From: Derrick Stolee <stolee@gmail.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH 7/9] commit-graph: drop count_distinct_commits() function
Date: Fri, 4 Dec 2020 15:47:43 -0500 [thread overview]
Message-ID: <05c616b0-138a-3e30-5a71-4ba9fb26e6ef@gmail.com> (raw)
In-Reply-To: <X8qfRDsfLYTDL3HV@coredump.intra.peff.net>
On 12/4/2020 3:42 PM, Jeff King wrote:
> On Fri, Dec 04, 2020 at 03:06:24PM -0500, Derrick Stolee wrote:
>
>> On 12/4/2020 1:56 PM, Jeff King wrote:
>>> That turns out not to be a problem, though. The only things we do with
>>> the count are:
>>>
>>> - check if our count will overflow our data structures. But the limit
>>> there is 2^31 commits, so it's not likely to happen in practice.
>>
>> You do point out that you are removing this logic, done in this
>> if statement:
>>
>>> - if (count_distinct >= GRAPH_EDGE_LAST_MASK) {
>>> - error(_("the commit graph format cannot write %d commits"), count_distinct);
>>> - res = -1;
>>> - goto cleanup;
>>> - }
>>
>> What is the harm of keeping this? I know it is very unlikely, but
>> I'd rather fail here than write a commit-graph that gets parsed as
>> garbage.
>
> I agree it's important to have. But this one is redundant. Look a few
> lines below this hunk, and we have:
>
> copy_oids_to_commits(ctx);
>
> if (ctx->commits.nr >= GRAPH_EDGE_LAST_MASK) {
> error(_("too many commits to write graph"));
> res = -1;
> goto cleanup;
> }
Yep, my fault for not looking further in the context of your patch.
> So before we were counting distinct commits, checking that our count
> fits, and then _ignoring_ that count in order to create the actual list
> of commits, and then checking that the actual list's count fits. We only
> need one of those checks, and the important one is the one from the
> actual list (they _should_ match, but due to the bug, they sometimes
> didn't).
>
> My "not likely to happen in practice" is not about the quality of the
> check, but rather that being off by one would never matter in practice.
>
> Does that make more sense?
Makes sense to me. No need to change this patch at all.
Thanks,
-Stolee
next prev parent reply other threads:[~2020-12-04 20:48 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-04 18:48 [PATCH 0/9] misc commit-graph and oid-array cleanups Jeff King
2020-12-04 18:48 ` [PATCH 1/9] oid-array.h: drop sha1 mention from header guard Jeff King
2020-12-04 18:49 ` [PATCH 2/9] t0064: drop sha1 mention from filename Jeff King
2020-12-04 18:50 ` [PATCH 3/9] t0064: make duplicate tests more robust Jeff King
2020-12-04 18:51 ` [PATCH 4/9] cache.h: move hash/oid functions to hash.h Jeff King
2020-12-04 18:52 ` [PATCH 5/9] oid-array: make sort function public Jeff King
2020-12-04 18:53 ` [PATCH 6/9] oid-array: provide a for-loop iterator Jeff King
2020-12-04 19:05 ` Taylor Blau
2020-12-04 19:11 ` Taylor Blau
2020-12-04 19:52 ` Jeff King
2020-12-04 19:51 ` Jeff King
2020-12-04 19:18 ` Eric Sunshine
2020-12-04 20:44 ` Jeff King
2020-12-04 20:57 ` Eric Sunshine
2020-12-04 21:54 ` Junio C Hamano
2020-12-07 19:05 ` Jeff King
2020-12-04 18:56 ` [PATCH 7/9] commit-graph: drop count_distinct_commits() function Jeff King
2020-12-04 20:06 ` Derrick Stolee
2020-12-04 20:42 ` Jeff King
2020-12-04 20:47 ` Derrick Stolee [this message]
2020-12-04 20:50 ` Jeff King
2020-12-04 21:01 ` Derrick Stolee
2020-12-05 2:26 ` Ævar Arnfjörð Bjarmason
2020-12-07 19:01 ` Jeff King
2020-12-04 18:57 ` [PATCH 8/9] commit-graph: replace packed_oid_list with oid_array Jeff King
2020-12-04 19:14 ` Taylor Blau
2020-12-04 18:58 ` [PATCH 9/9] commit-graph: use size_t for array allocation and indexing Jeff King
2020-12-04 19:15 ` [PATCH 0/9] misc commit-graph and oid-array cleanups Taylor Blau
2020-12-04 20:08 ` Derrick Stolee
2020-12-07 19:10 ` [PATCH v2 " Jeff King
2020-12-07 19:10 ` [PATCH v2 1/9] oid-array.h: drop sha1 mention from header guard Jeff King
2020-12-07 19:10 ` [PATCH v2 2/9] t0064: drop sha1 mention from filename Jeff King
2020-12-07 19:10 ` [PATCH v2 3/9] t0064: make duplicate tests more robust Jeff King
2020-12-07 19:10 ` [PATCH v2 4/9] cache.h: move hash/oid functions to hash.h Jeff King
2020-12-07 19:10 ` [PATCH v2 5/9] oid-array: make sort function public Jeff King
2020-12-07 19:11 ` [PATCH v2 6/9] oid-array: provide a for-loop iterator Jeff King
2020-12-07 19:11 ` [PATCH v2 7/9] commit-graph: drop count_distinct_commits() function Jeff King
2020-12-07 19:11 ` [PATCH v2 8/9] commit-graph: replace packed_oid_list with oid_array Jeff King
2020-12-07 19:11 ` [PATCH v2 9/9] commit-graph: use size_t for array allocation and indexing Jeff King
2020-12-07 19:26 ` [PATCH v2 0/9] misc commit-graph and oid-array cleanups Derrick Stolee
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