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Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding

From: Paolo Carlini <paolo dot carlini at oracle dot com>
To: Michael Matz <matz at suse dot de>
Cc: Mark Mitchell <mark at codesourcery dot com>, Gabriel Dos Reis <gdr at integrable-solutions dot net>, Richard Guenther <rguenther at suse dot de>, Richard Guenther <richard dot guenther at gmail dot com>, Paolo Bonzini <bonzini at gnu dot org>, gcc-patches at gcc dot gnu dot org, Diego Novillo <dnovillo at google dot com>
Date: Thu, 04 Feb 2010 18:46:50 +0100
Subject: Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
References: <alpine.LNX.2.00.1001221549140.7863@zhemvz.fhfr.qr> <alpine.LNX.2.00.1002021120580.29631@zhemvz.fhfr.qr> <206fcf961002020301h7457f79r73bce737182a7143@mail.gmail.com> <alpine.LNX.2.00.1002021207050.29631@zhemvz.fhfr.qr> <206fcf961002020348n64cc994bte36621f14954a63d@mail.gmail.com> <alpine.LNX.2.00.1002021336180.29631@zhemvz.fhfr.qr> <206fcf961002020638v3f4f62bfja776eee961c3009a@mail.gmail.com> <alpine.LNX.2.00.1002021545490.29631@zhemvz.fhfr.qr> <206fcf961002020711s6efb64fcm14b0de22f75637cc@mail.gmail.com> <Pine.LNX.4.64.1002021759410.18785@wotan.suse.de> <206fcf961002020918m31eade94sf4395f649da25c6@mail.gmail.com> <4B68CF6B.8010608@codesourcery.com> <Pine.LNX.4.64.1002031407130.18785@wotan.suse.de> <4B697B53.6020301@codesourcery.com> <Pine.LNX.4.64.1002031446140.18785@wotan.suse.de>

Hi,

[snip]
> Or wait, would you then also disallow placement new onto individual 
> subobjects of larger objects (be they char[] or not)?
>   
About this, just wanted to point out that in Pittsburgh this paper will
be discussed again

  http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2981.pdf

whereas in Santa Cruz concerns have been raised exactly about those
placement new of subobjects vs aliasing. In my opinion the proposed
solution to the long standing issue with std::pair is otherwise very
nice and I would really encourage you to check it vs aliasing...

Thanks,
Paolo.

Follow-Ups:
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Gabriel Dos Reis

References:
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Richard Guenther
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Gabriel Dos Reis
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Richard Guenther
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Gabriel Dos Reis
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Richard Guenther
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Gabriel Dos Reis
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Richard Guenther
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Gabriel Dos Reis
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Michael Matz
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Gabriel Dos Reis
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Mark Mitchell
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Michael Matz
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Mark Mitchell
- Re: [PATCH] Fix C++ strict-aliasing issues with memcpy folding
  - From: Michael Matz

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