Is this a GNAT bug???

[robert_s_quinn@yahoo.com (Robert Quinn)]

I originally posted a question regarding pragma pack, but after
stripping away all the details I found what may be a bug, or just
something I don't understand about low level programming.  I will post
it, and it is brief code, but in a nutshell an array of 64 bits packs
fine, but an array of 65 bits does not!

I will post code here that is actually compilable, unlike my last
message :)

I am using gnat3.13p on Sparc Solaris

Here is the WORKING, NO ERRORS code:

package test is
   type ONE_BIT_TYPE is range 0..1;
   for ONE_BIT_TYPE'SIZE use 1;

   type ARRAY_OF_64_BITS_TYPE is array (1..64) of ONE_BIT_TYPE;
   pragma pack (ARRAY_OF_BITS_TYPE);

   type MY_TYPE is record
      ARRAY_OF_64_BITS : ARRAY_OF_64_BITS_TYPE;
   end record;

   pragma pack (MY_TYPE);

   for MY_TYPE use record
      ARRAY_OF_64_BITS at 0 range 0..63;
   end record;

end test;

** NOW just replace 64 with 65 (and 63 with 64 on range) and Voila',
you get the error:
  "size of ARRAY_OF_65_BITS too small, minimum allowed is 72"

Here is the OFFENDING code:

package test is
   type ONE_BIT_TYPE is range 0..1;
   for ONE_BIT_TYPE'SIZE use 1;

   type ARRAY_OF_65_BITS_TYPE is array (1..65) of ONE_BIT_TYPE;
   pragma pack (ARRAY_OF_BITS_TYPE);

   type MY_TYPE is record
      ARRAY_OF_65_BITS : ARRAY_OF_65_BITS_TYPE;
   end record;

   pragma pack (MY_TYPE);

   for MY_TYPE use record
      ARRAY_OF_65_BITS at 0 range 0..64;
   end record;

end test;


So why can't I pack a bit array of 65 bits or more bits? Anyone have
any comments?