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Re: warning: dereferencing type-punned pointer will break strict-aliasing rules

From: Nathan Sidwell <nathan at codesourcery dot com>
To: gcc-help at gcc dot gnu dot org
Cc: jeffreyholle at bellsouth dot net
Date: Thu, 26 Jul 2007 19:12:07 +0100
Subject: Re: warning: dereferencing type-punned pointer will break strict-aliasing rules
References: <f8600s$ad$1@sea.gmane.org> <46A687E1.76D5243B@dessent.net>

Brian Dessent wrote:

Jeffrey Holle wrote:

On release builds, wxWidgets code emits a lot of these warnings:
   warning: dereferencing type-punned pointer will break strict-aliasing
rules

Questions:

   1.  Are these warnings benign?  If so can they be suppressed?
   2.  If not, what level of optimization should I regress to avoid these
warnings?


I would certainly not ignore them.  They indicate that the code being
compiled probably violates the ISO C standard rules for type aliasing,

which _may_ break the aliasing rules.

If you examine the code being warned about, and find it benign, you may insert an intermediate void * cast to silence the warning.

nathan

--
Nathan Sidwell    ::   http://www.codesourcery.com   ::         CodeSourcery
nathan@codesourcery.com    ::     http://www.planetfall.pwp.blueyonder.co.uk

References:
- warning: dereferencing type-punned pointer will break strict-aliasing rules
  - From: Jeffrey Holle
- Re: warning: dereferencing type-punned pointer will break strict-aliasing rules
  - From: Brian Dessent

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