From: Junio C Hamano <gitster@pobox.com>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: Kevin Willford <kcwillford@gmail.com>,
git@vger.kernel.org, Kevin Willford <kewillf@microsoft.com>
Subject: Re: [[PATCH v2] 1/4] patch-ids: stop using a hand-rolled hashmap implementation
Date: Tue, 02 Aug 2016 11:04:05 -0700 [thread overview]
Message-ID: <xmqqtwf3dp4a.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <xmqqshunf6lm.fsf@gitster.mtv.corp.google.com> (Junio C. Hamano's message of "Tue, 02 Aug 2016 10:01:09 -0700")
Junio C Hamano <gitster@pobox.com> writes:
> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
>
>> Oh, we are already safely in Unrelated Tangent Land for a while, I would
>> think. Nothing of what we are discussing in this thread has anything to do
>> with Kevin's patch series,...
>
> Oh, no question about that. Go back to my review, to which your
> message I am responding to is a reply to. What you wrote are all
> about things after "This is a tangent, but this made me wonder if it
> is safe to simply free(3) the result...", which pointed out rough
> points in the hashmap API from the API user's point of view and
> suggested a few possible improvement opportunities.
In other words, I'd be happy with a patch like this, outside the
scope of and independent from this series.
When the hashmap_entry structure does acquire references to external
resources (which I wouldn't judge the likelihood of), this paragraph
will become stale, but that is exactly the point at which _clear()
function needs to be added to the API and described here, replacing
this paragraph.
I do not mind having an empty _clear() before that happens, but I do
not think it adds much safety. A disciplined user of the API may
call that empty _clear() to make her code future-proof, but we know
there are undisciplined developers and reviewers and there will be
codepaths that call _init() without calling the empty _clear(), and
we won't notice it. Whoever is adding the real need for _clear()
must audit the codebase at that point _anyway_, and that is why I
think having an empty _clear() before would not buy us much.
Documentation/technical/api-hashmap.txt | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/Documentation/technical/api-hashmap.txt b/Documentation/technical/api-hashmap.txt
index ad7a5bd..1dcec3d 100644
--- a/Documentation/technical/api-hashmap.txt
+++ b/Documentation/technical/api-hashmap.txt
@@ -104,6 +104,11 @@ If `free_entries` is true, each hashmap_entry in the map is freed as well
`entry` points to the entry to initialize.
+
`hash` is the hash code of the entry.
++
+The hashmap_entry structure does not hold references to external resources,
+and it is safe to just discard it once you are done with it (i.e. if
+your structure was allocated with xmalloc(), you can just free(3) it,
+and if it is on stack, you can just let it go out of scope).
`void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata)`::
next prev parent reply other threads:[~2016-08-02 18:10 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-29 16:19 [[PATCH v2] 0/4] Use header data patch ids for rebase to avoid loading file content Kevin Willford
2016-07-29 16:19 ` [[PATCH v2] 1/4] patch-ids: stop using a hand-rolled hashmap implementation Kevin Willford
2016-07-29 20:47 ` Junio C Hamano
2016-08-01 8:54 ` Johannes Schindelin
2016-08-01 20:04 ` Junio C Hamano
2016-08-01 22:34 ` Eric Wong
2016-08-02 10:30 ` Johannes Schindelin
2016-08-02 17:01 ` Junio C Hamano
2016-08-02 18:04 ` Junio C Hamano [this message]
2016-07-29 21:29 ` Junio C Hamano
2016-07-29 16:19 ` [[PATCH v2] 2/4] patch-ids: replace the seen indicator with a commit pointer Kevin Willford
2016-07-29 21:03 ` Junio C Hamano
2016-07-29 16:19 ` [[PATCH v2] 3/4] patch-ids: add flag to create the diff patch id using header only data Kevin Willford
2016-07-29 16:19 ` [[PATCH v2] 4/4] rebase: avoid computing unnecessary patch IDs Kevin Willford
2016-07-29 21:46 ` Junio C Hamano
2016-08-01 8:58 ` Johannes Schindelin
2016-08-01 20:11 ` Junio C Hamano
2016-08-02 9:50 ` Jakub Narębski
2016-08-02 17:06 ` Junio C Hamano
2016-08-02 10:45 ` Johannes Schindelin
2016-08-02 17:08 ` Junio C Hamano
2016-08-04 3:00 ` Junio C Hamano
2016-08-04 14:21 ` Johannes Schindelin
2016-07-29 20:22 ` [[PATCH v2] 0/4] Use header data patch ids for rebase to avoid loading file content Junio C Hamano
2016-08-01 9:01 ` Johannes Schindelin
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