From: Junio C Hamano <gitster@pobox.com>
To: Elijah Newren <newren@gmail.com>
Cc: "Andrzej Hunt via GitGitGadget" <gitgitgadget@gmail.com>,
"Git Mailing List" <git@vger.kernel.org>,
"René Scharfe" <l.s.r@web.de>, "Andrzej Hunt" <andrzej@ahunt.org>,
"Andrzej Hunt" <ajrhunt@google.com>
Subject: Re: [PATCH v2] merge-ort: only do pointer arithmetic for non-empty lists
Date: Mon, 12 Apr 2021 10:47:19 -0700 [thread overview]
Message-ID: <xmqqo8eje6oo.fsf@gitster.g> (raw)
In-Reply-To: <CABPp-BE2D933Bc6w-OeaJc1r+1_tvMeK2M-HK4eEKPkQb3BdQQ@mail.gmail.com> (Elijah Newren's message of "Mon, 12 Apr 2021 08:52:14 -0700")
Elijah Newren <newren@gmail.com> writes:
>> /* Pre-allocate some space in buf */
>> extra = hash_size + 8; /* 8: 6 for mode, 1 for space, 1 for NUL char */
>>
>> base-commit: 89b43f80a514aee58b662ad606e6352e03eaeee4
>> --
>> gitgitgadget
>
> Otherwise, this patch looks good to me; thanks!
By the way, I noticed the post-context comment and got curious.
/* Pre-allocate some space in buf */
extra = hash_size + 8; /* 8: 6 for mode, 1 for space, 1 for NUL char */
for (i = 0; i < nr; i++) {
maxlen += strlen(versions->items[offset+i].string) + extra;
}
strbuf_grow(&buf, maxlen);
Because "6 for mode" is wrong if it means "%06o", but the format
used in the code is "%o" so there is no correctness issues in the
code (Phew). This "grow" is to avoid having to repeatedly
reallocate "nr" times in the loop that comes, but
(1) s/6 for mode/up to 6 for mode/ to make it less misleading.
(2) does this preallocation really help performance?
(3) it is really disturbing to find a custom tree-writing code that
is exercised only by ort here. Tree-writing has been one major
source of broken objects in various reimplementation of Git---
all known ones made a mistake sometime in the past---and I'd
strongly prefer to see a single helper that formats a tree
object, given a set of <mode, object name, path> in the longer
code health.
prev parent reply other threads:[~2021-04-12 17:47 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
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 [this message]
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