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 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,703c4f68db81387d X-Google-Thread: 109fba,703c4f68db81387d X-Google-Thread: 115aec,703c4f68db81387d X-Google-Thread: f43e6,703c4f68db81387d X-Google-Attributes: gid103376,gid109fba,gid115aec,gidf43e6,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news4.google.com!newsfeed.stanford.edu!newsmi-us.news.garr.it!newsmi-eu.news.garr.it!NewsITBone-GARR!irazu.switch.ch!switch.ch!news.grnet.gr!newsfd02.forthnet.gr!not-for-mail From: Ioannis Vranos Newsgroups: comp.lang.ada,comp.lang.c++,comp.realtime,comp.software-eng Subject: Re: [OT] Re: Teaching new tricks to an old dog (C++ -->Ada) Date: Tue, 29 Mar 2005 06:10:21 +0300 Organization: FORTHnet S.A., Atthidon 4, GR-17671 Kalithea, Greece, Tel: +30 2109559000, Fax: +30 2109559333, url: http://www.forthnet.gr Message-ID: <1112065820.885929@athnrd02> References: <4229bad9$0$1019$afc38c87@news.optusnet.com.au> <1110032222.447846.167060@g14g2000cwa.googlegroups.com> <871xau9nlh.fsf@insalien.org> <3SjWd.103128$Vf.3969241@news000.worldonline.dk> <87r7iu85lf.fsf@insalien.org> <1110052142.832650@athnrd02> <1lr611thktbau$.1dj95z21h7l5v.dlg@40tude.net> <1112022773.497341@athnrd02> <1112026376.920221@athnrd02> <1112034544.645999@athnrd02> <1112039976.169686@athnrd02> <1112045099.679682@athnrd02> NNTP-Posting-Host: athnrd02.forthnet.gr Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Trace: athprx02.forthnet.gr 1112065820 32598 193.92.150.73 (29 Mar 2005 03:10:20 GMT) X-Complaints-To: abuse@forthnet.gr NNTP-Posting-Date: Tue, 29 Mar 2005 03:10:20 +0000 (UTC) User-Agent: Mozilla Thunderbird 1.0.2 (Windows/20050317) X-Accept-Language: en-us, en In-Reply-To: Cache-Post-Path: newsfd02!unknown@ppp11-adsl-150.ath.forthnet.gr Xref: g2news1.google.com comp.lang.ada:10105 comp.lang.c++:47721 comp.realtime:1803 comp.software-eng:5446 Date: 2005-03-29T06:10:21+03:00 List-Id: REH wrote: >>#include >>#include >> >>class SomeClass >>{ >> public: >> >> double d; >> int i; >> float f; >> long l; >>}; >> >> >>int main() >>{ >> using namespace std; >> >> unsigned char array[sizeof(SomeClass)]; >> >> SomeClass obj= {1, 2, 3, 4}; >> >> memcpy(array, &obj, sizeof(obj)); >> >> SomeClass *p= reinterpret_cast(array); >> >> cout<d<<" "<i<<" "<f<<" "<l<<"\n"; >>} >> >> >>C:\c>temp >>1 2 3 4 >> >>C:\c> >> >> >>So since this is *guaranteed* to be portable, why this isn't? >> >> >>#include >>#include >> >>class SomeClass >>{ >> public: >> >> double d; >> int i; >> float f; >> long l; >>}; >> >> >>int main() >>{ >> using namespace std; >> >> unsigned char array[sizeof(SomeClass)]; >> >> SomeClass obj= {1, 2, 3, 4}; >> >> SomeClass *p= new(array)SomeClass(obj); >> >> cout<d<<" "<i<<" "<f<<" "<l<<"\n"; >>} >> >> >>C:\c>temp >>1 2 3 4 >> >>C:\c> >> >> >>-- >>Ioannis Vranos >> > > No, NEITHER is portable! That both have alignment issues! Both exihibit > undefined behavior. Show me where in the standard is says you may cast a > pointer to a char array to a pointer of any other type (other than another > signed/unsigned char*) and access it. You do this on a system that cannot > handle misaligned accesses, and your program will most likely crash! Perhaps you are right. If you have the standard, have a look at 3.9-2, 3.9-4, and 3.9-5 which I think agrees with you. -- Ioannis Vranos http://www23.brinkster.com/noicys