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From: Junio C Hamano <gitster@pobox.com>
To: "Linus Arver via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org,  Christian Couder <chriscool@tuxfamily.org>,  Emily
 Shaffer <nasamuffin@google.com>,  Josh Steadmon <steadmon@google.com>,
  "Randall S. Becker" <rsbecker@nexbridge.com>,  Christian Couder
 <christian.couder@gmail.com>,  Kristoffer Haugsbakk
 <code@khaugsbakk.name>,  Linus Arver <linusa@google.com>
Subject: Re: [PATCH v2 7/8] trailer: make trailer_info struct private
In-Reply-To: <0e9ae049b8861fecf49c097e8d52e734f7a9c9b3.1713504153.git.gitgitgadget@gmail.com>
	(Linus Arver via GitGitGadget's message of "Fri, 19 Apr 2024 05:22:32
	+0000")
References: <pull.1696.git.1710570428.gitgitgadget@gmail.com>
	<pull.1696.v2.git.1713504153.gitgitgadget@gmail.com>
	<0e9ae049b8861fecf49c097e8d52e734f7a9c9b3.1713504153.git.gitgitgadget@gmail.com>
Date: Tue, 23 Apr 2024 16:27:08 -0700
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"Linus Arver via GitGitGadget" <gitgitgadget@gmail.com> writes:

> There are a couple disadvantages:
>
>   (A) every time the member of the struct is accessed an extra pointer
>       dereference must be done, and
>
>   (B) for users of trailer_info outside trailer.c, this struct can no
>       longer be allocated on the stack and may only be allocated on the
>       heap (because its definition is hidden away in trailer.c) and
>       appropriately deallocated by the user.

    (C) without good documentation on the API, the opaque struct is
        hostile to programmers by going opposite to "Show me your
        data structures, and I won't usually need your code; it'll
        be obvious." mantra.

The comment inside trailer.c does not count (the API users are not
supposed to peek in it---that's the whole point of making the
structure opaque).  You'd need to compensate with a bit more doc in
trailer.h to help the API users.

Other than that, looks "correct".