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From: cjrgreen@concentric.net (Christopher Green)
Subject: Re: Alternate to Unchecked_Conversion - Portable?
Date: 1999/02/23
Message-ID: <36d3bf1f.1891152@nntp.concentric.net>#1/1
X-Deja-AN: 447795475
References: <36d05e39.0@news.pacifier.com>
 <36d2638e.6427631@nntp.concentric.net> <7avpi0$jke$1@nnrp1.dejanews.com>
Organization: Concentric Internet Services
Newsgroups: comp.lang.ada
Date: 1999-02-23T00:00:00+00:00
List-Id: <comp.lang.ada>

On Wed, 24 Feb 1999 02:52:52 GMT, robert_dewar@my-dejanews.com wrote:

>In article <36d2638e.6427631@nntp.concentric.net>,
>  cjrgreen@concentric.net (Christopher Green) wrote:
>> It is primarily useful in situations in which alternative
>> implementations end up causing a bitwise copy.  If
>> the object to be converted is large, or the conversion
>> must be done many times, this can be a win.
>
>This seems bogus to me. If you replace this by unchecked
>conversion of *pointers* (i.e. access values), NOT the
>items themselves, then there is no bit copying, and no
>inefficiency at all in the access.
>
>-----------== Posted via Deja News, The Discussion Network ==----------
>http://www.dejanews.com/       Search, Read, Discuss, or Start Your Own    

Unchecked conversion of C pointers to Ada access values
is, in my experience, no more portable than using address
clauses to alias structured types.  When the desired Ada
object is an instance of an unconstrained type, converting
a pointer is completely nonportable and usually impractical.

-- 
Chris Green
Advanced Technology Center
Laguna Hills, California