From: Felipe Contreras <felipe.contreras@gmail.com>
Date: Thu, 11 May 2023 18:39:05 GMT
Subject: Re: [PATCH 23/24] hash-ll, hashmap: move oidhash() to hash-ll
Message-ID: <645d3649c6c7a_2606922942e@chronos.notmuch>
In-Reply-To: <20230511183143.GA1978320@coredump.intra.peff.net>

Jeff King wrote:

>   khash.h lets you instantiate custom hash types that map between two
>   types. These are defined as a struct, as you might expect, and khash
>   typedef's that to kh_foo_t. But it declares the struct anonymously,
>   which doesn't give a name to the struct type itself; there is no
>   "struct kh_foo". This has two small downsides:
> 
>     - when using khash, we declare "kh_foo_t *the_foo".  This is
>       unlike our usual naming style, which is "struct kh_foo *the_foo".
> 
>     - you can't forward-declare a typedef of an unnamed struct type in
>       C. So we might do something like this in a header file:
> 
>          struct kh_foo;
>          struct bar {
>                  struct kh_foo *the_foo;
> 	 };
> 
>       to avoid having to include the header that defines the real
>       kh_foo. But that doesn't work with the typedef'd name. Without the
>       "struct" keyword, the compiler doesn't know we mean that kh_foo is
>       a type.

One of the reasons why Linux doesn't do typedef.

-- 
Felipe Contreras