit for purpose when targeting them.
Whether people know it or not, they've been living in the Ada world for a long time. A good deal of the world's critical real-time systems have been running on Ada for decades. Flight, and fire control systems in aircraft, Many major ATC systems, etc. The list goes on, and on.
> After a number of top-secret meetings at the highest levels, the "Ada Project" was conceived. ... Its goal was to divert Soviet attention from truly productive computer languages like Lisp, and convince them that only a bloated, grossly inefficient, high order compiled language along the lines of PL/I could be reasonably utilized in the deployment of military embedded systems. The use of a standardized, inefficient language would provide a one-two punch: it would render super-programmers useless, and it would increase the demands on hardware by more than two orders of magnitude.
> The Ada Project was inspired by the unexpected success of the IBM System/360 architecture behind the Iron Curtain. The Ada Project's wizards {the Ada Project was conceived at Kirtland AFB, NM, near Roswell} reasoned that if the Soviets could be lured into copying the 360 architecture, they could also be lured into copying the Ada language, and if this language were fiendishly designed to make real-time systems essentially impossible to program, then the Soviet military machine would grind to a halt.
> Although Ada would also severely impact American software productivity, it was felt that--just as cancer-fighting chemotherapy nearly kills healthy tissue while it kills tumors--the healthier US economy would be better able to bear the severe burden of an unproductive software industry than the Soviet economy could. Thus, while American geeks were inferior to Soviet geeks, our Elbonian hordes could beat their Mongolian hordes.
Presumably modern Ada is better! Even the sarcastic paper hints at it:
> Now that the Wicked Witch of the East is dead, the wizards have finally allowed Ada to evolve into Ada9X, which fixed some of Ada's more egregious dysfunctions. However, even today the brilliance of Ada's original conception still shines brightly through.
> "The interface to the Ada runtime system is so opaque that it is impossible to model or predict its performance, making it effectively useless for real-time systems."
This comment didn't age well. If you've ever been a passenger on a modern jetliner you've most likely trusted your life to real-time systems coded in Ada.
> "Am I correct..."
> "Were the problems..."
> "...by a leading scientist (name?)..."
> "I think the report..."
Terrible. Entirely conjecture. Not one concrete source to substantiate these claims.
(Marc H. Donner and David H. Jameson, "Language and Operating System Features for Real-time Programming", Computing Systems vol 1 number 1, winter 1988, pp 33-62):
> Ill-chosen abstraction is particularly evident in the design of the Ada runtime system. The interface to the Ada runtime system is so opaque that it is impossible to model or predict its performance, making it effectively useless for real-time systems.
More:
https://catless.ncl.ac.uk/Risks/6/36#subj12
> Am I correct in thinking that several (two?) missiles were recently destroyed on launch each of which had their guidance systems coded in Ada? Were the problems which forced the destruction of the missiles the result of bad software design or some inherent ambiguity in Ada syntax?
> I spotted but unfortunately left unlogged a report somewhere which gave an account of a talk by a leading scientist (name?) in the military technology area who expressed grave reservations about the design of Ada. I think the report mentioned that the person expressed little confidence in guidance systems coded in Ada.