Re: Alternate to Unchecked_Conversion - Portable?

[robert_dewar@my-dejanews.com]

In article <36d65c7c.15971534@nntp.concentric.net>,
  cjrgreen@concentric.net (Christopher Green) wrote:
> Maybe the Unchecked_Conversion of access types has
> wider approval from those who develop language standards.

If you are using a language, it is incumbent on you to KNOW
the language! The language is defined by the standard, not
by the behavior of the compiler you are using.

> But I cannot afford to spend more time than I have to in
> troubleshooting code that fails to port to a new
> compiler.

If you want to minimize time spent porting stuff, then
know the language and AVOID erroneous constructs.

> In the products I deal with regularly, address
> representation clauses are the cause of no more
> portability problems than are uses of
> Unchecked_Conversion.

Yes, but those are, as you say "the products you deal
with regularly". If you use erroneous constructs then
new versions or new compilers may cause problems that
you do not anticipate.

If you use implementation dependent features, you need
to KNOW you are doing it, and know EXACTLY what you are
depending on, and CHECK that the vendor of your current
compiler really does support what you expect, and USE
these criteria for selecting new compilers.

It is amazing to me how many people write implementation
dependent and erroneous code without even knowing they are
doing so. They then get indignant when their code does not
port to a new compiler, new machine, or even new version of
the same compiler they are using.

  "But I thought Ada was portable! Why should I have to
  change my code. My code is correct -- how do I know,
  because it works! [i.e. appears to work]."

The attitude that you do not have time to learn the
language, and that that stuff is all junk that has to
do with "those who develop language standards", and has
nothing to do with you, is what leads some people to have
a lot of trouble porting their code, while other people
have far less trouble!

There is no question that conversion of access types is,
for many technical reasons, safer and more portable than
the use of address overlays. The reasons have been
discussed here many times.

Yes, you can dismiss these discussions as irrelevant
nonsense which you don't have time to follow, but this
may well be a matter of saving a bit of time now, to be
paid back with high interest later on!





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