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From: Jacob Sparre Andersen <jacob@jacob-sparre.dk>
Newsgroups: comp.lang.ada
Subject: Bug in 'gnatmake' (Was: Range check for type 'Integer')
Date: Mon, 17 Jun 2013 15:23:11 +0200
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2013-06-17T15:23:11+02:00
List-Id: <comp.lang.ada>

Peter Brooks wrote:

> This is   134217728
> This is   268435456
> This is   536870912
> This is  1073741824
> This is -2147483648
> This is           0
> This is           0
> This is           0
> This is           0
> This is           0
> This is           0
> This is           0
> This is           0
> ..... [forever]
>
> So the 'Integer' has rolled over to negative and then rolled back to 0
> - but with no run-time error.
>
> Why is there no range check error on type Integer?

Because there is a major error in the design of GNAT.  You have to give
'gnatmake' a very specific set of command line flags to turn it into an
Ada compiler:

   -fstack-check --  Generate stack checking code
   -gnata        --  Enable assertions
   -gnatE        --  Dynamic elaboration checking
   -gnato        --  Overflow checking

If you use the GNAT Project Manager (and '*.gpr' files), I suggest that
you copy this file project file and use it in all you (GNAT based) Ada
projects:

   http://repositories.jacob-sparre.dk/ada-user-journal-tools/src/40323d1c952e20020bd056f2df698d252c4cd87f/ada_2012.gpr?at=default

Here is a simple example of how to use the file:

   http://repositories.jacob-sparre.dk/ada-user-journal-tools/src/40323d1c952e20020bd056f2df698d252c4cd87f/auj_tools.gpr?at=default

The more complicated version has something like:

   package Compiler is
      for Default_Switches ("Ada")
        use Ada_2012.Compiler'Default_Switches ("Ada") &
            ("-some-extra-switches");
   end Compiler;

instead of:

   package Compiler renames Ada_2012.Compiler;

Greetings,

Jacob
-- 
"Never interrupt your enemy when he is making a mistake."