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


  • Subject: Re: dereferencing type-punned pointer will break strict-aliasing rules
  • From: Devang Patel <email@hidden>
  • Date: Fri, 19 May 2006 09:14:56 -0700


On May 19, 2006, at 12:26 AM, Michael Monscheuer wrote:

Hi!

Switching ON Auto-vectorization seems to switch on strict aliasing implicitly.

Yes.

Documentation of compiler settings and GUI ('Enforce Strict Aliasing' option)
do not reflect this in XCode

It is a summary, not complete documentation. Open 'cc' man page (either in terminal window or Xcode->Help->Open Man Page) and search for vectorization. It mentions that -fstrict-aliasing is enabled by auto-vectorization. 'cc' man page includes lots of info about other compiler settings.


(All tested with -O3 and -Os. With optimization level -O0
Auto-vectorization option is ignored).

You do not have aliasing warnings with development configurations, as Xcode switches off
optimization in that case (-O0) to enable debugging, I think.

True.

-
Devang

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References: 
 >dereferencing type-punned pointer will break strict-aliasing rules (From: Ulf Dunkel <email@hidden>)
 >Re: dereferencing type-punned pointer will break strict-aliasing rules (From: Eric Albert <email@hidden>)
 >Re: dereferencing type-punned pointer will break strict-aliasing rules (From: Michael Monscheuer <email@hidden>)

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