Re: Ada for C30

[kilgallen@eisner.decus.org (Larry Kilgallen, LJK Software)]

In article <3io711$hs5@bighorn.accessnv.com>, jfj (John Fountain, Jr.) writes:
> gentle@cnj.digex.net (Gentle) wrote>

> writing phase at all.  This should prove to be interesting.
> Overall, my intuition tells me if I could do it in C I can
> do it in Tartan Ada with a little careful construction.
> Probably the biggest hurdle is that C's memory allocation
> are very easy to predict, while in Ada we are not always
> sure of what the compiler will construct and where things
> will be allocated from.

There have always been problems with people writing a Fortran
program in some other language, such that no matter what language
they use it comes out looking like Fortran.

If you need to know how C or Ada is going to allocate the memory,
and depend on undocumented (and therefore non-guaranteed) compiler
behavior, you may be in for a rude awakening with the next version
of any language compiler from any vendor.

If you require a particular memory layout, you should depend on
documented features of the language.  In Ada the Representation
Clauses are the major mechanism for accomplishing this. In some
cases Address Clauses may also be relevant.

Whatever your language, you should rely on documented (and therefore
guaranteed) compiler features to produce particular memory usage.

Larry Kilgallen
whose representation clauses
"just worked" when DEC released Alpha AXP :-)