Re: [PATCH v3 2/2] setup: fix memory leaks with `struct repository_format`

From: "Martin Ågren" <martin.agren@gmail.com>
To: Jeff King <peff@peff.net>
Cc: Git Mailing List <git@vger.kernel.org>,
	"brian m . carlson" <sandals@crustytoothpaste.net>
Subject: Re: [PATCH v3 2/2] setup: fix memory leaks with `struct repository_format`
Date: Mon, 25 Feb 2019 20:21:07 +0100	[thread overview]
Message-ID: <CAN0heSq=0=B-FoPWcuRxp0oJ6capo3Pu4txZZOP2uDeNn5N1Og@mail.gmail.com> (raw)
In-Reply-To: <20190125195107.GA6520@sigill.intra.peff.net>

On Fri, 25 Jan 2019 at 20:51, Jeff King <peff@peff.net> wrote:
>
> > On Wed, 23 Jan 2019 at 06:57, Jeff King <peff@peff.net> wrote:
> > >
> > > On Tue, Jan 22, 2019 at 10:45:48PM +0100, Martin Ågren wrote:
> > >
> > > > Call `clear_...()` at the start of `read_...()` instead of just zeroing
> > > > the struct, since we sometimes enter the function multiple times. This
> > > > means that it is important to initialize the struct before calling
> > > > `read_...()`, so document that.
> > >
> > > This part is a little counter-intuitive to me. Is anybody ever going to
> > > pass in anything except a struct initialized to REPOSITORY_FORMAT_INIT?

> > > If so, might it be kinder for read_...() to not assume anything about
> > > the incoming struct, and initialize it from scratch? I.e., not to use
> > > clear() but just do the initialization step?
>
> I'm less worried about out-of-tree users, and more concerned with just
> having a calling convention that matches usual conventions (and is
> harder to get wrong).
>
> It's a pretty minor point, though, so I can live with it either way.

It's time to resurrect this thread. I've reworked this patch to avoid
the compound literal when re-initing a struct, and I've been going back
and forth on this point about having to initialize to `..._INIT` or risk
crashing. And I keep coming back to thinking that it's not *that*
different from how `STRBUF_INIT` works.

There's the obvious difference that there aren't as many functions to
call, so there's certainly a difference in scale. And you'd think that
you'll always start with `read_...()`, but another potential first
function to call is `clear_...()` (see builtin/init-db.c), in which case
you better have used `..._INIT` first.

I'm tempted to address this point by documenting as good as I can in the
.h-file that one has to use this initializer macro. I'll obviously
convert all users, so copy-paste programming should work fine...

How does that sound to you?

Martin