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Re: [PATCH]: Fix PR tree-optimization/21407

Joseph S. Myers wrote:
On Tue, 10 May 2005, Dale Johannesen wrote:

There was quite a bit of discussion of this internal to Apple, and no
agreement was reached.  Geoff strongly takes the position you say;
Mike and I disagree.  The standard seems unclear.

Nick Maclaren's discussion of "What is an object?" deals more with arrays than with structures, but the basic question of what can be done with a given pointer remains the same.

Indeed. Geoff would perhaps seem to be recommending approaching 3, at the bottom of Nick's message, whereas Nick recommends spproach 1.

I don't think that the situation is anywhere as clear as the type-based aliasing rules, which were themselves sufficiently annoying to people that we turned them off by default for a while. And, even those rules have some areas that are still being resolved by the C committee.

It would seem rather dangerous to me to implement this optimization.

Mark Mitchell
CodeSourcery, LLC
(916) 791-8304

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