Re: moot and unposixy error message

2008-08-19 Thread Benno Schulenberg 
Andreas Schwab wrote:
 But the sum can overflow, and since the involved types are
 unsigned this has defined (wrap-around) behaviour.

Thanks.  I felt I must be overlooking something, but couldn't figure 
out what.

  Further, the Open Group says that 'od' should not produce an
  error when '-j' plus '-N' is longer than the file, so the above
  section can be removed.

 This is a good point, however.  But end_offset should then be set
 to (uintmax_t)-1 on overflow.

Setting end_offset to the largest possible integer upon overflow 
will probably do the right thing in all practical cases; but if the 
file is really longer than an integer can represent, it would then 
output the wrong number of bytes.  Better print an error message 
instead then.

$ od -j1 -N18446744073709551615 testfile
od: skip-bytes + read-bytes is too large

$ od -j1 -N18446744073709551616 testfile
od: -N argument `18446744073709551616' too large

$ od -j18446744073709551616 -N1 testfile
od: -j argument `18446744073709551616' too large

$ od -j18446744073709551615 -N1 testmail.k
od: skip-bytes + read-bytes is too large

Benno


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moot and unposixy error message

2008-08-18 Thread Benno Schulenberg 

Hi,

In src/od.c around line 1820 it says this:

  if (limit_bytes_to_format)
{
  end_offset = n_bytes_to_skip + max_bytes_to_format;
  if (end_offset  n_bytes_to_skip)
error (EXIT_FAILURE, 0, _(skip-bytes + read-bytes is too large));
}

Since max_bytes_to_format cannot be negative, the second 'if' will 
never trigger, so the whole six lines are moot.

Further, the Open Group says that 'od' should not produce an error 
when '-j' plus '-N' is longer than the file, so the above section 
can be removed.

  http://www.opengroup.org/onlinepubs/7990989775/xcu/od.html --
  If count bytes of input (after successfully skipping, if -j skip 
  is specified) are not available, it will not be considered an error; 
  the od utility will format the input that is available.

Benno


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Re: moot and unposixy error message

2008-08-18 Thread Andreas Schwab 
Benno Schulenberg [EMAIL PROTECTED] writes:

 Hi,

 In src/od.c around line 1820 it says this:

   if (limit_bytes_to_format)
 {
   end_offset = n_bytes_to_skip + max_bytes_to_format;
   if (end_offset  n_bytes_to_skip)
 error (EXIT_FAILURE, 0, _(skip-bytes + read-bytes is too large));
 }

 Since max_bytes_to_format cannot be negative, the second 'if' will 
 never trigger, so the whole six lines are moot.

But the sum can overflow, and since the involved types are unsigned this
has defined (wrap-around) behaviour.

 Further, the Open Group says that 'od' should not produce an error 
 when '-j' plus '-N' is longer than the file, so the above section 
 can be removed.

This is a good point, however.  But end_offset should then be set to
(uintmax_t)-1 on overflow.

Andreas.

-- 
Andreas Schwab, SuSE Labs, [EMAIL PROTECTED]
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
And now for something completely different.


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