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From: Dan.Pop@cern.ch (Dan Pop)
Subject: Re: How big is an int? (was: Yet another stupid language war (was:
 ... the only languages you need!!))
Date: 1997/11/10
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Date: 1997-11-10T00:00:00+00:00
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In <873814384snz@genesis.demon.co.uk> fred@genesis.demon.co.uk (Lawrence Kirby) writes:

>In article <danpop.878913108@news.cern.ch> Dan.Pop@cern.ch "Dan Pop" writes:
>
>>Can a strictly conforming program perform *any* kind of I/O?
>
>Yes.

Please provide an example.

>> Part
>>of the definition of "strictly conforming program" says:
>>
>>    It shall not produce output dependent on any unspecified, undefined, or
>>    implementation-defined behavior...
>
>However that doesn't mean that a strictly conforming program has to produce
>the same output every time you run it. If that were true a program which
>wrote output derived from rand() could not be strictly conforming (and it
>can).

Nope, it cannot.  The behaviour of rand() is unspecified.  Also code using
floating point arithmetic or most of the functions from <math.h> cannot
be strictly conforming.

>>It is unspecified (or maybe implementation-defined) when an I/O operation
>>fails and if that failure affects the behaviour of your program...
>
>No, it isn't. The standard states explicitly all cases of unspecified and
>implementation-defined behaviour, these terms are very specific.
>Only undefined behaviour can result from a lack of definition, and even
>then only from a *total* lack of definition (or there is a defect in the
>standard). getc() (for example) has no unspecified and no
>implementation-defined behaviour (*).

You missed the point.  It is undefined when the well defined conditions
that lead to the failure of a stdio function occur.  But the behaviour of
the program depends on the occurence of these conditions.

Dan
--
Dan Pop
CERN, IT Division
Email: Dan.Pop@cern.ch 
Mail:  CERN - PPE, Bat. 31 1-014, CH-1211 Geneve 23, Switzerland