Re: [PATCH 05/27] object-store: move packed_git and packed_git_mru to object store

From: Junio C Hamano <gitster@pobox.com>
Date: Feb 21, 2018, 21:51 UTC
Message-ID: <xmqqy3jmxb8s.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20180221015430.96054-6-sbeller@google.com>

Stefan Beller <sbeller@google.com> writes:

Show 9 quoted lines

> +
> +/*
> + * The mru list_head is supposed to be initialized using
> + * the LIST_HEAD macro, assigning prev/next to itself.
> + * However this doesn't work in this case as some compilers dislike
> + * that macro on member variables. Use NULL instead as that is defined
> + * and accepted, deferring the real init to prepare_packed_git_mru(). */
> +#define __MRU_INIT { NULL, NULL }
> +#define RAW_OBJECT_STORE_INIT { NULL, NULL, __MRU_INIT, NULL, NULL }

I do not think it has to be this way to abuse two NULLs, if you faithfully mimicked how LIST_HEAD() macro is constructed. The reason why it does not try to introduce

	struct list_head x = LIST_HEAD_INIT;

and instead, uses

	LIST_HEAD(x);

is because of the need for self referral. If we learn from it, we can do the same, i.e. instead of doing

	struct raw_object_store x = RAW_OBJECT_STORE_INIT;

we can do

	RAW_OBJECT_STORE(x);

that expands to

	struct raw_object_store x = {
		...
		{ &x.packed_git_mru, &x.packed_git_mru },
		...
	};

no? Then we do not need such a lengthy comment that reads only like an excuse ;-)