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Date: Fri, 18 Nov 1994 16:27:49 +0100
Sender: Ada programming language <INFO-ADA@NDSUVM1.BITNET>
From: Bob Wells #402 <wel@EUROCONTROL.DE>
Subject: Range Check Query
Comments: To: INFO-ADA%NDSUVM1.BITNET@vm.gmd.de
Date: 1994-11-18T16:27:49+01:00
List-Id: <comp.lang.ada>

G'day everyone,
Hope you're all having a lovely Friday!

Why does the following not raise a Constraint_Error exception?
(It doesn't even raise a compile time warning)

  type dn18906 is  -- layout is for the 18906 message  .
    record
      dnspare  : integer range 0 .. 1;
      dnspare2 : integer range 0 .. 3;
      dnch1    : integer range 0 .. (2**7) - 1;
      dnch2    : integer range 0 .. (2**7) - 1;
    end record;

   for dn18906 use
     record at mod 1;
       dnspare at 0 range 0 .. 1;
       dnspare2 at 0 range 2 .. 7;
       dnch1 at 0 range 8 .. 15;
       dnch2 at 0 range 16 .. 23;
     end record;

   for dn18906'size use 24;

   type Dn_189_Data is array(1 .. N_Data) of Dn18906;
   pragma Pack(Dn_189_Data);

   M_T : Dn_189_Data;
   for M_T use at P_Mesg_Conv(P_Ohead) + 12;

P_Mesg_Conv is an Unchecked_Conversion of an access type to a
system address. The access type points to an incoming byte
stream.

As Bart Simpson says "I didn't do it, I didn't do it!" That is,
I've been "lucky" enough to inherit this code.


OK, then in the body of this package we have:


   if M_T(1).Dnspare = 2 then

--     do something

   end if;

The incoming stream definitely has value of 2 occaisionaly in this
component yet it doesn't raise Constraint_Error?

Once again we are using the

Verdix Ada Compiler, Copyright 1984, 1992
VADSworks for Sun-4 -> MC68020/30/vxWorks, (VADS 6.0.5)
Mon Aug 17 09:11:00 EST 1992 2.0.3(b)

Any help would be greatly appreciated. Thanks and 'avagoodweegend!

@                   --------
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  Bob Wells                      "There are more things in heaven and earth
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