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I recently started re-reading "Programming in Ada" by J.G.P. Barnes about the original Ada. In my opinion, it was not that good of a language. Plenty of ways to

by phicoh 2y ago

I recently started re-reading "Programming in Ada" by J.G.P. Barnes about the original Ada. In my opinion, it was not that good of a language. Plenty of ways to trigger undefined behavior. Where C was clearly designed to be a practical language with feedback from implementing an operating system in C. Ada lacked that kind of practical experience. And it shows. I don't know anything about modern day Ada, but I can see why it didn't catch on in the Unix world.

pyjarrett 2y ago
> Plenty of ways to trigger undefined behavior I'm curious about this list, because it definitely doesn't seem that way these days. It'd be interesting to see how many of these are still possible now.
- kqr 2y ago
  Search engines seem to no longer produce an estimate of the hit count, but here are some of the ways: https://duckduckgo.com/?t=h_&q=site%3Aada-auth.org+%22erroneous%22&ia=web https://duckduckgo.com/?t=h_&q=site%3Aada-auth.org+%22errone...
- phicoh 2y ago
  I didn't make a list, but let me give an example. Page 22 where variable declarations are introduced: If a variable is declared and not given an initial value then great care must be taken not to use the undefined value of the variable until one has been properly given to it. If a program does use the undefined value in an uninitialised variable, its behaviour will be unpredictable; the program is said to be erronous.
micronian2 2y ago
I recall watching a presentation about C++20. During the presentation, the presenter said there were about 163 undefined behaviors in the C language (note: I think it was C99) which implied there were many more in C++ since it’s a much more complex language. Unfortunately, I don’t have a link to that presentation. You might have heard about the SPARK variant of Ada. I recall reading in an article many years ago that the original version of SPARK was based on Ada83 because it is a very safe language with a lot less undefined behaviors, which is key to trying to statically prove the correctness of a program.

by phicoh 2y ago

pyjarrett 2y ago

> Plenty of ways to trigger undefined behavior I'm curious about this list, because it definitely doesn't seem that way these days. It'd be interesting to see how many of these are still possible now.

kqr 2y ago
Search engines seem to no longer produce an estimate of the hit count, but here are some of the ways: https://duckduckgo.com/?t=h_&q=site%3Aada-auth.org+%22erroneous%22&ia=web https://duckduckgo.com/?t=h_&q=site%3Aada-auth.org+%22errone...
phicoh 2y ago
I didn't make a list, but let me give an example. Page 22 where variable declarations are introduced: If a variable is declared and not given an initial value then great care must be taken not to use the undefined value of the variable until one has been properly given to it. If a program does use the undefined value in an uninitialised variable, its behaviour will be unpredictable; the program is said to be erronous.

micronian2 2y ago

I recall watching a presentation about C++20. During the presentation, the presenter said there were about 163 undefined behaviors in the C language (note: I think it was C99) which implied there were many more in C++ since it’s a much more complex language. Unfortunately, I don’t have a link to that presentation. You might have heard about the SPARK variant of Ada. I recall reading in an article many years ago that the original version of SPARK was based on Ada83 because it is a very safe language with a lot less undefined behaviors, which is key to trying to statically prove the correctness of a program.