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From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: Johannes Sixt <j6t@kdbg.org>, Carlo Arenas <carenas@gmail.com>,
	Ramsay Jones <ramsay@ramsayjones.plus.com>,
	Thomas Gummerer <t.gummerer@gmail.com>,
	GIT Mailing-list <git@vger.kernel.org>
Subject: Re: [PATCH] range-diff: fix some 'hdr-check' and sparse warnings
Date: Tue, 16 Jul 2019 16:01:01 -0400	[thread overview]
Message-ID: <20190716200101.GA6558@sigill.intra.peff.net> (raw)
In-Reply-To: <xmqqo91t3itl.fsf@gitster-ct.c.googlers.com>

On Tue, Jul 16, 2019 at 12:01:10PM -0700, Junio C Hamano wrote:

> And that "quiet and nice" form is a moral equivalent of
> 
> 	struct foo foo = { 0 };
> 
> that has been discussed in this thread.  I'd rather not to see it
> turned into distinct FOO_INIT, BAR_INIT, etc. to force the reader to
> think these structures all need their specific initialization and
> wonder what's the reason for each of them.

I'm on the fence for that style myself. But we've definitely been
trending in that direction. Look at `git grep _INIT *.h`, many of which
are clearly zero-initializers.

I do think it's nice to be able to modify the initializers later and
feel confident that you're catching all of the users. But even then:

  - it's not like we get any kind of static warning for a
    zero-initialized variant (be it static or with a manual {0}
    initializer)

  - I know I've run into problems where code assumed memset() worked,
    but it didn't (I think diff_options was one such case).

So at best it's "feel more confident", not "feel confident". :)

> One universal "struct foo foo = STRUCT_ZERO_INIT;" that is applied
> to all kinds of structure I could live with (but only if we have a
> good way to squelch sparse from bitching about it).  Perhaps we
> could define it as "{}" for GCC, while keeping it "{ 0 }" for
> others.  As I said, { 0 } is undefensible if we insist that a null
> pointer must be spelled NULL and not 0 (as CodingGuidelines says),
> but as long as we declare that we take "{ 0 }" as a mere convention
> (like we used to use the "int foo = foo;" convention to squelch
> "uninitialized but used" warnings) that is outside the purview of
> language-lawyers, I am perfectly fine with it, and if it is hidden
> behind a macro, that would be even better ;-)

Yeah, I am OK with that. My big question is if we use "{}" for gcc (and
compatible friends), does that squelch all of the complaints from other
compilers and tools that might see the "{0}" version? In particular,
does it work for sparse?

-Peff

  reply	other threads:[~2019-07-16 20:01 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-11 22:03 [PATCH] range-diff: fix some 'hdr-check' and sparse warnings Ramsay Jones
2019-07-12  5:21 ` Johannes Sixt
2019-07-12 16:44   ` Junio C Hamano
2019-07-13 10:44     ` Johannes Sixt
2019-07-13 12:18       ` Johannes Sixt
2019-07-13 12:56       ` Carlo Arenas
2019-07-13 21:29       ` Junio C Hamano
2019-07-13 22:22         ` Carlo Arenas
2019-07-14  0:51           ` Jeff King
2019-07-14  8:30             ` Johannes Sixt
2019-07-15 14:46               ` Jeff King
2019-07-15 17:30                 ` Johannes Sixt
2019-07-15 18:15                   ` Jeff King
2019-07-16 19:01                     ` Junio C Hamano
2019-07-16 20:01                       ` Jeff King [this message]
2019-07-17 18:13                         ` Junio C Hamano
2019-07-17 19:21                           ` Jeff King
2019-07-17 20:10                             ` Junio C Hamano
2019-07-17 17:23                       ` Johannes Sixt
2019-07-15 14:47           ` Johannes Schindelin
2020-10-02 17:03             ` Junio C Hamano
2020-10-04 18:35               ` Johannes Schindelin
2019-07-14  8:15         ` Johannes Sixt

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