Re: Memory limits in Ada where Fortran has none

["Dr. Adrian Wrigley" <amtw@linuxchip.demon.co.uk.uk.uk>]

On Sun, 06 Mar 2005 19:05:21 -0500, Robert A Duff wrote:

> The following works for me:
> 
> package Test_Pkg is
>     X: array (1..400_000_000) of Integer := (others => 999);
> end Test_Pkg;
> 
> with Test_Pkg; use Test_Pkg;
> with Text_IO; use Text_IO;
> procedure Test is
> begin
>     Put_Line(Integer'Image(X(X'Last)));
> end Test;

I am very wary of a test like this because GNAT sometimes
silently accesses the wrong element of very large data, if I
remember correctly. A correctly written program can (and did!)
thus fail catastrophically.  Large records in particular are
suspect (on GNAT 3.15p, x86). (I have no test case to hand
at the moment).  I don't know if it is affected by -gnato
and default absence of overflow checking.

A more comforting test would place a *different* value at
each location, and check they are all correct!
-- 
Dr. Adrian Wrigley, Cambridge, UK.