Re: Ada Core Technologies and Ada95 Standards

[dewar@cs.nyu.edu (Robert Dewar)]

Michael said

"Ken was wrong when he said "majority". He should have said "vast
majority". But if you want specific numbers, lets say that 97% of
our tests to demonstrate compiler errors are both small and non-
proprietary. (I give myself a 2% margin of error for this estimate).
And while I'm at it, I should also define "small". Our small examples
are generally between 5 and 300 lines of Ada code. And most (lets
say 70%) of these are less than 50 lines."

OK, well that *is* interesting. What that says is that the F22 code
may not be entirely typical code. Actually I hope that is the case.
A lot of the Ada 95 code we use seems extraordiarily comlex, almost
as if every possible feature and every possible interaction was
deliberately being introduced. I would not at all be surprised to
find that the F22 takes a more conservative approach (as does GNAT
itself, the GNAT compiler itself very rarely runs into compiler
problems -- that's partly because it is its own best regression
test, but also because we are very conservative in the use of
fancy features in the compiler itself).

What we found with Ada 83 was that what was least well tested in the
ACVC suite was complex interactions between features.

It is true that many of the problems in GNAT can be reduced to simple
test programs, but there are also many examples that show up only
in large cases. I will give just one example of this. The Irix
implemntation does not handle jumps of more than 128K bytes nicely.
It takes a failry big progrm to show up this bug! Big enough in fact
that no C program had ever run into it, but sure enough one big project
had some VERY large Ada procedures that did bump into this limit.