From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, "René Scharfe" <l.s.r@web.de>
Subject: Re: [PATCH 7/8] interpret-trailers: mark unused "unset" parameters in option callbacks
Date: Thu, 31 Aug 2023 13:56:38 -0400 [thread overview]
Message-ID: <20230831175638.GC3208283@coredump.intra.peff.net> (raw)
In-Reply-To: <xmqq4jkfxhx2.fsf@gitster.g>
On Thu, Aug 31, 2023 at 10:04:09AM -0700, Junio C Hamano wrote:
> Jeff King <peff@peff.net> writes:
>
> > There are a few parse-option callbacks that do not look at their "unset"
> > parameters, but also do not set PARSE_OPT_NONEG. At first glance this
> > seems like a bug, as we'd ignore "--no-if-exists", etc.
> >
> > But they do work fine, because when "unset" is true, then "arg" is NULL.
> > And all three functions pass "arg" on to helper functions which do the
> > right thing with the NULL.
>
> Yuck. That is ugly.
Yep. I wondered about adding a comment here warning about the situation,
but it felt kind of content-less. Something like:
/* if unset, arg is NULL and handled below */
trailer_set_where(opt->value, arg);
> > Note that this shortcut would not be correct if any callback used
> > PARSE_OPT_NOARG (in which case "arg" would be NULL but "unset" would be
> > false). But none of these do.
>
> That is even uglier. Unlike the BUG_ON_OPT_NEG() and BUG_ON_OPT_ARG()
> that catch discrepancies between options[] flags and the expectation
> by the callback function, there is no way for us to protect against
> such mistakes?
I guess it would be something like:
if (!unset && !arg)
BUG("unexpected use of PARSE_OPT_OPTARG");
I think it is less important than those other ones, though, because the
mistake here is the OPT_CALLBACK declaration adding a flag that the
callback is not prepared to handle. Whereas in the other ones, the bug
is that the declaration _forgot_ to use a flag, which is a much more
likely bug.
So I dunno. If it were more than this one case (well, three, but they
are all of the same form) I'd be more worried.
-Peff
next prev parent reply other threads:[~2023-08-31 17:56 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-31 7:09 [PATCH 0/8] more unused parameters in parseopt callbacks Jeff King
2023-08-31 7:12 ` [PATCH 1/8] merge: make xopts a strvec Jeff King
2023-08-31 7:22 ` Jeff King
2023-08-31 11:18 ` Phillip Wood
2023-08-31 15:46 ` Junio C Hamano
2023-08-31 20:55 ` Taylor Blau
2023-08-31 7:14 ` [PATCH 2/8] merge: simplify parsing of "-n" option Jeff King
2023-08-31 15:56 ` Junio C Hamano
2023-08-31 7:17 ` [PATCH 3/8] parse-options: prefer opt->value to globals in callbacks Jeff King
2023-08-31 16:14 ` Junio C Hamano
2023-08-31 7:18 ` [PATCH 4/8] parse-options: mark unused "opt" parameter " Jeff King
2023-08-31 16:33 ` Junio C Hamano
2023-08-31 17:50 ` Jeff King
2023-08-31 20:48 ` Jeff King
2023-08-31 7:18 ` [PATCH 5/8] merge: do not pass unused opt->value parameter Jeff King
2023-08-31 16:53 ` Junio C Hamano
2023-08-31 7:19 ` [PATCH 6/8] parse-options: add more BUG_ON() annotations Jeff King
2023-08-31 16:58 ` Junio C Hamano
2023-08-31 7:19 ` [PATCH 7/8] interpret-trailers: mark unused "unset" parameters in option callbacks Jeff King
2023-08-31 17:04 ` Junio C Hamano
2023-08-31 17:56 ` Jeff King [this message]
2023-08-31 7:20 ` [PATCH 8/8] parse-options: mark unused parameters in noop callback Jeff King
2023-08-31 17:05 ` Junio C Hamano
2023-08-31 21:16 ` [PATCH v2 0/10] more unused parameters in parseopt callbacks Jeff King
2023-08-31 21:17 ` [PATCH v2 01/10] merge: make xopts a strvec Jeff King
2023-08-31 21:17 ` [PATCH v2 02/10] merge: simplify parsing of "-n" option Jeff King
2023-09-02 6:20 ` René Scharfe
2023-09-05 6:43 ` Jeff King
2023-08-31 21:17 ` [PATCH v2 03/10] format-patch: use OPT_STRING_LIST for to/cc options Jeff King
2023-08-31 21:20 ` [PATCH v2 04/10] checkout-index: delay automatic setting of to_tempfile Jeff King
2023-08-31 22:12 ` Junio C Hamano
2023-09-02 6:20 ` René Scharfe
2023-09-05 7:12 ` [PATCH v3 " Jeff King
2023-08-31 21:21 ` [PATCH v2 05/10] parse-options: prefer opt->value to globals in callbacks Jeff King
2023-09-02 7:34 ` René Scharfe
2023-09-05 6:52 ` Jeff King
2023-08-31 21:21 ` [PATCH v2 06/10] parse-options: mark unused "opt" parameter " Jeff King
2023-09-02 10:12 ` René Scharfe
2023-09-05 7:05 ` Jeff King
2023-09-19 7:42 ` René Scharfe
2023-08-31 21:21 ` [PATCH v2 07/10] merge: do not pass unused opt->value parameter Jeff King
2023-08-31 21:21 ` [PATCH v2 08/10] parse-options: add more BUG_ON() annotations Jeff King
2023-08-31 21:22 ` [PATCH v2 09/10] interpret-trailers: mark unused "unset" parameters in option callbacks Jeff King
2023-08-31 21:22 ` [PATCH v2 10/10] parse-options: mark unused parameters in noop callback Jeff King
2023-09-02 11:37 ` René Scharfe
2023-09-05 7:09 ` Jeff King
2023-09-07 20:20 ` René Scharfe
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