Meaning of implementation def. behaviour (was: Re: C99 IDE for windows)

Richard Heathfield wrote:
santosh said:

<snip>

The definition for implementation defined behaviour in section 3.4 of
n1256, taken in conjunction with the definition for unspecified
behaviour, on which it depends, seems to state pretty strongly that
_all_ the details of an instance of implementation defined behaviour
must be specified.

Fine, but that doesn't mean they can't be rule-based, as long as the
rules are fully specified.

In fact the Standard seems, (at a second glance), to be far more
restrictive that what I said above. I'll take the liberty of including
the relevant citations from n1256.

3.4.4
1 unspecified behavior
use of an unspecified value, or other behavior where this
International Standard provides two or more possibilities and imposes
no further requirements on which is chosen in any instance

3.4.1
1 implementation-defined behavior
unspecified behavior where each implementation documents how the
choice is made

3.4
1 behavior
external appearance or action

Here "unspecified value" is not defined, as far as I can see. However
for each instance of unspecified behaviour it seems that the Standard
provides all possible courses of action and the implementation is
merely required to choose one course from this list, and from this list
only, though the choice needn't be documented. And implementation
defined behaviour is merely a subset of unspecified behaviour where the
implementation's choice needs to be documented.

In light of this interpretation (though I'm sure I've overlooked
something important somewhere), how can the Standard specify the output
of the 'p' conversion specifier as implementation defined if it has not
itself defined the possible forms of that behaviour a conforming
implementation is required to select one from and document it?

<snip>

.

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