Re: [PATCH 02/11] t8001/t8002: blame: demonstrate -L bounds checking bug

[Eric Sunshine <sunshine@sunshineco.com>]

On Mon, Aug 5, 2013 at 3:35 PM, Eric Sunshine <sunshine@sunshineco.com> wrote:
> On Mon, Aug 5, 2013 at 3:29 PM, Junio C Hamano <gitster@pobox.com> wrote:
>> Eric Sunshine <sunshine@sunshineco.com> writes:
>>
>>> A bounds checking bug allows the X in -LX to extend one line past the
>>> end of file. For example, given a file with 5 lines, -L6 is accepted as
>>> valid. Demonstrate this problem.
>>>
>>> While here, also add tests to check that the remaining cases of X and Y
>>> in -LX,Y are handled correctly at and in the vicinity of end-of-file.
>>>
>>> Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
>>> ---
>>>  t/annotate-tests.sh | 22 ++++++++++++++++++++++
>>>  1 file changed, 22 insertions(+)
>>>
>>> diff --git a/t/annotate-tests.sh b/t/annotate-tests.sh
>>> index 3524eaf..02fbbf1 100644
>>> --- a/t/annotate-tests.sh
>>> +++ b/t/annotate-tests.sh
>>> @@ -225,10 +225,32 @@ test_expect_success 'blame -L /RE/,-N' '
>>>       check_count -L/99/,-3 B 1 B2 1 D 1
>>>  '
>>>
>>> +# 'file' ends with an incomplete line, so 'wc' reports one fewer lines than
>>> +# git-blame sees, hence the last line is actually $(wc...)+1.
>>> +test_expect_success 'blame -L X (X == nlines)' '
>>> +     n=$(expr $(wc -l <file) + 1) &&
>>> +     check_count -L$n C 1
>>
>> This is somewhat curious.
>>
>> Does the problem triggers only on a file that ends with an
>> incomplete line, or the test was inserted at this location only
>> because it was convenient and the problem exists with or without the
>> incomplete final line?
>>
>> I am guessing that it is the latter.
>
> The problem exists with and without the incomplete line. The comment
> mentioning "incomplete line" and "wc" was inserted to explain why it
> was necessary to add one to the result of wc, which might not
> otherwise be obvious.

Would the comment be clearer if phrased like this?

  # We want to test -LX where X is the last line of the file, so we need
  # to compute the number of lines in the file, which normally would be
  # done via 'wc -l'.  In this case, however, the last line of 'file' is
  # incomplete, so 'wc' reports one fewer than the actual line count. To
  # adjust for this anomaly, we must add one to the result of 'wc'.