Re: Git Test Coverage Report (Mon. Dec 9)

[Derrick Stolee <stolee@gmail.com>]

On 12/9/2019 12:19 PM, Eric Sunshine wrote:
> On Mon, Dec 9, 2019 at 12:11 PM René Scharfe <l.s.r@web.de> wrote:
>> Am 09.12.19 um 16:36 schrieb Derrick Stolee:
>>> René Scharfe  0bb313a5 xdiff: unignore changes in function context
>>> xdiff/xemit.c
>>> 0bb313a5 223)        xchp->i1 + xchp->chg1 <= s1 &&
>>> 0bb313a5 224)        xchp->i2 + xchp->chg2 <= s2)
>>> 0bb313a5 225) xchp = xchp->next;
>>
>> Hmm, line 223 *is* exercised by t4015.85.
> 
> This, along with Dscho's[1] review of an earlier coverage report,
> makes one wonder if there is some off-by-one error in the reporting
> logic, such that it is reporting the wrong lines as not covered.

This is definitely possible. I'll see if I can locate the bug in
my report-generation code.

However, line 222 is here [1]

	while (xchp != xch &&

So if this is always false, then the rest of the while condition
will not be tested, nor will the body (line 225: xchp = xchp->next;).

If it's just an off-by-one error in either direction, then line 224
still is definitely not covered (which would imply that 225 is not
covered, either).
 
> Footnotes:
> 
> [1]: https://lore.kernel.org/git/nycvar.QRO.7.76.6.1911262116100.31080@tvgsbejvaqbjf.bet/
> which, among other seeming anomalies pointed out by Dscho, showed a
> closing brace '}' not covered by a test:
> 
>     > Johannes Schindelin 867bc1d2 rebase-merges: ...
>     > sequencer.c
>     > 867bc1d2 4539) }
> 
>     Not sure why this closing parenthesis isn't covered :-D

That closing paren is the end of a for loop [2] that has an if (*) break; inside.
The closing paren _could_ be uncovered if the "break;" is hit every time.

So, these seem like reasonable lines to report as uncovered. However, I'll
continue to look for a problem in my code as I would hate to cause readers
to stress over an actually-covered line.

Thanks,
-Stolee

[1] https://github.com/git/git/blob/e0522318ac56aeb88f14e72ba2db25912e9972de/xdiff/xemit.c#L223
[2] https://github.com/git/git/blob/083378cc35c4dbcc607e4cdd24a5fca440163d17/sequencer.c#L4539