boost::counting_iterator

[nobody]

The following example code

boost::counting_iterator<int> pi1(3);
boost::counting_iterator<int> pi2(7);
printf("diff %d, %d\n", pi2 - pi1, 5);

should print
  diff 4, 5
but instead wrongly prints
  diff 4, 0

Tested with gcc.

[ljj116]

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It's because the subtraction results in a 64-bit number.  %d is only expecting 32 bits, so the first 32 bits from the stack goes to the first %d and the second 32 bits goes to the second %d.  The third 32-bits (5) is never accessed by the printf function.

If you really want to do that, use:
printf("diff %d, %d\n", (int)(pi2 - pi1), 5);

The same thing happens if you use this code on a machine where long long is 64 bits:
long long my64bitnum = 4;
printf("diff %d, %d\n", my64bitnum, 5);

[ljj116]

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or 
printf("diff %lld, %d\n", pi2 - pi1, 5); 

if you want all 64 bits.

[david_abrahams]

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Closing since this is clearly not a bug in counting_iterator.  Use C++ iostreams or Boost.Format if you want typesafe I/O.