From: "Doobs" <doobs@doobs.com>
Subject: Any way of persuading GNAT/GCC to implement a true overlay and not a pointer?
Date: Sat, 1 Apr 2006 14:47:59 +0100
Date: 2006-04-01T14:47:59+01:00 [thread overview]
Message-ID: <LIednWDbPNgXGbPZRVnysQ@pipex.net> (raw)
I was under the impression that code of the following form :
X : <Some Type>;
Y : <Some Type>;
for Y'Address use X'Address;
would result in an overlay in the resulting code. However on a project
where external test equipment showed that the contents of X were NOT the
same as Y I investigated further. I checked on both a Windows host version
of GCC (3.4.2) and a target cross compiler (GCC 3.4.4) and on both the
construct above is actually implemented using indirection (a pointer). The
map file and symbol table show that irrespective of the data type and size
of Y it is always implemented as a pointer to X. Although this appears
semantially identical to an overlay as far as the progam is concerned it is
NOT identical as far as an external observer is concerned. I have a bit
packed record which I wanted to return as an array of longwords to pretty
dumb test equipment. The easiest way *would* be to overlay a longword
array - however this would not appear to be possible.....
next reply other threads:[~2006-04-01 13:47 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-01 13:47 Doobs [this message]
2006-04-01 14:33 ` Any way of persuading GNAT/GCC to implement a true overlay and not a pointer? Jeffrey Creem
2006-04-01 16:52 ` Doobs
2006-04-01 17:56 ` Martin Krischik
2006-04-01 18:04 ` Dmitry A. Kazakov
2006-04-01 17:08 ` Florian Weimer
2006-04-01 17:54 ` Doobs
2006-04-01 18:19 ` Doobs
2006-04-01 20:01 ` Jeffrey Creem
2006-04-01 21:33 ` Doobs
2006-04-03 12:25 ` Gerd
2006-04-01 20:57 ` Dmitry A. Kazakov
2006-04-04 1:23 ` Randy Brukardt
2006-04-10 1:42 ` Justin Gombos
2006-04-10 20:12 ` Randy Brukardt
2006-04-11 13:54 ` Making money on open source, if not by selling _support_, then how? Marc A. Criley
2006-04-11 15:13 ` Justin Gombos
2006-04-11 16:22 ` Dmitry A. Kazakov
2006-04-11 17:56 ` Justin Gombos
2006-04-11 18:38 ` Georg Bauhaus
2006-04-12 13:59 ` Justin Gombos
2006-04-12 14:39 ` Georg Bauhaus
2006-04-15 19:33 ` Justin Gombos
2006-04-12 17:07 ` Larry Kilgallen
2006-04-13 3:16 ` Justin Gombos
2006-04-11 19:59 ` Randy Brukardt
2006-04-11 20:18 ` Ed Falis
2006-04-12 14:10 ` Justin Gombos
2006-04-12 20:57 ` Randy Brukardt
2006-04-15 20:37 ` Justin Gombos
2006-04-18 0:24 ` Randy Brukardt
2006-04-18 16:02 ` Justin Gombos
2006-04-12 19:27 ` Martin Dowie
2006-04-12 8:32 ` Dmitry A. Kazakov
2006-04-12 11:23 ` Georg Bauhaus
2006-04-12 15:34 ` Dmitry A. Kazakov
2006-04-12 17:11 ` Georg Bauhaus
2006-04-12 19:37 ` Dmitry A. Kazakov
2006-04-12 21:56 ` Georg Bauhaus
2006-04-13 9:17 ` Dmitry A. Kazakov
2006-04-13 14:18 ` Georg Bauhaus
2006-04-14 10:01 ` Dmitry A. Kazakov
2006-04-14 12:55 ` Georg Bauhaus
2006-04-15 10:13 ` Dmitry A. Kazakov
2006-04-15 18:07 ` Georg Bauhaus
2006-04-13 2:58 ` Justin Gombos
2006-04-13 9:17 ` Dmitry A. Kazakov
2006-04-15 21:17 ` Justin Gombos
2006-04-16 10:53 ` Dmitry A. Kazakov
2006-04-16 13:03 ` Georg Bauhaus
2006-04-16 17:59 ` Dmitry A. Kazakov
2006-04-16 20:53 ` Georg Bauhaus
2006-04-17 9:16 ` Dmitry A. Kazakov
2006-04-19 20:38 ` Justin Gombos
2006-04-20 18:01 ` Dmitry A. Kazakov
2006-04-18 0:29 ` Randy Brukardt
2006-04-16 14:55 ` Justin Gombos
2006-04-16 17:59 ` Dmitry A. Kazakov
2006-04-19 18:17 ` Justin Gombos
2006-04-20 18:07 ` Dmitry A. Kazakov
2006-04-11 15:34 ` Justin Gombos
2006-04-12 2:59 ` Steve
2006-04-13 7:41 ` Jean-Pierre Rosen
2006-04-13 13:18 ` Marc A. Criley
2006-04-13 13:35 ` Dmitry A. Kazakov
2006-04-13 13:57 ` Making money on open source, if not by selling _support_, then Larry Kilgallen
2006-04-13 19:37 ` Justin Gombos
2006-04-13 21:02 ` Larry Kilgallen
2006-04-14 2:49 ` Justin Gombos
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