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From: okellogg <okellogg@freenet.de>
Newsgroups: comp.lang.ada
Subject: pragma Pack vs. Convention C, portability issue?
Date: Wed, 9 Jan 2008 00:40:50 -0800 (PST)
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-- File: main.adb
-- Can we portably rely on pragma Pack taking precedence
-- over Convention C?
with Text_IO;

procedure Main is

   type C_Represented_Enum is (Zero, One, Two, Three);
   pragma Convention (C, C_Represented_Enum);
   -- This would be 32 bits on a 32 bit architecture

   type Perhaps_Packed is array (1 .. 4) of C_Represented_Enum;
   pragma Pack (Perhaps_Packed);
   -- This could be either 8 bits if the compiler lets pragma Pack
   -- take precedence over Convention C, or 4 * 32 = 128 bits
   -- otherwise.

begin
   Text_IO.Put_Line
     ("Perhaps_Packed'Size is" &
      Natural'Image (Perhaps_Packed'Size));
end Main;