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From: Phillip Wood <phillip.wood123@gmail.com>
To: Eric Wong <e@80x24.org>,
	Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: Junio C Hamano <gitster@pobox.com>, git@vger.kernel.org
Subject: Re: [PATCH 04/11] hashmap_entry: detect improper initialization
Date: Wed, 28 Aug 2019 10:03:56 +0100	[thread overview]
Message-ID: <8beefab6-b7ef-28d3-41d6-c5a5c042ae9a@gmail.com> (raw)
In-Reply-To: <20190827094923.6qhwqosiucsi43td@whir>

Hi Eric

On 27/08/2019 10:49, Eric Wong wrote:
> Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:
>> Hi Eric,
>>
>> On Mon, 26 Aug 2019, Eric Wong wrote:
>>
>>> By renaming the "hash" field to "_hash", it's easy to spot
>>> improper initialization of hashmap_entry structs which
>>> can leave "hashmap_entry.next" uninitialized.
>>
>> Would you mind elaborating a bit? This explanation does not enlighten
>> me, sadly, all I see is that it makes it (slightly) harder for me to
>> maintain Git for Windows' patches on top of `pu`, as the FSCache patches
>> access that field directly (so even if they rebase cleanly, the build
>> breaks).
> 
> I renamed it to intentionally break my build.
> 
> That way I could easily spot if there were any other improper
> initializations of the .hash field.  It's fine to revert,
> actually, it could be more of a "showing my work" patch.

I'm still a bit confused as the changed initializations already used 
hashmap_entry_init() and so presumably were already initializing 
hashmap_entry.next correctly. Is there a way to get 'make coccicheck' 
detect incorrect initializations, this renaming wont prevent bad code 
being added in the future.

Best Wishes

Phillip

> (AFAIK, it's a pretty common practice, but maybe not here :x)
> 
> I've also pondered adding a
> "hashmap_entry_hash(const struct hashmap_entry *)"
> accessor method for reading the field value (but not setting
> it), but it's a bit verbose...
> 
> I'm also wondering where/if hashmap offers a real benefit over
> khash nowadays; the latter ought to have better locality.
> Would like benchmark at some point in the future;
> but safety fixes first :)
> 

  parent reply	other threads:[~2019-08-28  9:04 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-26  2:43 [PATCH 00/11] hashmap: bugfixes, safety fixes, and WIP improvements Eric Wong
2019-08-26  2:43 ` [PATCH 01/11] diff: use hashmap_entry_init on moved_entry.ent Eric Wong
2019-08-27 13:31   ` Derrick Stolee
2019-08-26  2:43 ` [PATCH 02/11] packfile: use hashmap_entry in delta_base_cache_entry Eric Wong
2019-08-26  2:43 ` [PATCH 03/11] hashmap_entry_init takes "struct hashmap_entry *" Eric Wong
2019-08-27 13:35   ` Derrick Stolee
2019-08-28 15:01     ` Johannes Schindelin
2019-08-30 19:48       ` Eric Wong
2019-09-02 13:46         ` Johannes Schindelin
2019-08-26  2:43 ` [PATCH 04/11] hashmap_entry: detect improper initialization Eric Wong
2019-08-27  9:10   ` Johannes Schindelin
2019-08-27  9:49     ` Eric Wong
2019-08-27 22:16       ` Junio C Hamano
2019-08-28 15:04         ` Johannes Schindelin
2019-08-28  9:03       ` Phillip Wood [this message]
2019-08-30 19:52         ` Eric Wong
2019-09-08  7:49   ` [RFC 04/11] coccicheck: detect hashmap_entry.hash assignment Eric Wong
2019-09-09 18:15     ` Junio C Hamano
2019-08-26  2:43 ` [PATCH 05/11] hashmap_get_next takes "const struct hashmap_entry *" Eric Wong
2019-08-26  2:43 ` [PATCH 06/11] hashmap_add takes "struct " Eric Wong
2019-08-26  2:43 ` [PATCH 07/11] hashmap_get takes "const struct " Eric Wong
2019-08-26  2:43 ` [PATCH 08/11] hashmap_remove " Eric Wong
2019-08-26  2:43 ` [PATCH 09/11] hashmap_put takes "struct " Eric Wong
2019-08-26  2:43 ` [PATCH 10/11] introduce container_of macro Eric Wong
2019-08-27 14:49   ` Derrick Stolee
2019-08-28  9:11     ` Phillip Wood
2019-08-30 19:43     ` Eric Wong
2019-08-26  2:43 ` [PATCH 11/11] hashmap_get_next returns "struct hashmap_entry *" Eric Wong
2019-08-27 14:53   ` Derrick Stolee
2019-08-30 19:36     ` Eric Wong
2019-09-24  1:03 ` [PATCH v2 00/19] hashmap bug/safety/ease-of-use fixes Eric Wong
2019-09-24  1:03   ` [PATCH v2 01/19] diff: use hashmap_entry_init on moved_entry.ent Eric Wong
2019-09-24  1:03   ` [PATCH v2 02/19] coccicheck: detect hashmap_entry.hash assignment Eric Wong
2019-09-25 12:44     ` Derrick Stolee
2019-09-24  1:03   ` [PATCH v2 03/19] packfile: use hashmap_entry in delta_base_cache_entry Eric Wong
2019-09-24  1:03   ` [PATCH v2 04/19] hashmap_entry_init takes "struct hashmap_entry *" Eric Wong
2019-09-25 12:48     ` Derrick Stolee
2019-09-24  1:03   ` [PATCH v2 05/19] hashmap_get_next takes "const struct " Eric Wong
2019-09-24  1:03   ` [PATCH v2 06/19] hashmap_add takes "struct " Eric Wong
2019-09-24  1:03   ` [PATCH v2 07/19] hashmap_get takes "const struct " Eric Wong
2019-09-25 12:52     ` Derrick Stolee
2019-09-30  9:57       ` Eric Wong
2019-09-24  1:03   ` [PATCH v2 08/19] hashmap_remove " Eric Wong
2019-09-25 12:54     ` Derrick Stolee
2019-09-24  1:03   ` [PATCH v2 09/19] hashmap_put takes "struct " Eric Wong
2019-09-24  1:03   ` [PATCH v2 10/19] introduce container_of macro Eric Wong
2019-09-25 13:12     ` Derrick Stolee
2019-09-30 10:39       ` Eric Wong
2019-09-24  1:03   ` [PATCH v2 11/19] hashmap_get_next returns "struct hashmap_entry *" Eric Wong
2019-09-25 13:05     ` Derrick Stolee
2019-09-24  1:03   ` [PATCH v2 12/19] hashmap: use *_entry APIs to wrap container_of Eric Wong
2019-09-25 13:15     ` Derrick Stolee
2019-09-24  1:03   ` [PATCH v2 13/19] hashmap_get{,_from_hash} return "struct hashmap_entry *" Eric Wong
2019-09-24  1:03   ` [PATCH v2 14/19] hashmap_cmp_fn takes hashmap_entry params Eric Wong
2019-09-24  1:03   ` [PATCH v2 15/19] hashmap: use *_entry APIs for iteration Eric Wong
2019-09-24  1:03   ` [PATCH v2 16/19] hashmap: hashmap_{put,remove} return hashmap_entry * Eric Wong
2019-09-24  1:03   ` [PATCH v2 17/19] hashmap: introduce hashmap_free_entries Eric Wong
2019-09-24  1:03   ` [PATCH v2 18/19] OFFSETOF_VAR macro to simplify hashmap iterators Eric Wong
2019-09-30 16:58     ` Junio C Hamano
2019-10-04  1:18     ` Junio C Hamano
2019-10-04  2:51       ` Eric Wong
2019-10-04  3:29         ` Junio C Hamano
2019-10-04 17:26           ` Eric Wong
2019-10-06  0:04             ` Junio C Hamano
2019-09-24  1:03   ` [PATCH v2 19/19] hashmap: remove type arg from hashmap_{get,put,remove}_entry Eric Wong
2019-09-25 12:42     ` Derrick Stolee
2019-09-25 13:30   ` [PATCH v2 00/19] hashmap bug/safety/ease-of-use fixes Derrick Stolee
2019-09-26  8:39   ` Johannes Schindelin
2019-09-30 10:01     ` Eric Wong
2019-09-26 13:48   ` Phillip Wood
2019-09-29  9:22   ` Junio C Hamano

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