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Re: Unspecified Behaviors in C90 - part 3

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On 14/07/15 17:33, David Kleinecke wrote:

<snip>

> Not quite - but close. The things listed as unspecified are unspecified
> in different ways and I would like those ways separated. For example,
> the behavior if a printable character is written when the active
> position is at the final position of a line is unspecified because the
> standard is declining to specify the display device but could (and
> should) be documented for any real device.

So we have two choices that I can see - document the behaviour of the 
display device in the display device documentation, or document the 
behaviour of all existing display devices in the Standard (or in the 
implementation's documentation), and update the Standard (or the 
implementation docs) every time a new display device is brought to 
market. If we take the latter course, the Standard (or *every* 
implementation document) immediately increases in length by a 
significant amount, and is almost always out of date. If we adopt the 
former course, people who actually need to know about the 
characteristics of a specific display device can look up those 
characteristics easily, without burdening the rest of the world with 
redundant data. So you are making a good argument for leaving some 
things unspecified. What advantage do you see in forcing implementers to 
document the behaviour of display devices?

> On the other hand the order of evaluation of arguments needs to be
> documented because perhaps the order is predictable.

If the order is predictable, you don't need to document it because you 
can just predict it instead. In fact, the order is not predictable (in 
the sense that more than one reasonable choice can be made and 
implementers do in fact make different choices on occasion), but it 
turns out not to matter because well-written C code doesn't depend on 
order of evaluation (between sequence points).

> A blanket statement is too simple but brief statements will usually
> suffice.

Why is a blanket statement too simple? It seems to me to be perfectly 
reasonable for the Standard to identify a number of areas in which there 
is no need to specify a precise behaviour (e.g. order of evaluation), 
and simply label these areas "unspecified behaviour". That's what the 
Standard does right now. It works. If you want either ISO or 
implementers to change the way they do things, you will need more 
powerful arguments than you have so far supplied.

-- 
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
Sig line 4 vacant - apply within

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Unspecified Behaviors in C90 - part 3 David Kleinecke <dkleinecke@gmail.com> - 2015-07-09 11:21 -0700
  Re: Unspecified Behaviors in C90 - part 3 James Kuyper <jameskuyper@verizon.net> - 2015-07-09 14:54 -0400
    Re: Unspecified Behaviors in C90 - part 3 Richard Heathfield <rjh@cpax.org.uk> - 2015-07-09 21:38 +0100
  Re: Unspecified Behaviors in C90 - part 3 raltbos@xs4all.nl (Richard Bos) - 2015-07-13 21:22 +0000
    Re: Unspecified Behaviors in C90 - part 3 David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 08:21 -0700
      Re: Unspecified Behaviors in C90 - part 3 Keith Thompson <kst-u@mib.org> - 2015-07-14 08:48 -0700
        Re: Unspecified Behaviors in C90 - part 3 David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 09:33 -0700
          Re: Unspecified Behaviors in C90 - part 3 Richard Heathfield <rjh@cpax.org.uk> - 2015-07-14 18:08 +0100
            Re: Unspecified Behaviors in C90 - part 3 David Kleinecke <dkleinecke@gmail.com> - 2015-07-15 19:38 -0700
              Re: Unspecified Behaviors in C90 - part 3 James Kuyper <jameskuyper@verizon.net> - 2015-07-16 00:47 -0400
                Re: Unspecified Behaviors in C90 - part 3 David Kleinecke <dkleinecke@gmail.com> - 2015-07-16 17:10 -0700
                Re: Unspecified Behaviors in C90 - part 3 James Kuyper <jameskuyper@verizon.net> - 2015-07-16 21:17 -0400
                Re: Unspecified Behaviors in C90 - part 3 maddoxr@acm.org - 2015-07-17 07:43 -0700
              Re: Unspecified Behaviors in C90 - part 3 Richard Heathfield <rjh@cpax.org.uk> - 2015-07-16 09:35 +0100
                Re: Unspecified Behaviors in C90 - part 3 David Kleinecke <dkleinecke@gmail.com> - 2015-07-16 17:18 -0700
                Re: Unspecified Behaviors in C90 - part 3 Richard Heathfield <rjh@cpax.org.uk> - 2015-07-17 01:45 +0100
                Re: Unspecified Behaviors in C90 - part 3 James Kuyper <jameskuyper@verizon.net> - 2015-07-16 21:19 -0400
                Re: Unspecified Behaviors in C90 - part 3 James Kuyper <jameskuyper@verizon.net> - 2015-07-17 12:14 -0400
                Re: Unspecified Behaviors in C90 - part 3 Keith Thompson <kst-u@mib.org> - 2015-07-17 11:00 -0700
                Re: Unspecified Behaviors in C90 - part 3 raltbos@xs4all.nl (Richard Bos) - 2015-07-19 21:24 +0000
              Re: Unspecified Behaviors in C90 - part 3 Keith Thompson <kst-u@mib.org> - 2015-07-16 07:40 -0700
                Re: Unspecified Behaviors in C90 - part 3 David Kleinecke <dkleinecke@gmail.com> - 2015-07-16 17:20 -0700
                Re: Unspecified Behaviors in C90 - part 3 Richard Heathfield <rjh@cpax.org.uk> - 2015-07-17 01:49 +0100
          Re: Unspecified Behaviors in C90 - part 3 Keith Thompson <kst-u@mib.org> - 2015-07-14 11:23 -0700
          Re: Unspecified Behaviors in C90 - part 3 James Kuyper <jameskuyper@verizon.net> - 2015-07-14 15:11 -0400
            Re: Unspecified Behaviors in C90 - part 3 David Kleinecke <dkleinecke@gmail.com> - 2015-07-15 19:46 -0700
              Re: Unspecified Behaviors in C90 - part 3 James Kuyper <jameskuyper@verizon.net> - 2015-07-16 01:50 -0400
                Re: Unspecified Behaviors in C90 - part 3 David Kleinecke <dkleinecke@gmail.com> - 2015-07-16 17:15 -0700
                Re: Unspecified Behaviors in C90 - part 3 Richard Heathfield <rjh@cpax.org.uk> - 2015-07-17 01:39 +0100
                Re: Unspecified Behaviors in C90 - part 3 James Kuyper <jameskuyper@verizon.net> - 2015-07-16 22:26 -0400
      Re: Unspecified Behaviors in C90 - part 3 raltbos@xs4all.nl (Richard Bos) - 2015-07-19 21:22 +0000
      Re: Unspecified Behaviors in C90 - part 3 James Kuyper <jameskuyper@verizon.net> - 2015-07-19 17:57 -0400

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