From: Junio C Hamano <gitster@pobox.com>
To: "René Scharfe" <l.s.r@web.de>
Cc: Andrzej Hunt via GitGitGadget <gitgitgadget@gmail.com>,
git@vger.kernel.org, Elijah Newren <newren@gmail.com>,
Andrzej Hunt <andrzej@ahunt.org>,
Andrzej Hunt <ajrhunt@google.com>
Subject: Re: [PATCH] merge-ort: only do pointer arithmetic for non-empty lists
Date: Sat, 10 Apr 2021 15:56:01 -0700 [thread overview]
Message-ID: <xmqq8s5pkav2.fsf@gitster.g> (raw)
In-Reply-To: <1866b90b-fe07-18df-0d60-e2350d935375@web.de> (=?utf-8?Q?=22R?= =?utf-8?Q?en=C3=A9?= Scharfe"'s message of "Sat, 10 Apr 2021 13:48:18 +0200")
René Scharfe <l.s.r@web.de> writes:
>> diff --git a/merge-ort.c b/merge-ort.c
>> index 5e118a85ee04..4da4b4688336 100644
>> --- a/merge-ort.c
>> +++ b/merge-ort.c
>> @@ -2504,8 +2504,10 @@ static void write_tree(struct object_id *result_oid,
>> * We won't use relevant_entries again and will let it just pop off the
>> * stack, so there won't be allocation worries or anything.
>> */
>> - relevant_entries.items = versions->items + offset;
>> - relevant_entries.nr = versions->nr - offset;
>> + if (versions->nr) {
>> + relevant_entries.items = versions->items + offset;
>> + relevant_entries.nr = versions->nr - offset;
>> + }
>> QSORT(relevant_entries.items, relevant_entries.nr, tree_entry_order);
>
> Reading the diff I was wondering if QSORT now gets handed uninitialized
> values if version-nr is 0. The answer is no -- relevant_entries is
> initialized at declaration. Otherwise the compiler would have probably
> warned, but sometimes it gets confused.
>
> I wonder why relevant_entries is introduced at all, though. It's not
> referenced later. So how about this instead?
>
> if (versions->nr)
> QSORT(versions->items + offset, nr, tree_entry_order);
>
> The intent to sort the last versions->nr-offset entries of versions,
> but only if it's not empty, is easier to see like this, I think.
That does make sense. I wonder if there needs some assertion to
ensure that "offset" does not exceed "versions.nr", though.
next prev parent reply other threads:[~2021-04-10 22:56 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-10 8:30 [PATCH] merge-ort: only do pointer arithmetic for non-empty lists Andrzej Hunt via GitGitGadget
2021-04-10 11:48 ` René Scharfe
2021-04-10 22:56 ` Junio C Hamano [this message]
2021-04-11 9:14 ` Andrzej Hunt
2021-04-11 9:12 ` Andrzej Hunt
2021-04-11 11:05 ` [PATCH v2] " Andrzej Hunt via GitGitGadget
2021-04-12 15:52 ` Elijah Newren
2021-04-12 17:39 ` Junio C Hamano
2021-04-12 17:47 ` Junio C Hamano
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