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From: Martin Krischik <krischik@users.sourceforge.net>
Newsgroups: comp.lang.ada
Subject: Re: Ada Pointer Size Problem
Date: Wed, 13 Oct 2004 10:07:26 +0200
Organization: AdaCL
Message-ID: <219535369.f3yiO4m2UC@linux1.krischik.com>
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Date: 2004-10-13T10:07:26+02:00
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skidmarks wrote:

> Stephen Leake <stephen_leake@acm.org> wrote in message
> news:<mailman.269.1097458704.390.comp.lang.ada@ada-france.org>...
>> aschwarz@acm.org (skidmarks) writes:
> 
>> > I've looked at the 'info' tex file included with the
>> > gcc distribution and so far have not found how to
>> > change a 64-bit pointer to a 32-bit pointer.
>> 
>> Why do you want to do that? A pointer to an integer is not a pointer
>> to a string.
> 
>   I misspoke, perhaps sarcastically. I don't want to change pointer sizes
>   and you have gone far to explain what I'm seeing. Although the reason
>   for including the dope vector as part of an Access Type eludes me, the
>   explanation I understand. (The elusion is because it seems just as
>   reasonable to 'point' to a dope vector when specifying an access type
>   rather than including the dope vector as the Access Type.) Albeit,
>   thanks to all for the clarification between System.Address and Access
>   Type.

Actually the compiler vendors are free to choose the implementation thats
suits them best.

>> > I've thought that maybe I am getting the dope vector size associated
>> > with the String_Ptr but this really doesn't make sense.
>> 
> 
>   See above. To resolve this (type of) difficulty locally - for Ada83
>   interfaces to C primarily, we do the following:
> 
>    A_Access   := array'Access
>    B_Pointer  := array(array'First)'Address
> 
>   and for the purists, THIS IS NOT TRUE ADA, so don't flame me because
>   it's not true Ada.

I use this trick as well from time to time in Ada 95. It's faster and saves
memory. 

Even cooler:

type Ada_String is String (1.. C_String_Len);
for Ada_String'Address use C_String'Address;

With Regads

Martin
-- 
mailto://krischik@users.sourceforge.net
http://www.ada.krischik.com