Re: [PATCH] diff: remove ternary operator evaluating always to true
- From
Stefan Beller <stefanbeller@googlemail.com>
- Date
- Aug 12, 2013, 08:32 UTC
- Message-ID
- <52089D81.5010506@googlemail.com>
- In-Reply-To
- <7vli471mxy.fsf@alter.siamese.dyndns.org>
On 08/12/2013 07:46 AM, Junio C Hamano wrote:
Show 49 quoted lines
> Jeff King <peff@peff.net> writes:
>
>> On Thu, Aug 08, 2013 at 08:31:44PM +0200, Stefan Beller wrote:
>>
>>> The next occurrences are at:
>>> /* Never use a non-valid filename anywhere if at all possible */
>>> name_a = DIFF_FILE_VALID(one) ? name_a : name_b;
>>> name_b = DIFF_FILE_VALID(two) ? name_b : name_a;
>>>
>>> a_one = quote_two(a_prefix, name_a + (*name_a == '/'));
>>> b_two = quote_two(b_prefix, name_b + (*name_b == '/'));
>>>
>>> In the last line of this block 'name_b' is dereferenced and compared
>>> to '/'. This would crash if name_b was NULL. Hence in the following code
>>> we can assume name_b being non-null.
>>
>> I think your change is correct, but I find the reasoning above a little
>> suspect. It assumes that the second chunk of code (accessing name_a and
>> name_b) is correct, and pins the correctness of the code you are
>> changing to it. If the second chunk is buggy, then you are actually
>> making the code worse.
>
> True. I think the original code structure design is name_a should
> always exist but name_b may not (the caller of run_diff_cmd() that
> eventually calls this call these "name" and "other", and the intent
> is renaming filepair is what needs "other").
>
>> I wonder if the implicit expectation of the function to take at least
>> one non-NULL name would be more obvious if the first few lines were
>> written as:
>>
>> if (DIFF_FILE_VALID(one)) {
>> if (!DIFF_FILE_VALID(two))
>> name_b = name_a;
>> } else if (DIFF_FILE_VALID(two))
>> name_a = name_b;
>> else
>> die("BUG: two invalid files to diff");
>>
>> That covers all of the cases explicitly, though it is IMHO uglier to
>> read (and there is still an implicit assumption that the name is
>> non-NULL if DIFF_FILE_VALID() is true).
>
> I think that is an overall improvement, especially if we also update
> the checks of {one,two}->mode made for the block that deals with
> submodules to use DIFF_FILE_VALID().
>
> Thanks.
> So, do I understand your reasoning, when proposing this patch? (This may break whitespaces as it's copied into my MUA, will resend with git send-mail if you think this is the right thing.)
This patch just covers your discussion and not the previous patches.
Stefan
--8<-- From 701bab4f15598ba230552af7f1d5719187f1b2e8 Mon Sep 17 00:00:00 2001 From: Stefan Beller <stefanbeller@googlemail.com> Date: Mon, 12 Aug 2013 10:29:07 +0200 Subject: [PATCH] diff: Additional error checking for input parameters
This makes the diff function error out instead of segfaulting if the parameters are bad.
Helped-by: Jeff King <peff@peff.net> Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Stefan Beller <stefanbeller@googlemail.com> --- diff.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/diff.c b/diff.c index e53ddad..de21971 100644 --- a/diff.c +++ b/diff.c @@ -2254,8 +2254,11 @@ static void builtin_diff(const char *name_a, (!two->mode || S_ISGITLINK(two->mode))) { const char *del = diff_get_color_opt(o, DIFF_FILE_OLD); const char *add = diff_get_color_opt(o, DIFF_FILE_NEW); - show_submodule_summary(o->file, one ? one->path : two->path, - line_prefix, + struct diff_filespec *spec = one && DIFF_FILE_VALID(one) ? one : two; + if (!spec && !DIFF_FILE_VALID(spec)) + die("BUG: two invalid diff_filespec structs in diff"); + + show_submodule_summary(o->file, spec->path, line_prefix, one->sha1, two->sha1, two->dirty_submodule, meta, del, add, reset); return; @@ -2276,8 +2279,13 @@ static void builtin_diff(const char *name_a, } /* Never use a non-valid filename anywhere if at all possible */ - name_a = DIFF_FILE_VALID(one) ? name_a : name_b; - name_b = DIFF_FILE_VALID(two) ? name_b : name_a; + if (DIFF_FILE_VALID(one)) { + if (!DIFF_FILE_VALID(two)) + name_b = name_a; + } else if (DIFF_FILE_VALID(two)) + name_a = name_b; + else + die("BUG: two invalid files to diff"); a_one = quote_two(a_prefix, name_a + (*name_a == '/')); b_two = quote_two(b_prefix, name_b + (*name_b == '/'));
-- 1.8.4.rc2