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
