From: Junio C Hamano <gitster@pobox.com>
To: Kevin Willford <kcwillford@gmail.com>
Cc: 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: Fri, 29 Jul 2016 13:47:37 -0700 [thread overview]
Message-ID: <xmqqoa5gmas6.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <20160729161920.3792-2-kcwillford@gmail.com> (Kevin Willford's message of "Fri, 29 Jul 2016 12:19:17 -0400")
Kevin Willford <kcwillford@gmail.com> writes:
> From: Kevin Willford <kewillf@microsoft.com>
>
> This change will use the hashmap from the hashmap.h to keep track of the
> patch_ids that have been encountered instead of using an internal
> implementation. This simplifies the implementation of the patch ids.
>
> Signed-off-by: Kevin Willford <kcwillford@gmail.com>
> ---
> patch-ids.c | 86 +++++++++++++++++++++----------------------------------------
> patch-ids.h | 7 +++--
> 2 files changed, 32 insertions(+), 61 deletions(-)
The patch text itself is almost unreadble because of a lot of
verbose code it had to carry before this change, and the removal of
that unreadable code of course is the point of this very welcome
clean-up ;-). The resulting code is very readable.
> struct patch_id *has_commit_patch_id(struct commit *commit,
> struct patch_ids *ids)
> {
> - return add_commit(commit, ids, 1);
> + struct patch_id patch;
> +
> + memset(&patch, 0, sizeof(patch));
> + if (init_patch_id_entry(&patch, commit, ids))
> + return NULL;
> + return hashmap_get(&ids->patches, &patch, NULL);
> }
>
> struct patch_id *add_commit_patch_id(struct commit *commit,
> struct patch_ids *ids)
> {
> - return add_commit(commit, ids, 0);
> + struct patch_id *key = xcalloc(1, sizeof(*key));
> +
> + if (init_patch_id_entry(key, commit, ids)) {
> + free(key);
> + return NULL;
> + }
This is a tangent, but this made me wonder if it is safe to simply
free(3) the result of calling hashmap_entry_init() which is called
in init_patch_id_entry(). It would obviously become a resource
leak, if a hashmap_entry (which the api documentation says is "an
opaque structure") holds any allocated resource.
The fact that hashmap_entry_init() is there but there is no
corresponding hashmap_entry_clear() hints that there is nothing to
be worried about and I can see from the implementation of
hashmap_entry_init() that no extra resource is held inside, but an
API user should not have to guess. We may want to do one of the two
things:
* document that an embedded hashmap_entry does not hold any
resource that need to be released and it is safe to free the user
structure that embeds one; or
* implement hashmap_entry_clear() that currently is a no-op.
If we anticipate that the hashmap implementation may gain more
fields in this "opaque" structure, the latter might be a more
future-proof approach, as all the callers of hashmap_entry_init()
would already be calling hashmap_entry_clear() to clean it up when
such a change to the hashmap implementation happens. On the other
hand, a caller that does not call hashmap_entry_clear() would not be
noticed by anybody as leaking resources until such a change happens,
so the future-proofing may not have much practical value (iow, the
existing callers of _init() would need to be audited anyway to make
sure they also call _clear()).
next prev parent reply other threads:[~2016-07-29 20:47 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 [this message]
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
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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