From: Eric Wong <e@80x24.org>
To: Derrick Stolee <stolee@gmail.com>
Cc: Junio C Hamano <gitster@pobox.com>, git@vger.kernel.org
Subject: Re: [PATCH 10/11] introduce container_of macro
Date: Fri, 30 Aug 2019 19:43:08 +0000 [thread overview]
Message-ID: <20190830194308.skgeqzj7goh6y6nm@dcvr> (raw)
In-Reply-To: <381dd52f-f7d4-3e6c-24b8-22c8a0710f25@gmail.com>
Derrick Stolee <stolee@gmail.com> wrote:
> On 8/25/2019 10:43 PM, Eric Wong wrote:
> > + * container_of - Get the address of an object containing a field.
> > + *
> > + * @ptr: pointer to the field.
> > + * @type: type of the object.
> > + * @member: name of the field within the object.
> > + */
> > +#define container_of(ptr, type, member) \
> > + ((type *) ((char *)(ptr) - offsetof(type, member)))
> > +
> > #endif
>
> I think it would be good to include at least one use of this
> macro in this patch. As it stands, I need to look at the next
> patch to make sense of what this is doing.
Yeah, I considered making list_entry an alias of this.
But I wasn't sure about including git-compat-util.h in
list.h...
> It took me a little while to parse what is happening here.
> 'ptr' is a pointer to the generic struct (in our case,
> 'struct hashmap_entry *'), while 'type' is the parent type,
> and 'member' is the name of the member in 'type' that is
> of type typeof(*ptr).
>
> Perhaps this is easier to grok for others than it was for me.
*shrug* I only dabble in C, but I've been using it for a good
while. I'm probably drawn to it because I'm not a great C
programmer like having it to prevent mistakes. I also find
open-coded linked lists (even singly-linked ones!)
hard-to-follow, so I always reach for something like urcu/list.h
or ccan/list.h.
next prev parent reply other threads:[~2019-08-30 19:43 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
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 [this message]
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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