Re: [[PATCH v2] 1/4] patch-ids: stop using a hand-rolled hashmap implementation

From: Eric Wong <e@80x24.org>
Date: Aug 1, 2016, 22:34 UTC
Message-ID: <20160801223447.GA10924@whir>
In-Reply-To: <xmqqy44gi7bp.fsf@gitster.mtv.corp.google.com>

Junio C Hamano <gitster@pobox.com> wrote:

Show 7 quoted lines

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> 
> > It would be a serious bug if hashmap_entry_init() played games with
> > references, given its signature (that this function does not have any
> > access to the hashmap structure, only to the entry itself):
> >
> > 	void hashmap_entry_init(void *entry, unsigned int hash)

<snip>

> I have a slight preference to avoid the lazy "void *", but that is
> an unrelated tangent.

Me too. I noticed this while working on the http-walker speedups and my self-rejected last patch:

  https://public-inbox.org/git/20160711210243.GA1604%40whir/

Extracting list_entry from list.h (currently in next[1]) and exposing that generically as "container_of" for use with hashmap_* would make it safer-to-use and allow structs to belong to multiple hashmaps.

list_entry is also an alias for container_of in the Linux kernel, but we don't have enough code using list_* to warrant two names for the same macro.

[1] https://public-inbox.org/git/20160711205131.1291-4-e%4080x24.org/