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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Floating point problem
Date: 1997/04/02
Message-ID: <dewar.859986420@merv>#1/1
X-Deja-AN: 230129791
References: <199703271518_MC2-1360-15BE@compuserve.com> <dewar.859526944@merv>
 <1997Mar28.095005.1@eisner> <dewar.859583580@merv> <333E18D8.1F84@bix.com>
 <1997Mar30.113716.1@eisner> <dewar.859869032@merv> <1997Apr1.151216.1@eisner>
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-04-02T00:00:00+00:00
List-Id: <comp.lang.ada>


<<If there is an operating system which will start up the program on
the "wrong" chip, yes.>>

There are operating systems for some machines that will attempt to start
up arbitrary binary files. So by your peculiar reasoning:

(a) All compiler writers for all machines must know about that case
(b) They must put in defences against the program starting up in this case

dubious I think ....

I agree that it would be nice if there were a check for no fpt processor.
But it is of an importance level such that there are so many things ahead
of it that unless someone is more interested in doing the work than
complaining, it probably will never happen!

Actually there is also the point that putting in such a check would reduce
current functionality, since right now you CAN run GNAT on a machine with
no fpt, if you stay away from real arithmetic.

You can use pragma Restrictions (No_Floating_Point) in Ada 95 (it is an
annex H feature, of course implemented in GNAT, since we implement all
annexes):

     1. pragma Restrictions (No_Floating_Point);
     2. procedure q is
     3.    g : float;
               |
        >>> violation of restriction "no_floating_point"

     4. begin
     5.    g := 1.0;
           1    2
        >>> violation of restriction "no_floating_point"
        >>> violation of restriction "no_floating_point"

     6. end q;


So in fact you can use GNAT now on such a machine, with the compiler
checking for violations of the restriction.

The nice feature would be to condition the dynamic check on the presence
of floating-point in the program, but that's even more work, and even
less likely to get done.