[TUHS] Unix stories

Steffen Nurpmeso steffen at sdaoden.eu
Thu Jan 5 02:30:17 AEST 2017


Random832 <random832 at fastmail.com> wrote:
 |On Wed, Jan 4, 2017, at 09:54, Ron Natalie wrote:
 |>> I assume you're imagining it as being equivalent to i = j + i + \
 |>> 1, with a redundant store operation.
 |> 
 |> It's what the language standard specifies, not imagination.  C and C++
 |> state that modifying twice between sequence points or using the value
 |> other than to compute the value for a store is undefined behavior.
 |> The languages put no constraint on what may happen when you do this.
 |
 |But I'm talking about the alternate universe in which the person I was
 |replying to is justified in thinking that it's clear what he means, vs a
 |'plausible' implementation that could arise from methods of translating
 |expressions into machine operations (since people don't tend to respond
 |to "it's undefined because it is, and the compiler can arbitrarily mess
 |things up because it's allowed to by the fact that it's undefined"
 |without a plausible theory of why something might ever behave in a way
 |other than the obvious way)

It is clear in assembler, and C was ment, as i understand it, as
a higher-level portable abstraction of assembler.  Which alternate
universe do you refer to?

--steffen


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