From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM autolearn=unavailable autolearn_force=no version=3.4.4 X-Received: by 10.13.213.215 with SMTP id x206mr18316967ywd.7.1442841768122; Mon, 21 Sep 2015 06:22:48 -0700 (PDT) X-Received: by 10.182.98.168 with SMTP id ej8mr78002obb.18.1442841768085; Mon, 21 Sep 2015 06:22:48 -0700 (PDT) Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!mx02.eternal-september.org!feeder.eternal-september.org!news.glorb.com!v79no2650747qge.0!news-out.google.com!f6ni11569igi.0!nntp.google.com!kq10no6081328igb.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail Newsgroups: comp.lang.ada Date: Mon, 21 Sep 2015 06:22:47 -0700 (PDT) In-Reply-To: <871tds56jw.fsf@adaheads.sparre-andersen.dk> Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=194.138.39.55; posting-account=IcHmbgoAAABVfpbjrkJyy4Yb3hmce3tn NNTP-Posting-Host: 194.138.39.55 References: <26b4bb33-0ebc-4181-bea6-07f1e36ca288@googlegroups.com> <871tds56jw.fsf@adaheads.sparre-andersen.dk> User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: <2c064071-2e40-4267-81f6-3196d7ae35ab@googlegroups.com> Subject: Re: Addressing in Object Ada v/s GNAT (2013) showing Vast Differences From: Lucas Redding Injection-Date: Mon, 21 Sep 2015 13:22:48 +0000 Content-Type: text/plain; charset=ISO-8859-1 Xref: news.eternal-september.org comp.lang.ada:27799 Date: 2015-09-21T06:22:47-07:00 List-Id: On Monday, September 21, 2015 at 12:57:09 PM UTC+1, Jacob Sparre Andersen wrote: > Lucas Redding wrote: > > Your examples don't compile. Please show us the actual code. > > Greetings, > > Jacob > -- > "Very small. Go to sleep" - monster (not drooling) Hi Jacob thanks for that. I am avoiding having to flood this with tons of code. So here is a compiled example. package interface_p is type sixteen_bits is range 0..(2**16)-1 ; type fourteen_bits is range 0..(2**14)-1; type ten_bits is range 0..(2**10)-1; type padding_bits is range 0..(2**8)-1 ; type rec is record a: fourteen_bits ; b: ten_bits ; padding : padding_bits ; end record ; for rec use record a at 0 range 0..13 ; b at 0 range 14..23 ; padding at 0 range 24..31; end record ; for rec'size use 32; for rec'alignment use 1; subtype local_fourteen_bits is sixteen_bits range 0 .. (2 ** 14)-1; subtype local_ten_bits is sixteen_bits range 0 .. (2 ** 10)-1; type local_rec is record a : local_fourteen_bits ; b : local_ten_bits ; end record; for local_rec use record a at 0 range 0 .. 13 ; b at 2 range 0 .. 9 ; end record; for local_rec'size use 32 ; for local_rec'Alignment use 1 ; VAR_REC : rec := (a => 1, b => 2, padding => 0 ) ; -- I explicitly assign here but in actual application it maps onto a 32 bit -- record in memory. I have deliberately changed in order to avoid adding -- tons of irrelevant code. function READ_RECORD return local_rec ; end interface_p ; package body INTERFACE_P is function READ_RECORD return local_rec is VAR_LOCAL_REC : local_rec ; begin -- We would like to copy the information once to a byte aligned -- record to hopefully speed up -- access to this item because it is accessed internally a large -- number of times. VAR_LOCAL_REC.a := local_fourteen_bits(VAR_REC.a) ; VAR_LOCAL_REC.b := local_ten_bits(VAR_REC.b) ; -- The problem is when I copy each record component to the local copies -- (including the typecast) -- my var_local_rec.a takes on a 16 bit value and thus includes the bit values -- from var_rec.b ; -- So if var_rec.a is 1 and var_rec.b is 2 I end up with the following in -- var_local_rec in GNAT Ada : -- var_local_rec.a = 32769 ; -- var_local_rec.b = 2 ; -- Clearly this is wrong. And although I have set all checks in the compiler I -- don't get an overflow error which is what I would expect. -- In Object Ada I get : -- var_local_rec.a = 1 ; -- var_local_rec.b = 2; return VAR_LOCAl_REC ; end READ_RECORD ; end INTERFACE_P ;