Re: [PATCH 2/3] approxidate: handle pending number for "specials"

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> On Tue, Nov 06, 2018 at 04:48:28PM -0800, Carlo Arenas wrote:
>
> I think date_yesterday() is the only one of those special functions that
> gets called like this. Here's what I think we should do to fix it (this
> can go right on top of jk/misc-unused-fixes, which is already in next).

Thanks, both.  I think the patch makes sense.

> -- >8 --
> Subject: [PATCH] approxidate: fix NULL dereference in date_time()
>
> When we see a time like "noon", we pass "12" to our date_time() helper,
> which sets the hour to 12pm. If the current time is before noon, then we
> wrap around to yesterday using date_yesterday(). But unlike the normal
> calls to date_yesterday() from approxidate_alpha(), we pass a NULL "num"
> parameter. Since c27cc94fad (approxidate: handle pending number for
> "specials", 2018-11-02), that causes a segfault.
>
> One way to fix this is by checking for NULL. But arguably date_time() is
> abusing our helper by passing NULL in the first place (and this is the
> only case where one of these "special" parsers is used this way). So
> instead, let's have it just do the 1-day subtraction itself. It's still
> just a one-liner due to our update_tm() helper.
>
> Note that the test added here is a little funny, as we say "10am noon",
> which makes the "10am" seem pointless.  But this bug can only be
> triggered when it the currently-parsed hour is before the special time.
> The latest special time is "tea" at 1700, but t0006 uses a hard-coded
> TEST_DATE_NOW of 1900. We could reset TEST_DATE_NOW, but that may lead
> to confusion in other tests. Just saying "10am noon" makes this test
> self-contained.
>
> Reported-by: Carlo Arenas <carenas@gmail.com>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
>  date.c          | 2 +-
>  t/t0006-date.sh | 1 +
>  2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/date.c b/date.c
> index 7adce327a3..9bc15df6f9 100644
> --- a/date.c
> +++ b/date.c
> @@ -929,7 +929,7 @@ static void date_yesterday(struct tm *tm, struct tm *now, int *num)
>  static void date_time(struct tm *tm, struct tm *now, int hour)
>  {
>  	if (tm->tm_hour < hour)
> -		date_yesterday(tm, now, NULL);
> +		update_tm(tm, now, 24*60*60);
>  	tm->tm_hour = hour;
>  	tm->tm_min = 0;
>  	tm->tm_sec = 0;
> diff --git a/t/t0006-date.sh b/t/t0006-date.sh
> index b7ea5fbc36..ffb2975e48 100755
> --- a/t/t0006-date.sh
> +++ b/t/t0006-date.sh
> @@ -114,6 +114,7 @@ check_approxidate '15:00' '2009-08-30 15:00:00'
>  check_approxidate 'noon today' '2009-08-30 12:00:00'
>  check_approxidate 'noon yesterday' '2009-08-29 12:00:00'
>  check_approxidate 'January 5th noon pm' '2009-01-05 12:00:00'
> +check_approxidate '10am noon' '2009-08-29 12:00:00'
>  
>  check_approxidate 'last tuesday' '2009-08-25 19:20:00'
>  check_approxidate 'July 5th' '2009-07-05 19:20:00'