Re: basic VRP min/max range overflow question

["Joseph S. Myers" <joseph at codesourcery dot com>]

On Sat, 18 Jun 2005, Paul Schlie wrote:

> > You appear to have confused unspecified behavior (where the possibilities
> > are bounded) and undefined behavior (where the possibilities are
> > unbounded).  On *undefined* behavior (such as signed integer overflow),
> > *this International Standard imposes no requirements*.  If a program
> > execution involved undefined behavior, *there are no requirements on its
> > execution, even before the undefined behavior occurs in the abstract
> > machine*.
> 
> No, the standard clearly states that it imposes no requirements on the
> behavior which an implementation may choose to implement for (and limited
> to) that specific undefined behavior; as regardless of that behavior, it's
> resulting side effects clearly remains constrained by the rules as specified
> in 5.1.2.3.
> 
>        [#1] Behavior where this International Standard provides two
>        or  more  possibilities and imposes no requirements on which
>        is chosen in any instance.  A program that is correct in all
>        other   aspects,   operating  on  correct  data,  containing
>        unspecified behavior shall be a correct program and  act  in
>        accordance with subclause 5.1.2.3.

1. This section describes unspecified behavior, not undefined behavior.  
This discussion is about undefined behavior, not unspecified behavior.  
You appear to be trying deliberately to confuse the matter by misleading 
quotation of a section about something other than the topic (undefined 
behavior) under discussion.  You also appear to have removed the heading 
"unspecified behavior" of this section which would show that your 
quotation is irrelevant, in order to confuse readers who don't check 
quotations claiming to be from the standard to see whether they are 
genuine and relevant.

2. No section with the wording you quote appears in the standard; you 
appear to be conflating two different sections, 3.4.4#1 and 4#3.

3. 3.4.4#1 had "use of an unspecified value, or other " prepended in TC2, 
so you are *misquoting* an *obsolete* standard version.

"undefined" and "unspecified" have completely different meanings in C 
standard context.  Until you understand this and are willing to refer only 
to relevant parts of the correct standard version without silently 
concatenating different sections and removing the section headings where 
they would contradict your claims, there is no point in your posting to 
this list or anywhere else C standards are discussed, and readers must 
presume that what you post claiming to be a quotation from the standard is 
not such a quotation or is placed in misleading context until they check 
the standard themselves.

-- 
Joseph S. Myers               http://www.srcf.ucam.org/~jsm28/gcc/
    jsm@polyomino.org.uk (personal mail)
    joseph@codesourcery.com (CodeSourcery mail)
    jsm28@gcc.gnu.org (Bugzilla assignments and CCs)