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Date: Sat, 18 Jun 2005 00:59:00 -0000
Subject: Re: basic VRP min/max range overflow question
From: Paul Schlie <schlie@comcast.net>
To: Andrew Pinski <pinskia@physics.uc.edu>
CC: Paolo Bonzini <paolo.bonzini@lu.unisi.ch>,
	GCC Development <gcc@gcc.gnu.org>,
	Diego Novillo <dnovillo@redhat.com>
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> From: Andrew Pinski <pinskia@physics.uc.edu>
> On Jun 17, 2005, at 8:20 PM, Paul Schlie wrote:
> 
>>   ["undefined" only provides liberties within the constrains of what
>>   is specifically specified as being undefined, but none beyond that.]
> 
> That is not true.  Undefined means it can run "rm /" if you ever invoke
> the undefined code.

- If the semantics of an operation are "undefined", I'd agree; but if
  control is returned to the program, the program's remaining specified
  semantics must be correspondingly obeyed, including the those which
  may utilize the resulting value of the "undefined" operation.

- If the result value is "undefined", just the value is undefined.

(Unless one advocates that any undefined result implies undefined semantics,
which enables anything to occur, including the arbitrary corruption of
the remaining program's otherwise well defined semantics; in which case any
invocation of implementation specific behavior may then validly result in
arbitrary remaining program behavior.)

Which I'd hope isn't advocated.