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Date: Sun, 15 May 2011 20:15:07 -0400
From: pete <pfiland@mindspring.com>
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Subject: Re: I need help
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.c:4040

pete wrote:
> 
> Eric Sosman wrote:
> >
> > On 5/15/2011 5:37 PM, sandeep wrote:
> > > Eric Sosman writes:
> > >>      char *space = strchr(karmarkar, ' '); if (space == NULL)
> > >>          printf ("No spaces\n");
> > >>      else
> > >>          printf ("First space is at position %u\n",
> > >>              (unsigned)(space - karmarkar));
> > >
> > > This could give the wrong answer on implementations
> > > where PTRDIFF_MAX > UINT_MAX.
> >
> >      Thank you so very, very much for this helpful observation,
> > guaranteed to clarify matters for the O.P.
> 
> sandeep is wrong.
> The context (snipped by sandeep)
> for which your code was written, is this:
>     char* karmarkar = "Karmarkar   958572";
> 
> And in that context, there is no way that the difference
> between (space) and (karmarkar) can excede either UINT_MAX
> or PTRDIFF_MAX (which would be a different C trivia point).

I should have been more clear.
Whether or not (PTRDIFF_MAX > UINT_MAX) is true, is irrelevant.
This code cannot give the wrong answer.

What matters, 
in terms of whether or not the code is undefined, 
is whether or not (space - karmarkar)
is representable as a ptrdiff_t value.

Since (space - karmarkar)
is representable as a ptrdiff_t value,
then what matters, 
in terms of whether or not the code outputs the correct answer,
is whether or not (space - karmarkar) 
is less than or equal to UINT_MAX.

-- 
pete