From: "Ángel González" <keisial@gmail.com>
To: Graziano Servizi <Graziano.Servizi@bo.infn.it>
Cc: gcc-help@gcc.gnu.org
Subject: Re: question
Date: Mon, 03 Feb 2014 17:53:00 -0000 [thread overview]
Message-ID: <52EFD783.3030207@gmail.com> (raw)
In-Reply-To: <52EFD3C2.6030209@bo.infn.it>
On 03/02/14 18:37, Graziano Servizi wrote:
> How could this (included) very short code work?
> It isn't a NOT SAFE conversion that made inside void fun?
>
> How can the A pointer know about the B's member f() ?
>
> I'm using gcc 4.8.2 on a Linux Fedora 19 system.
>
> Thanks for your help.
>
> G. Servizi
The a pointer knows nothing about B's member f().
The compiler sees that you are calling B::f(), and calls it (expecting a
B object) with a A object. As B::f() doesn't use anything of B, you are
“lucky†and it happens to run fine. If you were to call a B variable, it
would be accessing random meemory.
Equally, if it had to access the vtable for accesing f(), it would fail,
too. you can mark f() as “virtual†in order to force that and get at
runtime the Segmentation fault you seem to be expecting.
That this invalid code happens to «work» on this compiler version
doesn't make it more legal nor should it be taken as promoting its
(mis)use, etc. etc.
next prev parent reply other threads:[~2014-02-03 17:53 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-03 17:37 question Graziano Servizi
2014-02-03 17:53 ` Ángel González [this message]
2014-02-04 8:11 ` question Jonathan Wakely
-- strict thread matches above, loose matches on Subject: below --
2022-11-29 9:03 Question Mo Alamili
2022-12-02 9:06 ` Question Mo Alamili
[not found] <20200831201750.74266362@arch.localdomain>
[not found] ` <20200903232726.ba28157e5ee86c0dbd76f723@wp.pl>
2020-09-04 22:49 ` Question, using gcc, forum tele
2020-09-04 23:44 ` Question tele
2014-10-07 13:57 Question Graziano Servizi
2014-10-12 12:54 ` Question David Hagood
2014-10-13 9:55 ` Question Jonathan Wakely
2014-07-21 8:51 question Graziano Servizi
2014-07-21 9:10 ` question Jonathan Wakely
2005-10-29 21:02 Question Matias Trocki
2005-10-30 5:00 ` Question Ian Lance Taylor
2004-12-02 15:11 Question Roberto Ausas
2004-12-02 15:25 ` Question Leopold Palomo-Avellaneda
2004-12-02 15:36 ` Question Eljay Love-Jensen
2004-08-19 16:21 question balan
2004-08-19 16:27 ` question Eljay Love-Jensen
2002-06-13 16:17 question Brett Hunt
2002-06-13 10:54 question Antonio Fontinha
1999-12-15 11:06 question petar
1999-12-31 22:24 ` question petar
1999-10-18 10:03 Question Rui Pedro Fernandes
1999-10-31 13:57 ` Question Rui Pedro Fernandes
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