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0 pointsIzkata9mo ago0 comments

Isn't i going to be one past end on the last iteration?

I think you want either "++i <= end" or "i++ < end", and that's assuming "end" is inclusive. If it's exclusive then "++i < end", right?

(Using "<=" in a termination condition has become a code smell for me, it's been wrong more often than not, so it sticks out as "pay close attention here")

0 comments

chowells9mo ago

Actually, I think what you really need is "i++ != end". The whole point was inequalities don't work how you want when end is INT_MAX. You want to just terminate after the loop body where i was equal to end. Except now I'm not sure if that evades the UB of a signed int exceeding INT_MAX. I don't know C well enough to know if the UB is in performing the increment or reading the value afterwards.

Edit: Just checked in with a C expert. The UB is in the increment operation, so that's not correct after all. You really do just need to separate out the update from the test entirely.

trealira9mo ago

Yeah, it would have to be something like this if you wanted to avoid the signed integer overflow at the end of the loop:

  assert(i <= j);
  for (;;) {
      do_something_with(i);
      if (i == j)
          break;
      i++;
  }

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