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Re: Loop unrolling




On Wed, 3 Jun 1998, Martin von Loewis wrote:

> > i has automatic storage, and its address is never taken, so the compiler
> > might decide to allocate this object to some 'write-only-memory'.
> 
> No, it may not. Modification of i is 'observable behaviour' as per
> [intro.execution]/6. So I want to observe this on the machine in front
> of me. If the compiler optimizes the loop away, I cannot observe it.
> If it would leave the loop, I could observe it, eg. by means of a
> debugger.

What document is this from? I don't recognize it as being part of the
current C standard. Clause 6 of ISO C describes the elements of
the language.

Is that from the C++ DWP? How does it define observable behavior?
Who is the observer?



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